CONNEXION OF THE SCIENCES. 50!) 



which exhibit perfectly distinct properties when 

 united with different proportions of the same 

 active principle that transports their particles 

 from one place to another, and arranges them in 

 symmetrical forms; that gallic acid is converted 

 into pyro-gallic acid by the addition of heat 

 alone ; and the latter into another distinct sub- 

 stance by a further addition of caloric, as in the 

 formation of isomeric bodies. 



It has been asserted by innumerable writers 

 on physiology, that the phenomena of life are as 

 far removed from those of ordinary chemistry as 

 the latter from mechanics. But the Great Ar- 

 chitect of the universe has so completely con- 

 nected all the operations of nature together, that 

 it is often difficult to draw the boundary line 

 between mechanical, chemical, and vital action. 

 The mechanical force of steam is generated by 

 the chemical union of caloric with the particles of 

 water, to the expansion and contraction of which 

 we are indebted for all the phenomena of evapo- 

 ration and rain, the nourishment of vegetation, 

 and the sustenance of animal life.* The circu- 

 lation of sap through the vessels of plants is no 

 less the result of attraction than the absorption 

 of water by a sponge, or its elevation in the ca- 



* And if it be true, as there is every reason to suppose from 

 analogy, that solar light, like that of a lamp or common fire, is 

 generated by combustion, all the phenomena of nature must be 

 referred to chemical action. 



