12 SCIENTIFIC THOUGHT. 



and of magnetism. On the other side there was the 

 highly developed theory of sound, which had succeeded 

 in explaining and analysing the properties of sound- 

 ing bodies by studying experimentally and mathe- 

 matically the vibrations of sounding strings, membranes 

 and plates, and also of the air in organ-pipes and other 

 7. musical instruments. Acoustics, the branch of science 



Undulatory 



theory which treats of these phenomena, was, next to physical 



prepared by " J 



acoustics, astronomy, the furthest developed and best founded of 

 the physical sciences. By following up the elemen- 

 tary and primitive experience, known already to the 

 ancients, that sound is everywhere to be traced to the 

 vibrations or the tremor of some body which has been 

 struck or otherwise excited, a very complete theory, 

 substantiated by many experiments, had been built up. 

 Common-sense and everyday experience had originally 

 suggested this line of inquiry and explanation. 1 No 

 other physical science was so early in possession of the 

 right road of inquiry. In astronomy and optics the 

 suggestion of common-sense, which regards the earth 

 as stationary and light as an emission travelling in 

 straight lines, had indeed allowed a certain amount of 

 definite knowledge, based upon measurement and cal- 



1 Acoustics is probably the only cover}-, like universal gravitation, or 

 physical science where this has luminiferous undulations, we take 

 been the case; as is well re- our stand upon acknowledged truths, 

 marked by Whewell in his ' History ; the production and propagation of 

 of the Inductive Sciences.' He sound by the motion of bodies 

 there contrasts acoustics with as- , and of air; and we connect these 

 tronomy and optics. He might with other truths, the laws of 

 have added dynamics, where Gal- motion, and the known properties 

 ileo's principle of inertia similarly of bodies, as for instance then- 

 reversed the dicta of common-sense. elasticity. Instead of epochs of 

 Whewell says (vol. ii. p. 237) of discovery, we have solutions of 

 acoustics : " Instead of having to problems. " 

 travel gradually towards a great dis- 



