546 INDUCTION. 



merly quoted, in which the difference between the 

 observed and the calculated velocity of sound was 

 ascertained to result from the heat extricated by the 

 condensation which takes place in each sonorous 

 vibration. This was a trial, in new circumstances, of 

 the law of the developement of heat by compression ; 

 and it certainly added materially to the proof of the uni- 

 versality of that law. Accordingly any law of nature 

 is deemed to have gained in point of certainty, by 

 being found to explain some complex case which had 

 not previously been thought of in connexion with it ; 

 and this indeed is a consideration to which it is the 

 habit of scientific men to attach rather too much value 

 than too little. 



To the Deductive Method, thus characterised in 

 its three constituent parts, Induction, Ratiocination, 

 and Verification, the human mind is indebted for its 

 most glorious triumphs in the investigation of nature. 

 To it we owe all the theories by which vast and com- 

 plicated phenomena are embraced under a few simple 

 laws, which, considered as the laws of those great 

 phenomena, could never have been detected by their 

 direct study. We may form some conception of what 

 the method has done for us, from the case of the celes- 

 tial motions ; one of the simplest among the greater 

 instances of the Composition of Causes, since (except 

 in a few cases not of primary importance) each of the 

 heavenly bodies may be considered, without material 

 inaccuracy., to be never at one time influenced by the 

 attraction of more than two bodies, the sun and one 

 other planet or satellite, making, with the reaction of 

 the body itself, and the tangential force, only four 

 different agents on the concurrence of which the 

 motions of that body depend ; a much smaller number, 

 no doubt, than that by which any other of the great 



