HAYES— U. S. NAVY MV TYPE OF HYDROPHONE. 399 



U. S. S. Breckinridge, Sounding Data Over Jagged, Uneven 



Sea-Bottom. 



During the month of January, 1920, while making a trip from 

 Charleston to Key West on board the U. S. Destroyer Breckinridge, 

 the writer had an opportunity of testing the utility of the MV hydro- 

 phone for sounding purposes under very adverse conditions. The 

 Breckinridge had been fitted with an electrical MV hydrophone, the 

 lines of which were installed in tanks built in the bottom of the 

 vessel near the bow. The tests were made over a period of 10 

 hours while the Breckinridge was proceeding down the coast on a 

 course which ran in part along the edge of the continental shelf, so 

 that the bottom was very uneven and erratic, and pronounced 

 changes in depth occurred. Two successive casts of the hand-lead, 

 made not more than one minute apart and taken with the vessel 

 moving less than five knots, frequently showed a discrepancy of 

 from 5 to 6 fathoms. 



At half-hour intervals soundings were made both by hand-lead 

 and the automatic sounding machine, the vessel of necessity being 

 slowed to about 3 knots for these operations. Just before stopping 

 and after starting the propellers soundings were taken upon the 



