The Navy Department Library
The Submarine Turtle
Naval Documents of the Revolutionary War
Presented here is a collection of documents that concern the submersible Turtle, the world’s first combat submarine. Named Turtle because its inventor, David Bushnell, believed the craft resembled “two upper tortoise shells of equal size, joined together,” it saw action in the first days of the American Revolution. Designed in 1771-1775 while Bushnell was a Yale College undergraduate, it embodied the four basic requirements for a successful military submarine: the ability to submerge; the ability to maneuver under water; the ability to maintain an adequate air supply to support the operator of the craft; and the ability to carry out effective offensive operations against an enemy surface vessel.
To achieve these requirements, Bushnell devised a number of important innovations. Turtle was the first submersible to use water as ballast for submerging and raising the submarine. To maneuver under water, Turtle was the first submersible to use a screw propeller. Bushnell was also the first to equip a submersible with a breathing device. Finally, the weaponry of Turtle, which consisted of a “torpedo,” or mine that could be attached to the hull of the target ship, was innovative as well. Bushnell was the first to demonstrate that gunpowder could be exploded under water and his mine was the first “time bomb,” allowing the operator of the Turtle to attach the mine and then to retire a safe distance before it detonated.
Bushnell had devised Turtle as a means of breaking the British blockade of Boston harbor but because of problems with the vessel, detailed in the letters of Dr. Benjamin Gale to Silas Deane, 7 December 1775 and 1 February 1776 and reproduced here, the British fleet had departed from that harbor before Turtle was operational. The first attack on an enemy vessel by Turtle took place in New York harbor in September 1776. Turtle functioned as anticipated, but the attack, for reasons detailed in the account taken from the report of David Bushnell of October 1787 and from the journal of James Thacher, October 1776, both reproduced here, did not succeed. Two subsequent attempts to attack British warships were thwarted by navigational issues and tides. Before Turtle could be re-deployed, it was sunk along with the sloop transporting it by enemy fire on 9 October 1776. Although recovered, Turtle saw no further service. Its eventual fate remains a mystery.
Although it did not achieve military success, Turtle was seen by men of the time as a revolutionary development. In 1785, George Washington wrote Thomas Jefferson: “I then thought, and still think, that it was an effort of genius.” The problem with Turtle, as the former head of the Naval Historical Center, Admiral Ernest M. Eller wrote, was Bushnell’s expectation that just one man could “carry out the combined duties of diving officer, navigator, torpedoman, and engineer, while at the same time fighting tides and currents and propelling the boat with his own muscles.”
While a submarine “practical” for warfare with range, power and reliability had to await the coming of the mechanical age, Turtle was an indispensable first step, which made future developments possible.
Source: Barber, Francis M., Lecture on Submarine Boats and their Application to Torpedo Operations. Newport, R.I.: U.S. Torpedo Station, 1875.
TABLE OF CONTENTS
1) Dr. Benjamin Gale to Silas Deane, 9 November 1775.
2) Dr. Benjamin Gale to Silas Deane, 22 November 1775.
3) Dr. Benjamin Gale to Silas Deane, 7 December 1775.
4) Dr. Benjamin Gale to Silas Deane, 1 February 1776.
5) Minutes of the Connecticut Council of Safety, 2 February 1776.
6) Military Journal of James Thacher, October, 1776.
7) Military Journal of James Thacher, 10 February 1778.
8) Thomas Jefferson to George Washington, 17 July 1785.
9) George Washington to Thomas Jefferson, 16 September 1785.
10) David Bushnell to Ezra Stiles, 16 October 1787.
11) David Bushnell to Thomas Jefferson, 13 October 1787, with enclosures.
12) Ezra Lee to David Humphreys, 20 February 1815, with explanatory notes apparently added by Humphreys.
(1) Dr. Benjamin Gale to Silas Deane
|Dear Sir.-||Killingworth, 9th Nov., 1775.|
In your last you requested I would give you an account of the progress of our machine, and whether anything may be expected of it. I now sit down to give you a succinct but imperfect account of its structure, which is so complicated that it is impossible to give a perfect idea of it.
The Body, when standing upright in the position in which it is navigated, has the nearest resemblance to the two upper shells of a Tortoise joined together. In length it doth not exceed 7-1/2 feet from the stem to the higher part of the rudder: the height not exceeding 6 feet. The person who navigates it enters at the top. It has a brass top or cover, which receives the person's head as he sits on a seat, and is fastened on the inside by screws. In this brass head is fixed eight glasses, viz. two before, two on each side, one behind, and one to look out upwards. In the same brass head are fixed two brass tubes, to admit fresh air when requisite, and a ventilator at the side to free the machine from the air rendered unfit for respiration. On the inside is fixed a Barometer, by which he can tell the depth he is under water; a Compass, by which he knows the course he steers. In the barometer and on the needles of the compass is fixed fox-fire, i.e. wood that gives light in the dark. His ballast consists of about 900 wt. of lead which he carried at the bottom and on the outside of the machine, part of which is so fixed as he can let run down to the Bottom, and serves as an anchor, by which he can ride ad libitum. He has a sounding lead fixed at the bow, by which he can take the depth of water under him; and to bring the machine into a perfect equilibrium with the water, he can admit so much water as is necessary, and has a forcing pump by which he can free the machine at pleasure, and can rise above water, and again immerge, as occasion requires.
In the bow, he has a pair of oars fixed like the two opposite arms of a wind mill, with which he can row forward, and turning them the opposite way, row the machine backward; another pair fixed upon the same model, with which he can row the machine round, either to the right or left, and a third, by which he can row the machine either up or down; all which are turn'd by foot, like a spinning wheel. The rudder by which he steers, he manages by hand, within board. All these shafts which pass through the machine are so curiously fix'd as not to admit any water to incommode the machine. The magazine for the powder is carried on the hinder part of the machine, without board, and so contrived, that when he comes under the side of the Ship, he rubs down the side until he comes to the keel, and a hook so fix'd as that when it touches the keel it raises a spring which frees the magazine from the machine and fastens it to the side of the Ship; at the same time, it draws a pin, which sets the watchwork agoing which, at a given time, springs the lock and the explosion ensues.
Three magazines are prepared; the first, the explosion takes place in twelve, - the second in eight, - the third in six hours, after being fixed to the ship. He proposes to fix these three before the first explosion takes place. He has made such a trial of the effects of the explosion of gunpowder under water, since Dr. [Benjamin] Franklin did me the honor to call upon me, as has exceeded his most sanguine expectations, and is now convinced his magazines will contain three times so much powder as is necessary to destroy the largest ship in the navy.
I now write with the greater freedom, as I conclude by the time this reaches you the machine will be in camp. Lately he has conducted matters and his designs with the greatest secrecy, both for the personal safety of the navigator as to produce the greatest astonishment to those against whom it is designed, - if this projection succeeds, of which I make no doubt, as I well know the man and have seen the machine while in embryo, and every addition made to it fills me with fresh astonishment and surprize. And you may call me a visionary, an enthusiast, or what you please, - I do insist upon it, that I believe the inspiration of the Almighty has given him understanding for this very purpose and design. If he succeeds, a stipend for life, and if he fails, a reasonable compensation for time and expense is his due from the public.
What astonishment it will produce and what advantages may be made by those on the spot, if it succeeds, is more easy for you to conceive than for me to describe.
I congratulate you and my country in the begun success of our Arms to the northward, and the prospects of further success. Make my most respectful compliments to Dr. Franklin and our Delegates, your associates; and am, most respectfully Your sincere friend and most humble servt,
Source: Silas, Deane. "Correspondence of Silas Deane Delegate to the Congress at Philadelphia, 1774-1776," Collections of the Connecticut Historical Society. Hartford, CT, 1860-, 2: 315-18.
(2) Dr. Benjamin Gale to Silas Deane
|Killingworth, Nov. 22d, 1775.|
Sir, - I have to ask pardon for the wrong information I gave you. At the time of my last writing, I supposed the Machine was gone, but since find one proving the navigation of it in Connecticut River. The forcing pump made by Mr. Doolittle, not being made according to order given, did not answer; which has delayed him [David Bushnell]. The trials I mentioned to have been made since Dr. Franklin's being here, was the explosion, which prov'd beyond expectation.
I suppose he sets off this day with his new constructed pump, in order to prove the navigation, and if not prevented by ice in the River, will proceed soon. So far as you may have made known the contents of my letter, you may add this supplement.
He is by no means discouraged in the attempt. I had not seen him myself since Dr. Franklin was here, as his movement I had only from common report but have since seen him myself. But few know the cause of his present delay.
Source: "Correspondence of Silas Deane," Collections of the Connecticut Historical Society, 2: 322-23.
(3) Dr. Benjamin Gale to Silas Deane
|Killingworth, 7th Dec., 1775.|
Dear Sir, - According to your request I wrote you sometime since respecting our machine, supposing it was gone to the eastward. On finding that on proof of the navigation one instrument failed performing what was expected from it I then by letter acquainted you the proceeding was delayed until that could be repaired; which when done, another proof has been made which answers well, and every trial made requisite to the attempt respecting navigation, and everything answers well, but still, he fails on one account. He proposes going in the night, on account of safety. He always depends on fox-wood, which gives light in the dark, to fix on the points of the needle of his compass, and in his barometer, by which he may know what course to steer and the depth he is under water, both which are absolute necessity for personal safety of the navigator; but he now finds that the frost wholly destroys that quality in that wood, of which he was before ignorant, and for that reason and that alone he is obliged to desist. He was detained near two months for want of money, and before he could obtain it the season was so far advanced he was, in the manner I have now related, frustrated. I write you this with two views, first that you and those to whom you may have communicated what I wrote, may not think I have imposed upon you an idle story, and in the next place to have you enquire of Dr. Franklin w[hethe]r he knows of any kind of phosphorus which will give light in the dark and not consume the air. He has tried a candle, but that destroys the air so fast he cannot remain under water long enough to effect the thing. This you may rely upon, he has made every requisite experiment in proof of the machine, and it answers expectations; what I mentioned above is only wanting ....
The person, the inventor of this machine, now makes all his affairs a secret even to his best friends, and I have liberty to communicate this much from him only with a view to know if Dr. Franklin knows of any kind of phosphorus that will answer his purpose; otherwise the execution must be omitted until next spring, after the frosts are past. I am therefore to request your strictest silence in that matter. I am Sir, your humble servant
Source: "Correspondence of Silas Deane," Collections of the Connecticut Historical Society, 2: 333-335.
(4) Dr. Benjamin Gale to Silas Deane
|Killingworth, Feby 1st, 1776.|
Dear Sir, - I have to acknowledge the receipt of yours of the 13th ult. I make no doubt of your pressure by the important concerns lying before you, many of which I trust if you had leisure you might not communicate; but with regard to the matter of principal concern, if the Philosopher's Lanthorn may be attained, and will give a better light than what is proposed, should be glad you would get what knowledge you can from Dr. Franklin respecting it. Light is of absolute necessity; not to perform the operation, - that can be effected, if he hits the object right, as well in the dark as at noon day, - but to get free from the object when the operation is performed, - for this, light is absolutely necessary, what point to steer, and to know whether he rises or sinks deeper, for the personal safety of the operator. You will well understand my meaning, if I am not more explicit. I have lately seen the man, and conversed freely with him. He is no enthusiast; a perfect philosopher, and by no means doubtful of succeeding. I wish Col. Dyer and you were to remain where you are, even altho' the other gentlemen were added. I have no objection to that addition, but if I may judge from what I hear, your countrymen are not suited with your recall.
Let me hear from you on this subject as soon as you can. I may ask, and you may refuse to tell me, - Are we well provided with Warlike Stores? Shall we have, or can we have if desired Foreign Aid? What are French troops to do in the West Indies? Is there a channel of communication open with our friends at home?
By the public accounts there is some prospect of a rupture at hand. Can the British Nation suffer such wicked work, and tamely look on? I am, Dear Sir [&c.]
Source: Silas, Deane. "Correspondence of Silas Deane Delegate to the Congress at Philadelphia, 1774-1776," Collections of the Connecticut Historical Society. Hartford, CT, 1860-, 2: 358-59.
(5) Minutes of the Connecticut Council of Safety
At a meeting of the Governor and Council of Safety,
|[Lebanon] Friday, 2d, Febuary,  A.M.|
Mr. [David] Bushnell was here, by request of the Governor and Council, and gave an account of his machine contrived to blow ships &c., and was asked many questions about it &c. &c., and being retired, on consideration, voted, that we hold ourselves under obligations of secrecy about it. And his Honor the D. Governor is desired to reward him for his trouble and expence in corning here, and signifie to him that we approve of his plan and that [it] will be agreeable to have him proceed to make every necessary preparation and experiment about it, with expectation of proper public notice and reward.
Source: Charles T. Hoadly, et al., eds. The Public Records of the Colony of Connecticut. Hartford, CT: Press of the Case, Lockwood and Brainard Co., 1850-90, 15: 232, 233-34.
(6) Military Journal of James Thacher, October, 1776
October.  - By some gentlemen from head-quarters, near New York, we are amused with an account of a singular machine, invented by a Mr. D. Bushnell of Connecticut, for the purpose of destroying the British shipping by explosion. This novel machine was so ingeniously constructed, that, on examination, Major-General Putnam was decidedly of opinion that its operations might be attended with the desired success; accordingly he encouraged the inventor, and resolved to be himself a spectator of the experiment on the British shipping in New York harbor. Mr. Bushnell gave to his machine the name of American Turtle or Torpedo. It was constructed on the principles of submarine navigation, and on trial it has been ascertained that it might be rowed horizontally, at any given depth under water, and the adventurer, concealed within, might rise or sink, as occasion requires. A magazine of powder was attached to it in such a manner as to be screwed into the bottom of the ship; and being now disengaged from the machine, the operator retires in safety, leaving the internal clock work in motion; and at the distance of half an hour, or an hour, the striking of a gun lock communicates fire to the powder, and the explosion takes place. It was determined to make the experiment with this machine in the night, on the ship Eagle, of sixty-four guns on board of which admiral Lord Howe commanded. General Putnam placed himself on the wharf to witness the result. Mr. Bushnell had instructed his brother in the management of the Torpedo with perfect dexterity; but being taken sick, a sergeant of a Connecticut regiment was selected for the business, who, for want of time, could not be properly instructed. He, however, succeeded so far as to arrive in safety with his apparatus under the bottom of the ship, when the screw, designed to perforate the copper sheathing, unfortunately struck against an iron plate, near the rudder, which, with the strong current and want of skill in the operator, frustrated the enterprise; and, as day-light had begun to appear, the sergeant abandoned his magazine, and returned in the Torpedo to the shore. In less than half an hour a terrible explosion from the magazine took place, and threw into the air a prodigious column of water, resembling a great water-spout, attended with a report like thunder. General Putnam and others, who waited with great anxiety for the result, were exceedingly amused with the astonishment and alarm which this secret explosion occasioned on board of the ship. This failure, it is confidently asserted, is not to be attributed to any defect in the principles of this wonderful machine; as it is allowed to be admirably calculated to execute destruction among the shipping.
Source: James Thacher, Military Journal of the American Revolution. Hartford, CT: American Subscription Publishing House, 1862, pp. 62-3.
(7) Military Journal of James Thacher, 10 February, 1778
10th. [February 1778] - I have now obtained a particular description of the American Torpedo, and other ingenious submarine machinery, invented by Mr. David Bushnell, for the purpose of destroying shipping while at anchor, some account of which may be found in this Journal, page 62. The external appearance of the torpedo bears some resemblance to two upper tortoise shells, of equal size, placed in contact, leaving, at that part which represents the head of the animal, a flue or opening, sufficiently capacious to contain the operator, and air to support him thirty minutes. At the bottom, opposite to the entrance, is placed a quantity of lead for ballast. The operator sits upright, and holds an oar for rowing forward or backward, and is furnished with a rudder for steering. An aperture at the bottom, with its valve, admits water for the purpose of descending, and two brass forcing pumps serve to eject the water within, when necessary for ascending. The vessel is made completely water-tight, furnished with glass windows for the admission of light, with ventilators and air-pipes, and is so ballasted, with lead fixed at the bottom, as to render it solid, and obviate all danger of oversetting. Behind the submarine vessel, is a place above the rudder for carrying a large powder magazine; this is made of two pieces of oak timber, large enough, when hollowed out, to contain one hundred and fifty pounds of powder, with the apparatus used for firing it, and is secured in its place by a screw turned by the operator. It is lighter than water, that it may rise against the object to which it is intended to be fastened. Within the magazine, is an apparatus constructed to run any proposed length of time under twelve hours; when it has run out its time, it unpinions a strong lock, resembling a gun-lock, which gives fire to the powder. This apparatus is so pinioned, that it cannot possibly move, till, by casting off the magazine from the vessel, it is set in motion. The skilful operator can swim so low on the surface of the water, as to approach very near a ship in the night, without fear of being discovered; and may, if he choose, approach the stern or stem, above water, with very little danger. He can sink very quickly, keep at any necessary depth, and row a great distance in any direction he desires without coming to the surface. When he rises to the surface, he can soon obtain a fresh supply of air, and, if necessary, he may then descend again and pursue his course. Mr. Bushnell found that it required many trials and considerable instruction to make a man of common ingenuity a skilful operator. The first person, his brother, whom he employed, was very ingenious, and made himself master of the business, but was taken sick before he had an opportunity to make use of his skill. Having procured a substitute, and given him such instruction as time would allow, he was directed to try an experiment on the Eagle, a sixty-four-gun ship, on board of which Lord Howe commanded, lying in the harbor of New York. He went under the ship, and attempted to fix the wooden screw into her bottom, but struck, as he supposes, a bar of iron which passes from the rudder hinge, and is spiked under the ship's quarter. Had he moved a few inches, which he might have done without rowing, there is no doubt he would have found wood where he might have fixed the screw; or if the ship had been sheathed with copper, he might easily have pierced it. But not being well skilled in the management of the vessel, in attempting to move to another place, he lost the ship. After seeking her in vain, for some time, he rowed some distance, and rose to the surface of the water, but found day-light had advanced so far, that he durst not renew the attempt. He says that he could easily have fastened the magazine under the stern of the ship, above water, as he rowed up to the stern and touched it before he descended. Had he fastened it there, the explosion of one hundred and fifty pounds of powder, the quantity contained in the magazine, must have been fatal to the ship. In his return from the ship to New York, he passed near Governor's Island, and thought he was discovered by the enemy on the island. Being in haste, to avoid the danger he feared, he cast off the magazine, as he imagined it retarded him in the swell, which was very considerable. After the magazine had been cast off one hour, the time the internal apparatus was set to run, it blew up with great violence, throwing a vast column of water to an amazing height in the air, and leaving the enemy to conjecture whether the stupendous noise was produced by a bomb, a meteor, a water-spout, or an earthquake. Some other attempts were made in Hudson's river, in one of which the operator, in going towards the ship, lost sight of her and went a great distance beyond her, and the tide ran so strong as to baffle all his efforts. Mr. Bushnell being in ill health, and destitute of resources, was obliged to abandon his pursuit at that time, and wait for a more favorable opportunity, which never occurred. In the year 1777, Mr. Bushnell made an attempt from a whale-boat, against the Cerberus frigate lying at anchor, by drawing a machine against her side, by means of a line. The machine was loaded with powder, to be exploded by a gun-lock, which was to be unpinioned by an apparatus to be turned by being brought alongside of the frigate. This machine fell in with a schooner at anchor astern of the frigate, and concealed from his sight. By some means it became fixed, and exploding, demolished the schooner. Commodore Simmons, being on board the Cerberus, addressed an official letter to Sir Peter Parker, describing this singular disaster. Being at anchor to the westward of New London, with a schooner which he had taken, discovered about eleven o'clock in the evening a line towing astern from the bows. He believed that some person had veered away by it, and immediately began to haul in. A sailor, belonging to the schooner, taking it for a fishing line, laid hold of it, and drew in about fifteen fathoms. It was buoyed up by small pieces of wood tied to it at stated distances. At the end of the rope a machine was fastened, too heavy for one man to pull up, for it exceeded one hundred pounds in weight. The other people of the schooner coming to his assistance, they drew it on deck. While the men were examining the machine, about five minutes from the time the wheel had been put in motion, it exploded, blew the vessel into pieces, and set her on fire. Three men were killed, and the fourth blown into the water, much injured. On examining round the ship, after this accident, the other part of the line was discovered, buoyed up in the same manner. This the commodore ordered to be instantly cut away, for fear of hauling up another of the infernals, as he termed it. These machines were constructed with wheels, furnished with irons sharpened at the end, and projecting about an inch, in order to strike the sides of the vessel when hauling them up, thereby setting the wheels in motion, which in the space of five minutes causes the explosion. Had the whole apparatus been brought to operate on a ship at the same time, it must have occasioned prodigious destruction. Mr. Bushnell contrived another ingenious expedient to effect his favorite object. He fixed a large number of kegs under water, charged with powder, to explode on coming in contact with any thing while floating along with the tide. He set his squadron of kegs afloat in the Delaware, above the English shipping, in December, 1777. The kegs were in the night set adrift, to fall with the ebb, on the shipping; but the proper distance could not be well ascertained, and they were set adrift at too great a distance from the vessels, by which means they were obstructed and dispersed by the ice. They approached, however, in the daytime, and one of them blew up a boat, and others exploded, which occasioned among the British seamen the greatest alarm and consternation. They actually manned the wharves and shipping at Philadelphia, and discharged their small arms and cannon at every thing they could see floating in the river, during the ebb tide. This incident has received the name of the Battle of the Kegs, and furnished a subject for an excellent and humorous song by the Honorable Francis Hopkinson.
Source: James Thacher, Military Journal of the American Revolution. Hartford, CT: American Subscription House, 1862, pp. 122-26.
(8) Thomas Jefferson to George Washington
|Sir||Paris July 17. 1785.|
Permit me to add, what I forgot in my former letter, a request to you to be so kind as to communicate to me what you can recollect of Bushnel's experiments in submarine navigation during the late war, and whether you think his method capable of being used succesfully for the destruction of vessels of war, it's not having been actually used for this purpose by us, who were so peculiarly in want of such an agent seems to prove it did not promise success. I am with the highest esteem Sir
|your most obedt & most humble sert|
Source: Papers of Thomas Jefferson, vol. 13, Library of Congress, Washington, DC. Printed in Thomas Jefferson, The Papers of Thomas Jefferson, ed. by Julian Boyd, et al., 34 vols. to date. Princeton: Princeton University Press, 1950-, 8: 301.
(9) George Washington to Thomas Jefferson
|Mount Vernon 26th Septr. 1785|
I am sorry I cannot give you full information respecting Captn. Bushnals projects for the destruction of shipping. - No interesting experiment having been made, and my memory being treacherous, I may, in some measure, be mistaken in what I am about to relate.
Bushnel is a man of great Mechanical powers - fertile of invention - and a master in execution - He came to me in 1776 recommended by Governor Trumbull (now dead) and other respectable characters who were proselites to his plan. - Although I wanted faith myself, I furnished him with money, and other aids to carry it into execution. - He laboured for sometime ineffectually, & though the advocates for his scheme continued sanguine he never did succeed - One accident or another was always intervening. - I then thought, and still think, that it was an effort of genius; but that a combination of too many things were requisite, to expect much success from the enterprise against an enemy, who are always upon guard. - That he had a machine which was so contrived as to carry a man under water at any depth he chose, and for a considerable time & distance, with an apparatus charged with Powder which he could fasten to a ships bottom or side & give fire to in any given time (sufft. for him to retire) by means whereof a ship could be blown up, or sunk, are facts which I believe admit of little doubt - but then, where it was to operate against an enemy, it is no easy matter to get a person hardy enough to encounter the variety of dangers to which he must be exposed. 1 from the novelty 2 from the difficulty of conducting the machine, and governing it under water on acct. of the Currents &ca. 3 the consequent uncertainty of hitting the object of destination, without rising frequently above water for fresh observation, wch., when near the Vessel, would expose the adventurer to a discovery, & almost to certain death - To these causes I always ascribed the non-performance of his plan, as he wanted nothing that I could furnish to secure the success of it. - This to the best of my recollection is a true state of the case - But Humphreys, if I mistake not, being one of the proselites, will be able to give you a more perfect acct. of it than I have done ....
Source: Papers of Thomas Jefferson, vol. 13, Library of Congress, Washington, DC. Printed in Thomas Jefferson, The Papers of Thomas Jefferson, ed. by Julian Boyd, et al., 34 vols. to date. Princeton: Princeton University Press, 1950-, 8: 555-57.
(10) David Bushnell to Ezra Stiles
|Sir||Stamford October 16th 1787.|
Induced by the desire you intimated in your Letter to me, of seeing what I should write to his Excellency Governor Jefferson our Ambassador at Paris, I have together with this, inclosed a Copy of what I have sent to his Excellency. The Original is forwarded by Colonel Humphrys, a Gentleman to whom I am much indebted, who wrote more than once upon the affair, and to whose friendship, I have no doubt, I owe the attention of the Governor to the Subject, and his desire of information, agreeably to what you and Colonel Humphrys wrote long since.
I beg leave to thank you for your advice, and your kind offer to take the charge of forwarding my Letter to his Excellency. I could wish that what I have written should not come to the knowledge of the public, for the same reason, as I have written to the Governor, that I have ever wished to be silent upon the subject. Should what I have written to the Governor miscarry, I wish these might be ready to be forwarded to him, if I should be obliged to make use of them.
If you are desirous of any information which is not contained in this packet, I shall esteem it a favour, if you will give me the opportunity of satisfying you. Should you think proper to write to me or receive anything from His Excellency Governor Jefferson which respects me, I could wish they might be directed to the care of Major John Davenport in Stamford.
|I am Sir &c..-||David Bushnell|
Source: Ezra Stiles Papers, New Haven Colony Historical Society.
(11) David Bushnell to Thomas Jefferson
|Sir||Stamford, In Connecticut Octr. 13th. 1787.|
In the latter part of the year 1785, I received a Letter from Colonel David Humphrys, and soon after, another from Doctor Ezra Stiles, President of Yale College in Connecticut, informing me, that your Excellency desired an account of my Submarine Vessel, and the Experiments which I had made.
At the time I received those Letters, I was seized with a severe illness, which disabled me from writing, & though I attempted it several times, obliged me to desist. Ever since I recovered my health, my situation has been such, that until this time, it has not been in my power to write to your Excellency, upon the Subject.
I shall think myself happy if this, arriving thus late, meet with your Excellency's acceptance, and give you the information you desired; and shall only regret, that I had it not in my power to write, as soon as I received the communications of those Gentlemen.
Doctor Stiles, in his Letter to me, transcribed from yours the following, "If he thought proper to communicate it, I would engage never to disclose it, unless I could find an opportunity of doing it for his Benefit." In answer to this declaration, I shall submit the disclosure of it entirely to your Excellency, to do as you shall think proper; & beg leave to return you my sincere thanks for your generous intentions.
I have ever carefully concealed my Principles & Experiments, as much as the nature of the subject allowed, from all but my chosen Friends, being persuaded that it was the most prudent course, whether the event should prove fortunate or otherwise, although by the concealment I never fostered any great expectations of profit, or even of a compensation for my time & expences; the loss of which has been exceedingly detrimental to me.
With this your Excellency will receive a sketch of the general principles and construction of the Submarine Vessel blended together, as they occur at this time, with many of the Minutiae. I should gladly exhibit everything with the utmost minuteness, but apprehend I have not been sufficiently clear in what I have written, and have a doubt whether I could explain the whole intelligibly, without drawings, which I cannot easily execute or obtain. But should this not be sufficient, & you should wish to have a more minute description of the whole, or of any particular part not sufficiently explained here, I shall be happy to receive your Excellency's commands, and shall obey them, as soon as they come to hand, without any reserve.
As I am desirous this should not fall into improper hands, I could wish, if it were not too great a favour, to hear that this finds a safe conveyance to your Excellency.
|In the mean time, with the most respectful sentiments, I am &c|
P.S. Should your Excellency think proper to inform me of the safe arrival of this packet, I could wish such information might be directed to the care of Doctor Stiles.
His Excellency Thomas Jefferson Esquire.
Source: Papers of Thomas Jefferson, vol. 13, Library of Congress, Washington, DC. Printed in Thomas Jefferson, The Papers of Thomas Jefferson, ed. by Julian Boyd, et al., 34 vols. to date. Princeton: Princeton University Press, 1950-, 12: 303-4.
"General principles & construction of a Submarine Vessel."
No.2. The external shape of the Submarine Vessel bore some resemblance to two upper tortoise shells of equal size, joined together: the place of entrance into the Vessel being represented by the opening, made by the swell of the shells, at the head of the animal. The inside was capable of containing the Operator, and air, sufficient to supply him, thirty minutes, without receiving fresh air. At the bottom, opposite to the entrance, was fixed a quantity of lead for ballast. At one edge, which was directly before the operator, who sat upright, was an oar, for rowing forward or backward. At the other edge, was a rudder for steering. An aperture, at the bottom, with its valve, was designed to admit water for the purpose of descending; & two brass forcing pumps served to eject the water within, when necessary for ascending. At the top, there was likewise an oar, for ascending or descending, or continuing at any particular depth. A Watergage or Barometer, determined the depth of descent, a compass directed the course, & a ventilator within, supplied the Vessel with fresh air, when on the surface.
The entrance into the Vessel was elliptical, and so small, as barely to admit a person. This entrance was surrounded with a broad elliptical iron band, the lower edge of which was let into the wood of which the body of the Vessel was made, in such a manner, as to give its utmost support to the body of the Vessel against the pressure of the water. Above the upper edge of this iron band, there was a brass Crown or cover, resembling a hat with its crown and brim, which shut watertight upon the iron band: the Crown was hung to the iron band with hinges so as to turn over sidewise, when opened: to make it perfectly secure when shut, it might be screwed down upon the band by the operator, or by a person without.
There were in the brass Crown, three round doors, one directly in front, and one on each side, large enough to put the hand through, when open they admitted the fresh air; their shutters were ground perfectly tight into their places, with emery, hung with hinges, & secured in their places when shut. There were likewise several small glass windows in the Crown, for looking through, and for admitting light in the daytime, with Covers to secure them. There were two airpipes in the Crown. A ventilator within drew fresh air through one of the airpipes, and discharged it into the lower part of the Vessel; the fresh air introduced by the ventilator, expelled the impure light air through the other airpipe. Both airpipes were so constructed, that they shut themselves whenever the water rose near their tops, so that no water could enter through them, and opened themselves immediately after they rose above the water.
The Vessel was chiefly ballasted with lead, fixed to its bottom: when this was not sufficient, a quantity was placed within, more or less, according to the weight of the operator: its ballast made it so stiff, that there was no danger of oversetting. The Vessel with all its appendages, and the operator, was of sufficient weight to settle it very low in the water. About two hundred pounds of the lead at the bottom for ballast, could be let down forty or fifty feet below the Vessel: this enabled the operator to rise instantly to the surface of the water in case of accident.
When the operator would descend he placed his foot upon the top of a brass valve, depressing it, by which he opened a large aperture in the bottom of the Vessel, through which the water entered at his pleasure . When he had admitted a sufficient quantity, he descended very gradually; if he admitted too much, he ejected as much as was necessary to obtain an equilibrium, by the two brass forcing pumps, which were placed at each hand. Whenever the Vessel leaked or he would ascend to the surface, he also made use of these forcing pumps. When the skilful operator had obtained an equilibrium, he could row upward, or downward, or continue at any particular depth, with an oar, placed near the top of the Vessel, formed upon the principle of the screw, the axis of the oar entering the Vessel: by turning the oar one way he raised the Vessel, by turning it the other way he depressed it.
A glass tube eighteen inches long, and one inch in diameter, standing upright, its upper end closed, and its lower end, which was open, screwed into a brass pipe, through which the external water had a passage into the glass tube, served as a Watergage or Barometer. There was a piece of cork, with phosphorus on it, put into the Watergage: When the Vessel descended,the water rose in the watergage, condensing the air within, and bearing the cork, with its phosphorus, on its surface. By the light of the phosphorus, the ascent of the water in the gage was rendered visible, and the depth of the Vessel under water ascertained by a graduated line.
An oar, formed upon the principle of the screw, was fixed in the forepart of the Vessel, whose axis entered the Vessel, which being turned one way, rowed the Vessel forward, and being turned the other way, rowed it backward: it was made to be turned by hand or foot.
A rudder, hung to the hinder part of the Vessel, commanded it with the greatest ease. The rudder was made very elastick, and might be used for rowing forward. Its tiller was within the Vessel, at the operator's right hand, fixed, at a right angle, on an iron rod, which passed through the side of the Vessel; the rod had a crank on its outside end, which commanded the rudder, by means of a rod extending from the end of the crank to a kind of tiller, fixed upon the left hand of the rudder. Raising & depressing the first mentioned tiller turned the rudder, as the case required.
A compass marked with phosphorus directed the course, both above and under the water; & a line and lead founded the depth when necessary.
The internal shape of the Vessel, in every possible section of it, verged towards an ellipsis, as near as the design would allow, but every horizontal section, although elliptical, as near a circle, as could be admitted. The body of the Vessel was made exceedingly strong; and to strengthen it as much as possible, a firm piece of wood was framed, parallel to the conjugate diameter, to prevent the sides from yielding to the great pressure of the incumbent water in a deep immersion. This piece of wood was also a seat for the operator.
Every opening was well secured. The pumps had two sets of valves. The aperture at the bottom, for admitting water was covered with a plate perforated full of holes to receive the water, and prevent anything from choaking the passage, or stopping the valve from shutting. The brass valve might likewise be forced into its place with a screw, if necessary. The airpipes had a kind of hollow sphere, fixed round the top of each, to secure the air pipe-valves from injury; these hollow spheres were perforated full of holes for the passage of the air through the pipes: within the airpipes were shutters to secure them, should any accident happen to the pipes, or the valves on their tops.
Whenever the external apparatus passed through the body of the Vessel, the joints were round and formed by brass pipes, which were driven into the wood of the Vessel; the holes through the pipes were very exactly made, and the iron rods which passed through them were turned in a lathe to fit them; The joints were also kept full of oil to prevent rust and leaking. Particular attention was given to bring every part, necessary for performing the operations, both within and without the Vessel, before the operator, and as convenient as could be devised: so that every thing could be found in the dark, except the watergage, and the compass, which were visible by the light of the phosphorus, and nothing required the operator to turn to the right hand, or the left, to perform anything necessary.
|Description of a Magazine & its appendages, designed to be conveyed by the submarine|
|Vessel to the bottom of a Ship.|
In the forepart of the brim of the Crown of the Submarine Vessel, was a socket, and an iron tube passing through the socket; the tube stood upright, and could slide up and down in the socket, six inches: at the top of the tube, was a Woodscrew (A) fixed by means of a rod, which passed through the tube, and screwed the Woodscrew fast upon the top of the tube: by pushing the Woodscrew up against the bottom of a Ship, and turning it at the same time, it would enter the planks; driving would answer the same purpose; when the Woodscrew was firmly fixed, it could be cast off by unscrewing the rod, which fastened it upon the top of the tube.
Behind the Submarine Vessel, was a place, above the rudder, for carrying a large Powder Magazine; this was made of two pieces of oak timber, large enough, when hollowed out, to contain one hundred and fifty pounds of Powder, with the apparatus used in firing it, and was secured in its place by a screw, turned by the operator. A strong piece of rope extended from the magazine to the Woodscrew (A) abovementioned, and was fastened to both. When the Woodscrew was fixed, and to be cast off from its tube, the Magazine was to be cast off likewise by unscrewing it, leaving it hanging to the Woodscrew: it was lighter than the water that it might rise up against the object, to which the Woodscrew and itself were fastened.
Within the Magazine, was an apparatus, constructed to run any proposed length of time under twelve hours; when it had run out its time, it unpinioned a strong lock resembling a gun lock, which gave fire to the powder. This apparatus was so pinioned, that it could not possibly move till, by casting off the Magazine from the Vessel, it was set in motion.
The skilful operator could swim so low on the surface of the water, as to approach very near a Ship, in the Night, without fear of being discovered, and might if he chose, approach the stem or stern, above water, with very little danger. He could sink very quick, keep at any depth he pleased, and row a great distance, in any direction he desired, without coming to the surface; & when he rose to the surface, he would soon obtain a fresh supply of air, when, if necessary, he might descend again and pursue his course.
The above Vessel, Magazine &c. were projected in the year 1771, but not completed until the year 1775.
"Experiments made to prove the nature and use of a Submarine Vessel."
The first experiment I made, was with about two ounces of gunpowder, which I exploded four feet under water, to prove to some of the first Personages in Connecticut, that powder would take fire under water.
The second experiment was made with two pounds of powder, inclosed in a wooden bottle, and fixed under a hogshead, with a two inch oak plank between the hogshead and the powder; the hogshead was loaded with stones as deep as it could swim; a wooden pipe descending through the lower head of the hogshead, & through the plank into the powder contained in the bottle, was primed with powder. A match put to the priming exploded the powder, which produced a very great effect, rending the plank into pieces, demolishing the hogshead, and casting the stones and ruins of the hogshead, with a body of water many feet into the air, to the astonishment of the spectators. This experiment was likewise made for the satisfaction of the Gentlemen abovementioned.
I afterwards made many experiments of a similar nature; some of them with large quantities of powder; they all produced very violent explosions, much more than sufficient for any purpose I had in view.
In the first essays with the submarine Vessel, I took care to prove its strength to sustain the great pressures of the incumbent water when sunk deep, before I trusted any person to descend much below the surface: and I never suffered any person to go under water without having a strong piece of rigging made fast to it, until I found him well acquainted with the operations necessary for his safety. After that I made him descend and continue at particular depths, without rising or sinking, row by the compass, approach a Vessel, go under her, and fix the Woodscrew, mentioned in No 2, and marked A, into her Bottom, &c. until I thought him sufficiently expert to put my design into execution.
I found agreeably to my expectation, that it required many trials to make a person of common ingenuity, a skilful operator. The first I employed was very ingenious and made himself master of the business, but was taken sick in the campaign of 1776 at N.York, before he had an opportunity to make use of his skill, and never recovered his health sufficiently afterwards.
Experiments made with a submarine Vessel.
After various attempts to find an operator to my wish, I sent one, who appeared more expert than the rest, from N. York to a fifty gun Ship lying not far from Governour's Island. He went under the Ship and attempted to fix the Woodscrew into her bottom, but struck as he supposes, a bar of iron, which passes from the rudder hinge and is spiked under the Ship's quarter. Had he moved a few inches, which he might have done without rowing, I have no doubt, but he would have found wood, where he might have fixed the screw; or if the Ship were sheathed with copper, he might easily have pierced it: but, not being well skilled in the management of the Vessel, in attempting to move to another place, he lost the Ship. After seeking her in vain, for sometime, he rowed some distance, and rose to the surface of the water, but found daylight had advanced so far, that he durst not renew the attempt.
He says that he could easily have fastened the Magazine under the Stern of the Ship, above water, as he rowed up to the stern, and touched it, before he descended. Had he fastened it there, the explosion of one hundred and fifty pounds of powder, the quantity contained in the Magazine, must have been fatal to the Ship. In his return from the Ship to N. York, he passed near Governor's Island, and thought he was discovered by the Enemy, on the Island; being in hast to avoid the danger he feared, he cast off the magazine, as he imagined it retarded him, in the swell, which was very considerable. After the Magazine had been cast off, one hour, the time the internal apparatus was set to run, it blew up with great violence.
Afterwards there were two attempts made in Hudson's River above the City, but they effected nothing. One of them was by the aforementioned person. In going toward the Ship, he lost sight of her, and went a great distance beyond her, before he found her; when he arrived, the tide ran so strong, that as he descended under water, for the Ship's bottom, it swept him away. Soon after this, the Enemy went up the river, and pursued the boat, which had the submarine Vessel on board, and sunk it, with their shot. After I recovered the Vessel, I found it impossible, at that time to prosecute the design any farther. I had been in a bad state of health from the beginning of my undertaking, and was now very unwell; the situation of public affairs was such, that I despaired of obtaining the public attention, and the assistance necessary. I was unable to support myself, and the persons I must have employed, had I proceeded. Beside I found it absolutely necessary, that the operators should, acquire more skill in the management of the Vessel, before I could expect success; which would have taken up sometime, and made no small additional expence. I therefore gave over the pursuit, for that time, and waited for a more favourable opportunity, which never arrived.
Other Experiments made with a design to fire Shipping.
In the year 1777, I made an attempt; from a Whaleboat, against the Cerberus Frigate, then lying at anchor, between Connecticut River & New London, by drawing a Machine against her side, by means of a line. The Machine was loaded with Powder, to be exploded by a gunlock, which was to be unpinioned by an apparatus, to be turned by being brought along the side of the Frigate. This Machine fell in with a schooner, at anchor astern of the Frigate, & concealed from my sight. By some means or other it was fired, and demolished the schooner, and three men, and blew the only one left alive, overboard, who was taken up very much hurt.
After this, I fixed several Keggs under water, charged with powder, to explode upon touching anything, as they floated along with the tide: I set them afloat in the Delaware, above the English shipping at Philadelphia, in December 1777. I was unacquainted with the River, and obliged to depend upon a Gentleman, very imperfectly acquainted with that part of it, as I afterwards found. We went as near the shipping as he durst venture; I believe the darkness of the night greatly deceived him, as it did me. We set them adrift, to fall with the ebb upon the Shipping. Had we been within sixty rods, I believe they must have fallen in with them immediately as I designed; but, as I afterwards found, they were set adrift much too far distant, and did not arrive, until after being detained some time by frost, they advanced in the day time in a dispersed situation, and under great disadvantage. One of them blew up a boat, with several persons in it, who imprudently handled it too freely, and thus gave the British that alarm, which brought on the battle of the Keggs. David Bushnell
Source: The enclosures contained in Bushnell's letter to Thomas Jefferson are not included with the letter in the Jefferson Papers, Library of Congress, Washington, DC. Bushnell's description of the submarine and "Other Experiments" was published in Transactions of the American Philosophical Society, Philadelphia, 1799.
(12) Ezra Lee to David Humphreys
|Lyme 20th Feby 1815.|
Judge Griswold, & Charles Griswold Esq. both informed me that you wished to have an account of a machine invented by David Bushnell of Say. Brook, at the commencement of our Revolutionary war. In the summer of 1776, he went to New York with it to try the Asia man of war: - his brother being acquainted with the working of the machine, was to try the first experiment with it, but having spent untill the middle of August, he gave out, in consequence of indisposition. - Mr. Bushnell then came to General Parsons (of Lyme) to get some one to go, and learn the ways & mystery of this new machine, and to make a trial of it.
General Parsons, sent for me, & two others, who had given in our names to go in a fire ship if wanted, to see if we would undertake the enterprize: - we agreed to it, but first returned with the machine down Sound, and on our way practised with it in several harbours. - we returned as far back as Say-Brook with Mr Bushnell, where some little alterations were made in it - in the course of which time, (it being 8 or 10 days) the British had got possession of Long Island & Governor's Island - We went back as far as New Rochelle and had it carted over by land to the North River. -
Before I proceed further, I will endeavour to give you some idea of the construction of this machine, turtle or torpedo, as it has since been called. - (1) Its shape was most like a round clam, but longer, and set up on its square side - it was high enough to stand in or sit as you had occasion, with a (2) composition head hanging on hinges. - it had six glasses, inserted in the head, and made water tight, each the size of a half Dollar piece, to admit light - in a clear day, a person might see to read in three fathoms of water - The machine was steered by a rudder having a crooked tiller, which led in by your side, through a water joint. - (3) then sitting on the seat, the navigator rows with one hand, & steers with the other - it had two oars, of about 12 inches in leangth, & 4 or 5 in width, shaped like the arms of a windmill, which led also inside through water joints, in front of the person steering, and were worked by means of a wench (or crank) and with hard labour, the machine might be impelled at the rate of 3 nots an hour for a short time - Seven hundred pounds of lead were fixed on the bottom for ballast, and two hundred weight of it was so contrived, as to let it go in case the pumps choaked, so that you could rise at the surface of the water. - It was sunk by letting in water by a spring near the bottom, by placing your foot against which, the water would rush in and when sinking take off your foot & it would cease to come in & you would sink no further, but if you had sunk too far, pump out water untill you got the necessary depth - these pumps forced the water out at the bottom, one being on each side of you as you rowed - A pocket compass was fixed in the side, with a piece of light (4) wood on the north side, thus +, and another on the east side thus -, to steer by while under water - Three round doors were cut in the head, (each 3 inches diameter) to let in fresh air, untill you wished to sink, and then they were shut down & fastened - There was also a glass tube (5) 12 inches long and 1 inch diamater, with a cork in it, with a peice of light wood, fixed to it, and another peice at the bottom of the tube, to tell the depth of discent, - one inch rise of the cork in the tube gave about one fathom water, - It had a screw, that peirced through the top of the machine, with a water joint, which was so very sharp that it would enter wood, with very little force, and this was turned with a wench, or crank, and when entered fast in the bottom of the ship, the screw is then left, and the machine is disengaged, by unscrewing another one inside that held the other. From the screw now fixed on the bottom of the ship, a line - led to & fastened to the mazagine, to prevent its escape either side of the ship - the magazine was directly behind you on the outside, and that was faced from you by unscrewing a screw inside - Inside the magazine was a clock machinery, which immediately sets a going after it is disengaged & a gun lock is fixed to strike fire to the powder, at the set time after the Clock should rundown - The clock might be set to go longer or shorter - 20 or 30 minutes was the usual time, to let the navigator escape - This magazine was shaped like an egg, & made of oak dug out in two peices, bound together with bands of iron, corked & paid over with tar so as to be perfectly tight, and the clock was bound so as not to run untill this magazine was unscrewed .....
I will now endeavour to give you a short account of my voyage in this machine. - The first night after we got down to New York with it, that was favourable, (for the time for a trial, must be, when it is slack water, & calm, as it is unmanagable in a swell or a strong tide) the British Fleet lay a little above Staten Island We set off from the City - the Whale boats towed me as nigh the ships, as they dared to go, and then cast me off - I soon found that it was too early in the tide, as it carried me down by the ships - I however hove about, and rowed for 5 glasses, by the ships' bells, before the tide slacked so that I, could get along side of the man of war, which lay above the transports - The Moon was about 2 hours high, and the daylight about one - when I rowed under the stern of the ship, could see the men on deck, & hear them talk - I then shut down all the doors, sunk down, and came under the bottom of the ship, up with the screw against the bottom but found that it would not enter - (6) I pulled along to try another place, but deviated a little one side, and immediately rode with great velocity, and come above the surface 2 or 3 feet between the ship and the daylight - then sunk again like a porpoise I hove partly about to try again, but on further thought I gave out, knowing that as soon as it was light the ships boats would be rowing in all directions, and I thought the best generalship, was to retreat, as fast as I could as I had 4 miles to go, before passing Governor's Island. - So I jogg'd on as fast as I could, and my compass being then of no use to me, I was obliged to rise up every few minutes to see that I sailed in the right direction, and for this purpose keeping the machine on the surface of the water, and the doors open - I was much afraid of getting aground on the island as the Tide of the flood set on the north point While on my passage up to the City, my course owing to the above circumstances, was very crooked & zig zag, and the enemy's attention was drawn towards me, from Governors Island - When I was abreast of the fort on the island 3 or 400 men got upon the parapet to observe me, - at leangth a number came down to the shore, shoved off a 12 oar'd barge, with 5 or 6 sitters, and pulled for me - I eyed them, and when they had got within 50 or 60 yards of me, I let loose the magazine, in hopes, that if they should take me, they would likewise pick up the magazine, and then we should all be blown up together, but as kind Providence would have it, they took fright, and returned to the island, to my infinite joy. - I then weathered the Island, and our people seeing me, came off with a whaleboat, and towed me in - The Magazine after getting a little past the Island, went off with a tremendous explosion, throwing up large bodies of water to an immense height. (7)
Before we had another opportunity to try an experiment our army evacuated Newyork, and we retreated up the North River as far as fort Lee - A Frigate came up and anchored off Bloomingdale. I now made another attempt upon a new plan - my intention was to have gone under the ship's stern, and screwed on the magazine close to the water's edge, but I was discovered by the Watch and was obliged to abondon this scheme, then shutting my doors, I dove under her, but my cork in the tube, (by which I ascertained my depth) got obstructed, and deceived me, and I descended too deep & did not track the ship, and I then left her - Soon after the Frigate came up the river, drove our Crane galley on shore, and sunk our Sloop, from which we escaped to the shore -
I am &c. E. Lee.
For General David Humphreys -
(1) This machine was built of oak, in the strongest manner possible, corked and tarred, and though its sides were at least six inches thick, the writer of the forgoing, told me that the pressure of the water, against it, at the depth of two fathoms was so great, that it oozed quite through, as mercury will by means of the air pump. Mr. Bushnell's machine was no larger than just to admit one person to navigate: - its extreme leangth was not more than 7. feet. - When lying in the water, in its ordinary state without ballasts, its upper works did not rise more than 6 or 7 inches out of water -
(2) This composition head, means of composition of Metals - something like bell metal, and was fixed on the top of the machine, and which afforded the only admission to the inside -
(3) The steering of this machine was done on the same principles, with ordinary vessels, but the rowing her through the water, was on a very different plan - These oars, were fixed on the end of a shaft like windmill arms, projected out, forward, and turned at right angles with the course of the machine, and upon the same principles that windmill arms are turned, by the wind these oars, when put in motion as the writer describes, draws the machine slowly after it - this moving power is small, and every attendant circumstance, must cooperate with it, to answer the purpose, calm waters & no current -
(4) This light wood is what we sometimes call fox fire, and is the dry wood that shines in the dark: - this was necessary as the points of the compass could not readily be seen without -
(5) The glass tube here mentioned, which was a sort of thermometer, to ascertain the depth of water the machine descended, is the only part that is without explanation - the writer of the forgoing, could not reccollect the principles on which such an effect, was produced, nor the mechanical contrivance of it - He only knows that it was so contrived that the cork & light wood rose or fell in the tubes, by the ascent or descent of the machine -
(6) The reason why the screw would not enter, was that the ship's bottom being coppered it would have been difficult under any circumstances to have peirced through it - but on attempting to bore with the auger, the force necessary to be used in pressing against the ships bottom, caused the machine to rebound off this difficulty defeated the whole. - the screw could not enter the bottom, and of course the magazine could not be kept there in the mode desired -
(7) When the explosion took place, General Putnam was vastly pleased, and cried out in his piculiar way - "God's curse 'em, that'll do it for 'em." 1
1 These explanatory notes were apparently added by Humphreys.
Source: Yale University Library. A slightly modified version of the letter was published in The Magazine of American History, vol. 29 (January-June 1893).