Lieutenant Commander Archibald McGlasson to Rear Admiral Henry B. Wilson, Commander, United States Naval Forces in France
U.S.S. John B. Hinton
November 4th, 1917.
From: Commanding Officer,
To: Commander, Patrol Squadrons,
Subject: Report on “C” Tube Experiments.
1. Left Brest on afternoon of November 2nd accompanied by trawlers Douglas, Courtney, James and Lewes and the French Submarine Germinal, and proceeded to Baie de Douarnenez.1 Four of the trawlers, Douglas, Courtney, James and Lewes were anchored in the northern part of the Bay off Pt. Morgat, distance about 500 yards apart at 7.30 P.M. The submarine steamed on an East and West course back and forth across the Bay testing radio with Ushant radio station at a speed of from 5 to 7 knots, running on surface followed by the U.S.S. Hinton. At all times during the three days of exercises, the submarine was convoyed by the Hinton at a distance of from 200 to 500 yards to prevent French fishermen from firing on the submarine. The submarine held these radio tests until 11.30 P.M. when she headed for the anchorage where the trawlers were anchored, thus simulating an attack and later anchored. The weather was clear and sea was calm during these tests. During this time the anchored trawlers listened in with the “C” Tubes and were able to hear the submarine propellers at a distance of 2000 yards (intensity of sound, loud) and faintly as a distances of 4000 yards; the sound of the Hinton’s propellers could easily be distinguished from the sound of the submarine’s propellers.
2. On November 3rd, underway at 7:00 A.M., the submarine commenced an eight hour run submerged, speed 5 knots to 7 knots, periscope showing about a foot or two. Submarine steamed back and forth across the bay on an East and West course closely followed by the Hinton. Two trawlers operated in south side of the Bay and two in the north side of the Bay listening in with “C” Tubes at anchor and drifting. Distances were accurately obtained by using sextant angle on Hinton’s mast. Weather during morning was foggy and rainy, sea smooth. Weather during the afternoon was clear, sea small swell. The submarine could be heard varying distances by the four ships, one ship could hear it faintly at 5000 yards and 6000 yards and other ships at 4000 yards. Direction of submarine could be ascertained within 10 degrees. Gun crews on the Hinton were exercised at pointing at periscope. The periscope could ordinarily be detected by the naked eye at a distance of 1000 yards and over that up to 1500 yards, when general direction of submarine was known.
3. On the night of November 3rd, the submarine ran on surface same course, and same speed, carrying on radio tests. The Douglas was detailed to convoy the submarine, other ships anchored. Owing to darkness setting in the submarine was lost sight of before the Douglas could take up a position astern of her and “C” tubes were used to locate submarine; direction was located after taking three observations and after ten minutes steaming (approximate distance 2500 yards), the submarine was sighted dead ahead. All ships anchored listened in with “C” tubes at intervals of ten minutes commencing at 9.30 P.M. The submarine and Douglas could be heard at distances up to 3000 yards (sea smooth) sound of Douglas’ propellers (slow humthrob) could be distinguished from sound of the submarine’s propellers (low hum) and when either stopped or slowed down at turns it could be detected by “C” tubes. When submarine headed for anchorage at 11.30 P.M. it was easily detected by tubes faintly at a distance of 3500 yards on Hinton and loudly at a distance of 2000 yards, and from the direction of the sound it could be judged that the submarine was heading for the anchorage.
4. On morning of November 4th, the submarine submerged (periscope showing) for a period of one hour, all ships exercised with tubes but submarine barely moved in the water and exercises were of little value. At 9:00 A.M. submarine came to surface and all ships proceeded to Brest.
a. The results obtained were very favorable; accurate distances were obtained up to 5000 yards and directions to within 10 degrees.
b. The best results were obtained when submarine was from one or two degrees forward of the beam to one or two degrees aft of the beam. When anchored near shore the surf interfered with operation of tubes. Best results were obtained when ship was drifting with auxiliary machinery stopped. Rain interfered with operation of tubes but this can be overcome by placing canvas screens over operators. When anchored waves seemed to interfere slightly, making a gurgling sound in tube. When steaming 8 or 9 knots it required at least 3 minutes to bring ship to a dead stop, get “C” tubes over and obtain approximate direction of submarine; on Hinton the auxiliary machinery did not interfere greatly with the operation of the tubes, but results were better when auxiliary machinery was stopped. When listening in any length of time (over an hour) better results can be obtained by listening in at intervals of 5 or 10 minutes and changing the operators; continuous listening in is very tiring on the ears and one case was noted where it caused an operator’s ear to bleed.2
Source Note: TLS, DNA, RG 45, Entry 520, Box 339.
Footnote 1: Baie de Douarnenez is south of Brest on the West Coast of France.
Footnote 2: For more on “C” tube listening devices and the emergence of early sonar, see: Frank Schofield Memorandum of 13 October 1917.