360 NEWTON S PRINCIPIA. 



By experiment, the value of the left hand side could be 

 found, and therefore, by the solution of an equation, that of 

 x. In making these experiments, the necessary corrections 

 to /, 8, &c. due to heat and other causes must not be for 

 gotten. It is not our office at present to consider these. 

 If N be the number of oscillations made in air as cal- 



N N 

 culated on the old theory, then the value of ^ may be 



found from the above by writing x = 0. And thence the 



N&quot;-- N 

 value of -r- - the number of times the old correction 



must be multiplied to get the new. This ratio we shall 

 call n. By regarding 8 as small, and expanding, we get 



Now usually y is very nearly equal to /, and -= is very small ; 



hence 



N&quot; N l 



. &quot;IT- = ( +*) 8 l near , y . 

 n = 1 -f x J 



This is the method that has been adopted by Sabine and 

 Baily. Their memoirs will be found in the Phil. Trans, 

 for 1829 and 1832. The former experimented chiefly on 

 the effects of different media and of changes in the ex 

 ternal circumstances; the latter on the different resistances 

 experienced by different forms of bodies. 



Coulomb, in his experiments, adopted a different me 

 thod ; he made a small plane perform small oscillations in 



