Captain Richard H. Jackson, United States Naval Attaché in Paris and United States Naval Staff Representative, to Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters
July 16, 1918
Source, Naval Attache, Paris Copies to C S
C S 2
Subject Listening apparatus. P 1
Experiments made with the Walser listening apparatus by the French Gunboat ENGAGEANT and submarine AMARANTE have convinced the Commission that all gunboats should be equipped with this device as quickly as possible.
Under very favorable conditions the ENGAGEANT was able to hear the submarine for a distance of 4100 meters. Sonorous contact was lost at 5000 meters.
Commander of MOUETTE 11, escorting convoy to Messina-Corfu, and Palermo three times attackes [i.e., attacked] by submarine unsuccessfully attributes his success to the Walser apparatus.
Source Note: Cy, DNA, RG 45, Entry 520, Box 337.