OF NATURAL PHILOSOPHY. 24-7 



and the same is true, even in a greater degree, in 

 liquids and solids ; for in these the elastic forces 

 are even greater, in proportion to the weight, than 

 in air. 



(270.) A general notion of the mode in which 

 sounds are conveyed through the air was not alto- 

 gether deficient among the ancients; but it is to 

 Newton that we owe the first attempt to analyze 

 the process, and show correctly what takes place in 

 the communication of motion from particle to par- 

 ticle. Reasoning on the properties of the air as an 

 elastic body, he showed the effect of an impulse on 

 any portion of it to consist in a condensation of 

 the air immediately adjacent in the direction of the 

 impulse, which then, re-acting by its spring, drives 

 back the portion which had advanced to its original 

 place, and at the same time urges forward the por- 

 tion before it, in the direction of the impulse, so 

 that every particle alternately advances and retreats. 

 But, in pursuing this idea into its details, Newton 

 fell into some errors which were pointed out by 

 Cramer, though their origin was not traced, nor the 

 reasoning corrected, till the subject was resumed by 

 Lagrange and Euler ; nor is this any impeachment 

 of the penetration of our immortal countryman. The 

 mathematical theory of the propagation of sound, 

 and of vibratory and undulatory motions in general, 

 is one of the utmost intricacy ; and, in spite of every 

 exertion on the part of the most expert geometers, 

 continues to this day to give continual occasion for 

 fresh researches ; while phenpmena are constantly 

 presenting themselves, which show how far we are 

 from being able to deduce all the particulars, even 

 R 4 



