Ixii REPORT—1857. 
cases, the moverient of masses is transformed into molecular motion; and this 
reappears as heat, electricity, and chemical action; and the amount of the 
transformed action definitely corresponds to the mechanical force which was 
apparently lost. 
In the cases just considered, mechanical action is éofiverted into molecular. 
But molecular actions of different kinds are themselves in like matiner 
interchangeable. Thus, when “ight is absorbed, vis viva is apparently lost ; 
but—not to speak of phosphorescence, in which the light absorbed, or a portion 
of it, is again given out—in all such cases, heat and chemical action are 
developed, and in amount corresponding to the loss. Hente the apparent 
exceptions to the principle are in reality confirmations of it; and we learn 
that the quantity of force in nature is as unchangeable as the quantity of 
matter. 
This, however, is not true of the quantity of available force. It follows 
from Carnot’s law, that heat can be converted into mechanical work only 
when it passes from a warmer to a colder body. But the radiation and com- 
duction by which this is effected, tend to bring about an equilibrium of tem 
perature, and therefore to annihilate mechanical force: and the same destruc- 
tion of energy is going forward in the other processes of nature. Thus, it 
follows from the law of Carnot; as Professor Thomson has shown, that the 
tiniverse tends to a state of eternal rest ; and that its store of available force 
mist be at length exhausted, unless replenished by a new act of Creative Power. 
Mr. Rankine has attempted, in another method, to combine the physical 
sciences into one system, by distinguishing the properties which the various 
classes of physical phenomena possess in common, and by taking for axioms 
propositions which comprehend their laws. The principles thus obtained are 
applicable to all physical change; and they possess all the certainty of the 
facts from wliich they are derived by induction. The subject-matter of the 
science so coustituted is energy, or the capacity to effect changes; and ifs 
fundamental principles are— 1st, that all kinds of energy and work are homi6- 
geneous, or, in other words, that any kind of energy may be made the meaiis 
of performing any kind of work ; and 2nd, that the total energy of a substance 
éannot be altered by the mutual action of its parts. From these principles 
the author has deduced some very general laws of the transformation of 
energy, which include the known relations of physical forces. 
I have occupied your time so largely with the sciences of one section, that 
I cannot do more than advert to one or two topics connected with the others, 
which have struck my own mind, although, from my limited acquaintance 
with the subjects, I could not venture to say that they are absolutely the 
most deserving of notice. 
Aimong the most remarkable of the recent discoveries in inorganie che- 
mistry are those of MM. Wéhler and Deville, relative to silicon and boron, 
Each of these substances is now proved to exist in three very different states, 
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