Letter from WSC, First Lord of the Admiralty to the Commander-in-Chief, Grand Fleet [Admiral Sir John Jellicoe], on the proposed capture of the island of "Sylt" [Borkum, Germany] for use as a submarine base, and on the value of submarines as a deterrent against German warships. [Typescript copy; fuller original version at CHAR 13/46/14, and fuller typescript version at CHAR 13/46/32-36.].