VOL. II.] PHILOSOPHICAL TRANSACTIONS. 156 



fathoms measured by the Hne, the globe stay under water 15 seconds; then if 

 the ball stay 700 seconds, the depth of the sea is 933 fathoms and two feet, if 

 the ball be found to move equal spaces in equal time. 



In the same trials made with this instrument in the Thames, it has been 

 found that there was no difference in time between the submersions of the ball 

 at the greatest depth, when it rose several yards from the place where it was let 

 fall, being carried by the current of the tide, and when it rose only a yard or 

 so from the same place where it was let down. 



And if it be alleged that it must be known, when a light body ascends from 

 the bottom of the water to the top, in what proportion of time it rises ; it may 

 be considered that in this experiment the times of the descent and ascent are 

 both taken and computed together; so that for this purpose there needs not the 

 nicety which is alleged. 



Of other experiments of this way of sounding without a line, made by the 

 noble Lord Viscount Brounker, Sir Robert Moray, Knight, and Mr. Hook, in 

 the channel at Sheerness, the following account was given, viz. 



Weighed Oz. Gr. 



A wooden ball (A) 32^ O 



Another wooden ball (B) .30 22 



A lead (A) 30 O 



Another lead (B) 30^ O 



The ball (B) and the lead (B) were let down at l6 fathoms; and the ball 

 returned in 48 single strokes of a pendulum, held in the hand, vibrating 58 

 single strokes in a minute. 



A second time repeated with the same success ; therefore the motion was four 

 feet every second. 



Again the ball (A) and the lead (B), the nail of which was bent into a sharper 

 angle, the ball returned in 39 strokes. A second time repeated with the same 

 success, at the same depth. 



Ball (B), lead (B), in which trial the line, not being clear, stopped a little the 

 motion, the ball returned in 47 at the same depth. 



Ball (A) lead (A) at eight fathoms and one foot, returned at 20. 



Repeated at eight fathoms, returned at 19. 



Tried the third time at ten fathoms and four feet, returned at 28. 



A fourth trial, at the same depth, just the same. 



A fifth at ten fathoms five feet, returned in 27. 



A sixth trial, just the same. 



A seventh at twelve fathoms five feet, in 37. 



An eighth trial, just the same. 



U 2 



