1874.] Notices of Books. 235 
What must result? ‘The mechanical energy of the universe 
will be more and more transformed into universally diffused heat, 
until the universe will no longer be a fit abode for living beings.”’ 
ah “If we could view the universe as a candle not lit, 
then it is perhaps conceivable to regard it as having been always 
in existence; but if weregard it rather as a candle that has been 
lit, we become absolutely certain that it cannot have been burning 
from eternity; and that a time will come when it will cease to 
burn. We are led to look to a beginning, in which the particles 
of matter were in a diffuse chaotic state, but endowed with the 
power of gravitation, and we are led to look to an end in which 
the whole universe will be one equally heated inert mass, and 
from which everything like life, or motion, or beauty, will have 
utterly gone away.” 
The final chapter discusses the position of life:—An animal is 
defined asa machine of a delicacy which is practically infinite, the 
condition or motions of whichwe are utterly unable to predict. And 
what is life? ‘* Life is not a bully who swaggers out into the open 
universe, upsetting the laws of energy in all directions, but rather 
a consummate strategist, who, sitting in his secret chamber, 
before his wires, directs the movements of a great army.” 
Prof. Stewart has surely misread a statement made by Rumford :— 
“‘Tt was seen that in order to do work,” says our author, p. 163, 
‘(an animal must be fed; and, even at a still earlier period 
Count Rumford remarked that a ton of hay will be administered 
more economically by feeding a horse with it, and then getting 
work out of the horse, than by burning it as fuel in an engine.’ 
Mmgeord words are these:* . .-. ‘* Heat may thus: Be 
produced merely by the strength of a horse, and, in case 
of necessity, this heat might be used in cooking victuals. But 
no circumstances could be imagined in which this method of 
procuring heat would be advantageous ; for more heat might be 
obtained by using the fodder necessary for the support of the horse 
as fuel.” ‘This latter must be the right view of the case, for part 
of the energy derived from the consumed hay is dissipated in the 
very working of the horse’s great muscular mechanism, and a 
part of the work done by the horse is dissipated as heat by the 
friction of the working parts of the machine which it moves, 
whether that machine be one for producing heat by friction, as 
in Rumford’s experiment, or for any other purpose. 
Prof. Stewart’s work is interesting and very readable. We 
commend it to all readers, whether scientific or otherwise, who 
are desirous of learning the most recent ideas connected with 
the various transmutations of the different physical forces. 
* “An Enquiry Concerning the Source of the Heat which is Excited by 
Friction.” Read before the Royal Society, Jan. 25th, 1798. The italics are 
our own. 
