420 THE POPULAR SCIENCE MONTHLY. 



and "molecules;" and, though still with knowledge and sensibility to 

 know and feel our degraded position " so abject ! yet alive " with 

 no power to apply our knowledge in effort to extricate, and to elevate 

 ourselves. We might still have the knowledge of good and evil ; but, 

 having no power to foster the one, or to resist the other, this knowl- 

 edge, with all its inestimable consequences all the aspirations which 

 it awakens, and all the incentives to noble deeds which it, in combina- 

 tion with effort, alone makes possible would be lost. And with it, we 

 might almost say, there would again be no death, for all mutation now 

 being but changes in the indestructible atoms of matter, by means 

 of its motion, also indestructible and eternal, there would be little left 

 to die, as there would again be little left to live for. For all this, I see 

 no compensation in the doctrines now so clearly and frankly presented. 







CELESTIAL CHEMISTET. 1 



By T. STEKEY HUNT, LL. D., F. E. S. 



AMONG the most significant advances in chemical theory are 

 those relating to the action of heat on bodies. If we define 

 chemistry, as I have been tempted to do, as that science which treats 

 of the relations to one another of the different forms of mineral (i. e., 

 unorganized) matter, and their transformations under the physical 

 agencies of heat, light, and electricity, we shall see how difficult it is, 

 in a sketch like this, to draw the line between physics and chemistry. 

 This becomes still more evident when we see in light the chemical 

 constitution of matter, as it were, revealed and made visible to us by 

 the spectroscope, or study the electric current parting in a mysterious 

 manner the components of bodies. Time would fail us to follow the 

 trains of thought thus opened, but I cannot forbear to say somewhat 

 of the relations of temperature to chemical species, and of the power 

 of heat to unloose the bonds of chemical combination. The admirable 

 researches of Grove, followed by those of Henri St.-Claire Deville and 

 his fellow-laborers, have shown us that, at an elevated temperature, 

 such bodies as water, hydrate of potassium, and hydi'ochloric acid, are 

 more or less completely resolved into their constituent elements, the 

 affinities of which are suspended. In the principle of dissociation by 

 heat we have an explanation of many chemical reactions hitherto enig- 

 matical. The decomposition of bodies by heat is, moreover, assimi- 

 lated to the phenomenon of volatilization : the rate of decomposition at 

 a given temperature varying with the pressure, and with the nature 

 of the atmosphere which surrounds the unstable body. The phenom- 



1 Extract from Dr. Hunt's Address at the Northumberland Centennial, on " A Cen- 

 tury's Progress in Theoretical Chemistry." 



