184 Transactions. — Miscellaneous. 



from E and F simultaneously. If by means of the screw S 

 the lever C D was depressed below A B, the falling weight 

 reached the lever AB first, and after a certain definite interval 

 the lever C D. 



The interval of time was calculated as follows : — 



Fig? 



CM E 



Let A B, CD be the two levers when horizontal. Let 

 the screw be given ii turns, so that the lever C D is then in 

 the position C D. Let E and E' be the ends of the screw in 

 the two positions. Let be the angle C D C. Let li = height 

 of weight above the first lever. The velocity with which the 

 weight reaches the lever A B is given by y^gh, assuming the 

 body falls freely under the influence of gravity. As the dis- 

 tance between the levers was never greater than Mn., and h 

 was generally 3ft., we may assume the velocity to be sensibly 

 constant over the interval. 



Let il = distance between threads of screw : 



Then E E' = nd. 



Let C D = Z ; E D = /j ; let C M be vertical distance be- 

 tween the two levers : 



C M = C D sin. 6 



nd 



= . nd 1 - 1, „ -f- etc. 



Now, nd in these experiments was never more than |-in., 

 and ^1 = 4:-81in. The value of the correction due to C moving 

 over the arc of a circle may therefore be neglected. 



The time taken to move over the vertical distance C M, 

 assuming velocity constant, is given by 



ndl 



In the actual experiments 



d = Jjjin. ; 



I = 6-125in. ; 



I, = 4-81in. ; 



h = 3ft. ; 

 .-. t = n X 0-000192 nearly. 



.'. the time to cross over an interval corresponding to one 

 turn of the screw is 0-000192 seconds. The screw-head was 



