SIXTH ORDINARY MEETING. 4T 
There can be now no doubt that the theoretical foundation for the 
modern doctrine of ‘the conservation of energy, of which the equiva- 
lence of heat and work is a particular case, was distinctly and 
substantially laid by the genius of Newton in his wonderful scholium 
to his Third Law of Motion. 
In this scholium and in the commentary on it Newton not only 
enunciates the law of conservation of energy, so far as the state of 
experimental science in his day would permit, but also clearly antici- 
pated the so-called modern principle of Vis Viva and D’Alemhert’s 
principle. No further advance of any moment seems to have been 
made till about 100 years later Davy and Rumford proved experi- 
mentally the immateriality of heat. To Rumford is mainly due the 
eredit of having rescued the question of the nature of heat from the 
domain of metaphysics, and of having devised several ingenious 
experiments, by means of which he arrived at a remarkably approxi- 
mate value of the mechanical equivalent of heat. The next im- 
portant names in connection with the history of the theory of heat: 
are those of Fourier and Carnot. The calculations and conclusions 
of these profound mathematicians were expressed, it is true, in terms 
which to a certain extent involved the now exploded corpuscular 
theories of light and heat, but their reasoning and results were 
to such ‘an extent independent of any particular theory that the 
elements involving the truth of these untenable hypotheses are 
capable of being almost entirely eliminated, leaving results which 
have proved of the greatest use in the development of the true 
theory of energy. Perhaps the most important of the many valuable 
contributions of Clausius to the theory of heat was his adaptation 
of the theorem of Carnot, so as to make it consistent with the prin- 
ciple of the equivalence of heat and work. 
To Joule, the great English physicist, is undoubtedly due, as has 
been conclusively shown by Prof. Tait, the credit of having placed 
the grand law of the conservation of energy, of which the first main 
principle of the mechanical theory of heat is but a particular case, 
on a sure experimental foundation. By means of some of the most 
ingenious and refined experiments of modern times, Joule deter- 
mined that 772 foot-pounds of work, if converted into heat, would 
raise | pound of water 1° F., or that to produce a quantity of heat 
sufficient to raise 1 kilogramme of water through 1° C. work must 
be consumed to the extent of 424 kilogrammetres, and thus placed 
