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 knowledge, with all its inestimable consequences—all the aspirations which it awakens, and all the incentives to noble deeds which it, in combination 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.
By T. STERRY HUNT, LL. D., F. R. S.
MONG 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 hydrochloric 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 enigmatical. The decomposition of bodies by heat is, moreover, assimilated 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-
- ↑ Extract from Dr. Hunt's Address at the Northumberland Centennial, on "A Century's Progress in Theoretical Chemistry."