362 JAMES WATT. 



new instrument presented essential improvements in the 

 mechanical parts, in the regulators, in the method of 

 appreciating the power of the wind ; but it will excite 

 astonishment to learn that its harmonic qualities were 

 not less remarkable, and that they charmed professional 

 musicians. Watt solved an important part of the prob- 

 lem : he arrived at the temperament assigned by a man 

 learned in the mystery, in aid of the phenomenon of the 

 vibrations then but ill understood ; and which he could 

 not have dived into, but in the profound though obscure 

 work of Dr. Smith,* of Cambi'idge. 



PRINCIPLES OF THE STEAM-ENGINE. 



I have now reached the most brilliant portion of Watt's 

 life, and also, I fear, the most difficult part of my task. 

 The immense importance of the inventions of which I am 

 about to treat, cannot be doubted for one moment ; but I 

 may not succeed in rendering them suitably appreciated, 

 without entering into intricate numerical comparisons. 

 In order that these comparisons, if they become essential, 

 may be easily seized, I will present you, in the most com- 

 pact manner possible, with the delicate notions of physics 

 on which we shall have to rest them. 



By the effect of simple changes of temperature, water 

 may exist in three perfectly different conditions ; in the 

 solid state, in the liquid state, and in the aerial or gaseous 

 state. Below zero on the scale of the centigrade ther- 

 mometer, water becomes ice ; at 100° it rapidly assumes 

 the form of gas ; in all the intermediary temperatures it 

 remains fluid. 



* Dr. Robert Smith's work, here aHuded to, was intituled Eirmonics, 

 or the Philosophy of Musical Sounds, and printed in 1760. He was also 

 the author of the well-lsnown System of Optics. — Translator. 



