Captain Richard Webb, Director of Trade Division, British Admiralty, Memorandum to Rear Admiral William S. Sims
MEMORANDUM TO SHIPPING INTELLIGENCE OFFICERS
15th. April 1917.
Herewith is forwarded for your information copy of telegram which has been sent to all Intelligence Centres in the Atlantic on the subject of zig-zagging and extinction of lights.
As regards (I) it will be seen that the area for zig-zagging has been considerably extended beyond that already laid down, and this new area is to be brought into force for outgoing vessels also.
Your attention is also called to the fact that all references to zig-zagging during moonlight only have been omitted, and it is now laid down that vessels are to zig-zag during day and night. This is considered necessary owing to the fact that several vessels hhave recently been torpedoed during dark moonless nights while not zig-zagging, and this inspite of the fact that they were not showing navigation lights. It must be remembered, however, that zigzagging should not be carried out when following a buoyed or swept channel, but it was not considered necessary to overload the telegram by mentioning this fact which can be communicated to vessels on their arrival at home ports.
As regards (2) it is recognized that in ships with only a single Operator, it is practically impossible to keep a constant wireless watch owing to the great strain it imposes on the Operator, and it is unfortunately the case that sufficient Operators are not forthcoming at present to provide two for ach vessels.
At the same time it must be borne in mind by Masters that the more constant the watch, the more probability there is of picking up signals made at times other than those laid down for War Warnings &c., and this is particularly the case with S.O.S. messages sent out by vessels attacked by submarines.
As regards (3) this practically in line with the orders now in force, and the reference at (a) is intended primarily to cover such occasions as those in which vessels proceeding up and down the English Channel have under present regulations to show lights at various points.
As regards (4) the attention of the Admiralty has been called to the fact that confusion still exists owing to the bearings and courses sometimes being signaled true and a sometimes magnetic. Magnetic is always to be the rule in future.
As regards (5) the general principles of zig-zagging may always be explained to Masters of Neutral vessels who show any desire to do so, and the importance of zig-zagging should be impressed on such Masters.
Source Note: TD, DNA, RG 45, Entry 520. The recipient is not given but given that this copy was in American archives and given that Webb wrote he was forwarding it “for your information,” the editors surmise that he sent it to Sims. In the upper right-hand corner of this document is the identifier “A – 15 April-/Confi file/3/J.”