May 14, 1885] 
NATURE 
27 
unlimited applicability. Down to the present moment 
we are, however, not yet ina position to derive a com- 
plete argument for its truth from the general principles of 
kinetics. Our analytic methods are inadequate even to 
the problem of completely determining the movement of 
three bodies reciprocally attracting oneanother. In thecase, 
however, of motion which we perceive as heat, there are 
myriads of atoms engaged, all in the most irregular move- 
ment, and influenced by forces the nature of which is still 
almost wholly unknown to us. It is highly probable that 
the peculiar difficulty of reducing thermal motion into 
other forms of mechanical energy, which is expressed in 
Carnot’s thesis, is due to the circumstance that thermal 
motion is a completely “unregulated” movement, that 
is, that there is no kind of similarity between the move- 
ments of atoms immediately neighbouring one another. 
Even in the case of the most rapid vibrations of light 
and sound, on the other hand, the movements and con- 
ditions of neighbouring atoms are so much the more 
similar to one another the nearer they are to one 
another. These, therefore, I am in the habit of calling 
“regulated” in antithesis to thermal motion. Sir W. 
Thomson has introduced for this conception the name 
of “dissipation of energy.” Prof. Clausius denotes the 
quantitatively determined measure of the same magni- 
tude by a more abstract name, “entropie.” The dissipa- 
tion of energy is capable, according to Carnot’s law, by 
every known process of nature in the inorganic world, 
only of constant increase, never of decrease, and this 
leads to the much-talked-of conclusion that the universe 
is tending towards a final state of absolute unchangeable- 
ness with stable equipoise of all its forces under the 
establishment of complete equipoise of temperature, as 
our author expressed it in the year 1852 (Art. LIX., “ On 
a Universal Tendency in Nature to the Dissipation of 
Mechanical Energy ”). 
On the other hand the ascertained laws of dynamics 
yield the deduction that if we were able suddenly to 
reverse the total movements of the total atoms of an iso- 
lated mechanical system the whole system would of 
necessity retraverse all the states which up to that point 
of time it had passed through. Therewith also would all 
the heat generated by friction, collision, conduction of 
electrical currents, &c., return into other forms of energy, 
and the energy which had been dissipated, would be all 
recovered. Such a reversion, however, is a postulate 
beyond the power of human means to fulfil. We have 
no agency at our disposal by which to regulate the move- 
ment of atoms. Whether, however, in the extraordinarily 
fine structure of organic tissues a mechanism capable of 
doing it exists or not is a question not yet to be answered, 
and I deem it very wise on the part of Sir W. Thomson 
that he has limited all his theses respecting the necessity 
of increasing dissipation by restricting their validity to 
“inanimate matter.” 
The recognition of this scientific law of so universal 
applicability and so rich in consequences is, be it repeated, 
due in the first place, through Carnot, to an erroneous 
assumption regarding the nature of heat. The universal 
demonstration given by him of the principle, a demon- 
stration which in his day appeared completely satisfactory, 
is based purely on this assumption. And, what is still 
more noteworthy, it is hardly to be supposed that the 
principle in question could have been deduced from the 
more correct view—namely, that heat is motion, seeing 
that we are not yet in a position to establish that view on 
a completely scientific basis. The two natural philoso- 
phers, moreover, who brought Carnot’s and Joule’s prin- 
ciples into harmony with each other, and whom we have 
to thank for our present knowledge on this subject, are 
able to refer their conclusions only to an axiom general- 
ising the experience that heat tends ever to expand, never 
to concentrate. Sir W. Thomson expresses this axiom in 
the following terms:—‘‘It is impossible by means of 
inanimate material agency to derive mechanical effect 
from any portion of matter by cooling it below the 
temperature of the coldest of the surrounding objects.” 
The reviewer has, further, succeeded in demon- 
strating that the peculiar limitation affecting the trans- 
formation of heat into other forms of work likewise 
applies to other classes of motions revolving on them- 
selves, so long as no external forces are brought into 
play directly opposing or accelerating the internal 
motion.! 
When by J. P. Joule’s experiment it was demonstrated 
that the basis of Carnot’s proof was defective, it might 
have been apprehended that along with the element of 
error the element of truth in it would also be rejected. It 
must therefore be regarded as a special merit on the part 
of Prof. Clausius and Sir W. Thomson that, while re- 
moving the mistakes, they brought the truth into precise 
expression and into universal recognition, and that the 
recent theory of heat has become so fruitful in discoveries 
respecting the most secret connections between the 
different physical qualities of bodies in nature. 
The second volume of these Reprints contains chiefly 
the researches having relation to the laying of the first 
submarine telegraph cable. The motion of electricity in 
these cables undergoes a peculiar retardation in conse- 
quence of the fact that the conducting-wire separated 
from the sea-water, which is likewise a tolerably good 
conductor, only by a thin isolating layer of gutta-percha, 
forms an enormous Leyden jar, which must first be 
charged with the electricity entering it before the current 
will pass with full force along the whole length of the wire 
to the other end. The physical laws of the processes 
which here come into play were generally known, but a 
far-searching mathematical investigation was still needed 
to determine the whole procedure of these currents and 
to ascertain the amount of influence exercised on them 
by the dimensions and conductivity of the wire, by the 
neighbourhood of other wires, and by the particular 
quality of the gutta-percha, as also to arrive at a know- 
ledge of the conditions under which the most rapid series 
of signals might be transmitted and received at the 
opposite end. 
All these questions our author disposed of thoroughly 
and exhaustively, having also to contend with opposition 
to his views based on observations made under restricted 
conditions on other cables. He was then a comparatively 
little-known young man, and did not enjoy that recogni- 
tion and authority now everywhere freely accorded him. 
To this were joined mechanical problems connected 
with the sinking or eventual raising and repairing of 
* H. yon Helmholtz, ‘‘Studien zur Statik monocyklischer Systeme.” 
Sitzungsberichte der Berliner Akademie, 1884, Marz 6, 27, und Juli ro. 
