250 J. W. SLATER, ESQ., ON 



of the heavenly bodies. In proof we need merely refer to 

 the spectroscope, the indications of which would be 

 utterly unmeaning had we no knowledge of physics and 

 chemistry. 



Chemistry is now known to be largely indebted to biology. 

 The latter science aids us in determining the molecular 

 constitution of compounds. We cannot understand the 

 phenomena of fermentation and putrefaction, the formation 

 of nitrates and of ammonia without a knowledge of the vital 

 action of micro-organisms. 



Such cases of mutual obligation are sure to become 

 more abundantly known the more our researches are 

 extended. 



Further, the phenomena of physics are quite as general as 

 those of astronomy, since we recognise the heavenly bodies 

 onl^^ by the light which they emit or reflect. It is also difficult 

 to conceive that we can anywhere have matter acted upon 

 by certain of the forms of energy, such as heat, light, or 

 electricity, without the possibility of chemical changes. 

 Chemical phenomena are thus found to be no less general 

 than those which form the subject matter of astronomy and 

 of physics. 



Comte's classification of the respective branches of physics 

 is founded on the same principles which we have mentioned 

 above, and it is by no means happy. He arranges in a 

 linear series the disciplines which treat of gravitation, heat, 

 sound, light and electricity. Now it must surely be admitted 

 at once that the phenomena of light and electricity, the 

 former of which agencies travels through the depths of space, 

 whilst the latter probably pervades all matter, are vastly 

 more general than those of sound. But the classification of 

 the sciences in a linear series, on any principles, will be 

 found practicable only by dint of arbitrary assumptions and 

 by the neglect of obvious considerations. Comte certainly 

 rejects the so-called imponderables. He does not admit, but 

 neither does he deny the existence of the " ether " whose 

 undulations aff'ect us as light. Some credit may be awarded 

 to him for taking this stand, if we remember that at the time 

 when the Philosojyhie Positive was written (1830-1842), many 

 French thinkers still clung on in an unhappy devotion to the 

 conception of " caloric " as a substantive entity. 



Electricity, according to Comte, forms a natural transition 

 to chemistry. Yet the relations of chemistry and heat are 

 now found, thanks to the labours of Berthelot and Thomson, 



