12 Prof. J. Joly on Scientific 



mechanism of the submarine bell was tripped and a stroke 

 was given to the bell. The coincidence of all three signals 

 was tested by observation close to the lightship. 



On board the U.S.S. ' Washington 3 the interval between 

 the arrival of the aerial sounds and the wireless tick was read 

 and recorded to one half second ; and that between the bell- 

 stroke and the wireless to tenths of seconds. It was assumed 

 that the velocity of sound in air at the prevailing temperature 

 (6<5 o, F.) was 1132 feet per second, and in water (at 66° F.) 

 4794 feet per second. The weather was calm and hazy. 



The course steered was first due West from the lightship 

 for a distance of 8 miles, then turning and heading E.S.E., 

 the lightship being passed on the port beam at a distance of 

 43450 yards. Standing on for 8 miles further she turned to 

 the N.W., passing the lightship on the port beam at about 

 4600 yards ; and thence back to the lightship on a S.E. 

 course. 



At starting the whistle and bell were right astern. The 

 bell was lost at a distance of about 2 miles, and the whistle 

 at, it is stated, about halt" a mile. The loss of the sound of 

 the whistle can only be ascribed to the phenomenon of silent 

 areas. The loss of the bell is a consequence of the defective 

 presentation of the receiving tanks towards sounds coming 

 from right astern. As might be expected, the bell was not 

 again picked up till the ' Washington' turned to go eastward. 

 It was then picked up at a distance of about 7*6 miles, the 

 lag of the sounds on the radio dots being 9*5 seconds. The 

 sounds were then reaching her on the port bow. The whistle 

 was not recovered till the 4 Washington ' had approached much 

 nearer to the lightship — a distance of about 4 miles. Bell 

 and whistle were held on this course till the lightship was 

 passed and left well astern, the bell sound being lost when 

 the distance from the lightship was about 5J miles, and the 

 angle of approach of the sounds was 19° with the course and 

 approaching on the stern of the 'Washington/ This, again, is 

 to be expected as a consequence of the lessening presentation 

 of the receiving tanks. The whistle was held on this E.S.E. 

 course till the ' Washington' was about 1\ miles from the 

 lightship. Here the whistle had the advantage. The bell 

 was recovered immediately on turning N.W., and when the 

 distance was 8*6 miles. The whistle was picked up on the 

 N.W. course when 6 miles from the lightship. The real 

 superiority of the submarine transmission of sound is here 

 plainly shown. Both sounds ay ere then held till the 

 finish. 



The course of the ship and each observation are recorded 



