DR. PROUT'S HYPOTHESIS. 73 



chemical molecules of oxygen, hydrogen, carbon, 

 &c. do not exist in a state of ultimate division ; 

 but that they are composed of many sub-mole- 

 cules, which he conceives are analogous in subtil ty 

 and refinement to imponderable matter.* It will 

 be shewn hereafter, that the electric spark, and 

 the spark from the collision of flint with iron, 

 steel, and other hard bodies, is imponderable 

 while in that state. It will be inquired further 

 on, whether ponderable matter in such a state 

 may not be more subtile than in the elementary 

 gaseous form ; and whether the different colours 

 of electric light, and of the flames of combustion, 

 may not depend on the different primitive colours 

 of ultimate atoms. 



Relative Quantities of Caloric in Different Bodies. 



This is one of the most difficult problems in 

 Physical Science, the very elements of which 

 have yet to be unfolded. If it be true, that the 

 whole material world is composed of gravitating 

 atoms which vary in size, and that they are sur- 

 rounded by an active, igneous, and aethereal prin- 

 ciple, which is immediately connected with all 

 their properties and changes, it is obviously an 

 object of primary importance to ascertain the 



* Bridgewater Treatise, p. 90. 



