32 



PENDULUMS. 



SOLUTION. 50 : 6.25 (the sq. root of 39.1013):: 60 : Y.5, 

 then 7.5 2 =56.25 inches. Ans. 



To find the number of vibrations per minute , the length 

 of the pendulum being given. 



RULE. As the square root of the length of the pendu- 

 lum is to 60, so is the square root of 39.1013 to the number 

 of vibrations required. 



EXAMPLE. How many vibrations will a pendulum 64 

 inches long make in a minute ? 



SOLUTION. 8 (square root of 64) : 60:: 6.25 (sq. root of 

 39.1013) : 46.875 vibrations. Ans. 



TABLE showing the planets, comparative size, dec., in the 

 solar system. 



