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



the base-line (2L) of the vessel Accurate hydrophone soundings 

 could be made at all times and these, as will be shown, were a very 

 great aid in navigating. 



During the first day's run from New London to Provincetown 

 through the Cape Cod Canal, the weather was clear so that a close 

 check upon the progress of the vessel could be kept by observation 

 of beacons along the shore. Hydrophone soundings were made 

 from time to time and these were seen to agree closely with the 

 depths given on the chart, thus affording a check upon the computed 

 scale. The same procedure was carried out during the second day 

 when the trip was made across Massachusetts Bay to the port of 

 Salem. 



Departure from Salem was made in a heavy fog. After clearing 

 Cape Anne a compass course was set for Boon Island, off the coast 

 of York, Maine. This small island is rather peculiar hydrograph- 

 ically in that it consists of a small peak rising abruptly in a sea of 

 fairly deep water. A continuous sounding watch was maintained 

 until the hydrophone suddenly showed a very rapid shoaling of the 

 water in the position marked (i). Warning was given just in time 

 to enable the navigator to make out a buoy off the island which was 

 passed at close range. Had it not been for these hydrophone sound- 

 ings the locating of this small island would have been a more tedious 

 and hazardous project in the thick weather prevailing. A course 

 was then set for the Portland lightship; soundings were taken en 

 route to check the progress of the submarine. The submarine bell 

 on this lightship was picked up and located at position (2), some- 

 thing over a mile before reaching it. Further aid was also afforded 

 by the hydrophone while passing Cape Elizabeth and entering the 

 harbor. 



The submarine left Portland two days later in a settled spell of 

 thick weather. Taking a departure from the lightship a course was 

 laid almost wholly by compass and hydrophone soundings. At many 

 points along this route, such as are indicated by (4) and (5), sudden 

 changes in the depth of water were very readily noted and afforded 

 excellent checks upon the progress being made by the vessel — in this 

 manner serving the purpose of the log. The shoaling water off the 



