make-it-happen naval officer. The following day, Mitchell and Ryan installed operational indicator loops in the channel, possibly working from Ryan’s new facility at Hawkcraig Point. Over the next few weeks, Mitchell monitored the galvanometer, recording the comings and goings of the naval squadron based at Rosyth. His overwhelming success was reported to the Royal Society, which had funded the work, the results soon forwarded to the Admiralty Board of Invention and Research.14
The response of the BIR, whose mission included reviewing ideas submitted by British citizens, was not at all encouraging. The report was probably given only a cursory review, as it was only one of thousands of suggestions being submitted to the BIR. The decision makers who reviewed these suggestions, including Professor Mitchell’s report, often relied on estimates by scientists at the National Physics Lab in London who had already discounted the viability of electromagnetics as a method of submarine detection. One member of the BIR, physicist William Henry Bragg, began to reconsider Mitchell’s experimental results, and, although it wasn’t until November, 1916, renewed the effort to develop the loop idea. During the following year, indicator loop experiments conducted at the Parkeston Quay Experimental Station at Harwich led to operational “Bragg Loop” submarine detection systems being deployed at shore stations during 1918. That same year, a similar indicator loop technology was developed in the U.S. at the Naval Experimental Station and installed at the entrance to Chesapeake Bay.15
The war was almost over when a U-boat made an attempt to attack the British Grand Fleet, thought to be at anchor in Scapa Flow. Unfortunately for the U-boat, the fleet had left the Orkneys—but the Stanger Head hydrophone station at the entrance to Scapa Flow was still operating. To make entry even more perilous, a dozen Bragg indicator loops had been installed along the mine barrage. While the well-trained petty officers with their headphones listened intently for the distinctive sounds of a transiting U-boat, another member of the shore station crew kept watch on the dozen galvanometers, each with a known location near specific groups of mines. The listener tracked the approximate location and direction of the submarine based on the intensity of the sound from each of the line of five bottom-mounted hydrophones. As the invader approached and crossed one of the indicator loops, a member of the six-man crew, with his finger on the button, was ready to detonate the nearest mines.16
UB 116 … set off with a volunteer crew of officers, bent on a gallant attempt to penetrate into Scapa Flow and there sink the British flagship. The forlorn venture was sadly misdirected, since the Grand Fleet was at that time in the Firth of Forth. On October 28 [1918], the submarine was located on the screen connected with electrical detectors of the outer Hoxa defenses [at the entrance to Scapa Flow]. When she was well over the field of controlled mines, the circuit was closed.17
The Scottish family who provided the funds to the Royal Society of Edinburgh which led to the development of “electrical detectors,” later losing two sons in the war, may have gained some satisfaction if they learned these systems had contributed to the sinking of at least one U-boat. While the technology—hydrophones and magnetic loops—in the hands of the naval personnel who manned the listening posts had to be operating at peak efficiency, so did the sailors. For them, success against Germany’s “Raiders of the Deep” depended on training, not luck.
CHAPTER 5 A GAME OF HIDE AND SEEK
[V]essels were formed into special hydrophone flotillas, whose duties consisted of listening in long lines for submarines and when a discovery was made attacking them in the most approved tactical formation, with the aid of depth charges … Nearly all U-boats were fitted with a number of hydrophones and therefore were as well able to receive timely warning of an approaching surface ship as the surface ship was of the presence of the submarine … [allowing] a game of hide and seek to be played between a hunting vessel and a hunted submarine.
—Charles Domville-Fife, Submarine Warfare of Today, 1920.1
In his 1920 book Submarine Warfare of To-Day, Charles Domville-Fife related his experiences as commander of a British hydrophone flotilla engaged in antisubmarine operations. German submarines had enjoyed the ability to disappear beneath the sea after an attack on an unarmed merchant ship, becoming nearly undetectable once they submerged. It would be more than a year before the Royal Navy would have a vessel designed specifically for submarine hunting—fast, maneuverable, and capable of operating far off shore. Success as an antisubmarine asset, however, was dependent on the hydrophone and the listeners on board.
During the first two years of the war, as Commander Ryan, who had been promoted to Captain, continued to develop hydrophones for shore-based listening posts, the only vessels available in any significant numbers for submarine patrols around the British Isles were commercial trawlers and what were referred to as “drifters” because of the drift nets used for fishing. Once commissioned, the vessels’ crews became members of the Royal Navy Reserves (RNR) or the Royal Navy Volunteer Reserves (RNVR). The trawlers and drifters, according to Domville-Fife, each numbering well over one thousand, were initially employed in minesweeping and coastal patrols. The ships carried armament in the event they encountered a surfaced U-boat, but were often out-gunned by the submarine. “[Trawler] losses were heavy, both in ships and men, amounting to about 30 per cent,” as indicated by Domville-Fife, while drifter “losses amounted to about 20 per cent.”2
Domville-Fife quoted an article in an American magazine, Rudder, written by Henry R. Sutphin, vice president at Electric Boat Company and manager of Electric Launch Company (Elco), one of the businesses purchased by Electric Boat in 1899.
It was February, 1915, that we had our initial negotiations with the British Naval authorities. A well-known English ship builder and ordnance expert [Sir Trevor Dawson] was in this country, presumably on secret business for the Admiralty, and I met him one afternoon at his hotel…. I suggested the use of a number of small, speedy gasoline boats for use in attacking and destroying submarines. My idea was to have a mosquito fleet big enough to thoroughly patrol the coastal waters of Great Britain, each of them carrying a 13-lb. rapid-fire gun.3
Sutphin was asked how many of the 80-foot vessels could be delivered within a year. “I told him I could guarantee fifty.” A short time later, Sutphin was informed that the British Government was interested, and on the 9th of April, a contract for fifty of these “chasers” was signed. A month later, however, the submarine U-20 torpedoed and sank the Cu-nard Liner Lusitania. According to Domville-Fife, Sutphin’s British contact asked him if a larger order could be managed; Sutphin’s response: “I told him that I could guarantee to build a boat a day for so long as the Admiralty might care to name.” The Admiralty’s reply was soon forthcoming, and a contract for an additional five hundred “Chasers” was signed on the 9th of July.4
The Admiralty designated these as Motor Launch (ML) class vessels, with a desired speed of nineteen knots. The speed was simple arithmetic. A submerged U-boat may have been capable of as much as ten knots, although most were limited to about six to eight knots. A submarine on the surface, however, could run at nearly seventeen knots, eluding most of the patrol craft available to the Admiralty.5 Pursuit by a destroyer, however, was a different matter. With speeds over thirty knots, a U-boat risked ramming if spotted on the surface, or if, having fired a torpedo, the destroyer could follow the track of the torpedo back to the submarine.
The USS Aylwin (DD-47) represents the type of destroyer used by American and British forces in the war zone. (NHHC NH 77908) Before the development of effective listening devices, destroyers would follow the track of a torpedo
in an attempt to ram the U-boat. (Sims, 1919-1920)
