1872.] Heat. 401 
the new arrangement. It also contains some valuable remarks on total 
reflection and the transmitting power of various media, which are too long 
for quotation, and cannot be profitably given in abstract. 
HEAT. 
M. F. Tommasi has endeavoured to show the possibility of converting into 
dynamic work the expansion produced in liquids by heat; and the easy appli- 
cation of this motive force to the hydraulic press. He endeavours to show 
that by the expansion of oil instead of water, the pressure being caused to act 
directly upon the piston of the press, five-tenths of the quantity of heat 
employed in the ordinary steam engine produces the same degree of tension. 
The apparatus is very simple, consisting merely of a boiler in communication 
with a piston-box, the boiler being filled with colza or other oil, and heated by 
means of gas. It would appear that there is effected over other machines 
a saving of about 75 per cent. 
The “ Berichte der Deutschen Chemischen Gesellschaft zu Berlin,’’ has an 
important paper on the specific heat of carbon. Dulong and Petit showed by 
experiments with twelve of the metals, that the product of the atomic weight 
and specific heat—in other words, the so-called atomic heat—had the same 
value, about 6°5, for all elements. Experimentalists have, from time to time, 
observed many striking departures from that law, and a comparison made by 
the author of the paper, H. F. Weber, of the numbers obtained by Regnault, 
De la Rive, Kopp, and Willner, as representing the specific heat of carbon, 
clearly shows that the different allotropic modifications of this element have 
very different specific heats, no one of which obeys Dulong and Petit’s law; 
while the values assigned by these physicists to the specific heat of any one 
modification vary within wide limits. This is probably due to the fa& that the 
specific heat of carbon in all its allotropic conditions varies with the tempera- 
ture. Experiments with two large diamonds, conducted in the physical 
laboratory of Professor Helmholtz, in Berlin, have shown that the specific heat 
of carbon increases with the temperature to a degree surpassing any other 
substance, the specific heat of diamond being trebled by an increase of 
temperature from 0° to 200° C. 
The following experiment has the advantages of certainty in its perfor- 
mance and of novelty. Take a wide glass tube open at both ends, and some 
little distance into the interior push a piece of fine wire gauze. If the gauze 
is now heated to redness over an ordinary Bunsen burner and then removed, 
it will shortly emit a shrill note for five to ten seconds. 
The Real Evaporative Efficiency of Steam-Boilers Determined. — The 
American Institute of the State of New York have made public the 
result of an important series of trials of steam-boilers which was made at 
their last annual exhibition. The committee appointed to decide upon the 
merits of all steam apparatus and machinery entered at the “‘ Fair,” consisted 
of R. H. Thurston, Professor of Mechanical Engineering at the Stevens Insti- 
tute of Technology, Chairman; and T. J. Sloan and Robert Weir, well-known 
engineers, Members. To secure an accurate determination of the amount of 
water passing out of the boilers, both evaporated and unevaporated, it was led 
into a large surface condenser. The weight of the water of condensation and 
of the condensing water was exactly measured, and the temperature of the 
water of condensation and the condensing water, of the steam in the boiler 
and of the entering feed and injection water, was obtained by delicate thermo- 
meters. The greatest care was taken to insure such accurate determination 
as should make the results of these trials valuable as standards with which to 
compare those of future similar trials. The log was kept by students selected 
from advanced classes of the Stevens Institute of Technology, and under the 
supervision of the chairman, himself a professional and experienced engineer. 
The committee thus obtained results that are extremely valuable to the 
engineer, as exhibiting the true efficiency of what they considered good boilers 
of quite dissimilar forms, and hardly less useful to the physicist, as giving 
the modulus of efficiency of large evaporating apparatus. The arrangement 
VOL. II. (N.S.) 3 F 
