242 FKAGMENTS OF SCIENCE. 



•which lie entirely beyond the range of the senses, the con- 

 ceptions are as truly mechanical as they would be if we 

 were dealing with ordinary masses of matter, and with 

 waves of sensible magnitude. No really scientific mind at 

 the present day will be disposed to draw a substantial dis- 

 tinction between chemical and mechanical phenomena. 

 They differ from each other as regards the magnitude of 

 the masses involved ; but in this sense the phenomena of 

 astronomy differ, also, from those of ordinary mechanics. 

 The main bent of the natural philosophy of a future age 

 will probably be to chasten into order, by subjecting it to 

 mechanical laws, the existing chaos of chemical phe- 

 nomena. 



Whether we see rightly or wrongly — whether our in- 

 tellection be real or imaginary — it is of the utmost im- 

 portance in science to aim at perfect clearness in the de- 

 scription of all that comes, or seems to come, within the 

 range of the intellect. For, if we are right, clearness of 

 utterance forwards the cause of right ; while, if we are 

 wrong, it insures the speedy correction of error. In this 

 spirit, and with the determination at all events to speak 

 plainly, let us deal with our conceptions of ether-waves and 

 molecules. Supposing a wave, or a train of waves, to im- 

 pinge upon a molecule so as to urge all its parts with the 

 same motion, the molecule would move bodily as a whole, 

 but because they are animated by a common motion there 

 would be no tendency of its constituent atoms to separate 

 from each other. Differential motions among the atoms 

 themselves would be necessary to effect a separation, and 

 if such motions be not introduced by the shock of the 

 waves, there is no mechanical ground for the decomposition 

 of the molecule. 



Thus the conception of the decomposition of compound 

 molecules by the waves of ether comes to us recommended 

 by a priori probability. But a closer examination of the 



