Chap. 3'.") in a Siphon and in Waves. 467 



Jogous to the ofcillatory motion of water in a fiphon, 

 and they obferve the fame Jaws relative to their du- 

 ration. 



If there is then a pendulum, the length of which is 

 equal to half the tranfverfal diltance that exifts between 

 the top or apex of a wave A (for example) and the 

 cavity B, that is equal to half A, the higheft parts 

 will become the loweft in the fame fpace of time in 

 which this pendulum vibrates, and in the fpace of 

 another ofcillation they will again become the higheft. 

 Each of thefe waves then will roll its whole courfe 

 during the time which the pendulum takes in perform- 

 ing two ofcillations ; and as a pendulum four times the 

 length of the preceding, that is, the length of,which is 

 equal to the width of the wave A C 3 will make only one 

 - ofcillation, while the firft makes two, it follows, that 

 the waves perform their ofcillations in the fame fpace of 

 time as a pendulum equal in length to the width of 

 the fame waves would perform its ofcillations. What 

 is meant by the width of waves, is the tranfverfal fpsce 

 A C, which is between their greateft elevations, or 

 the fpace B D, which is between their greateft conca- 

 vities. 



It follows from thefe premifes, that waves, which 

 are about three feet and three quarters of an inch wide, 

 roll their whole width during a fecond of time, and 

 confequently they roll one hundred and eighty-three feet 

 fix inches and five-fixths in a minute, and in an hour 

 eleven thoufand and fourteen feet two inches j waves 

 four times as wide will roll this fpace in twice the 

 time j it follows then, that the wider or more ex- 

 panded the waves are, the greater will be the fpace 

 which they roll over in a given time. 



But what has now been ftated refpe&ing the motion 

 H h 2 of 



