28 REPORT—1845. 
water appeared like a silver plate. The application of the principles involved in these 
phenomena to the tempering of metals was then explained. If a metal to be tem- 
pered is in a highly incandescent state, the necessary hardening will not take place on 
plunging it into water. It is therefore necessary that a certain temperature should 
be observed. Experiments were made to show that the repulsive power of the sphe- 
roidal fluid existed, not merely between it and the hot plate, but between it and other 
fluids. ther and water thus repelled each other, and water rested on and rolled 
over turpentine. The bursting of steam-boilers came next under consideration; and 
it was shown that many serious explosions may be referred to the phenomena under 
consideration. In a great many cases, the explosions have occurred during the cool- 
ing of the boilers after the withdrawal of the fire. An experiment was shown in proof 
of the view entertained by M. Boutigny. A sphere of copper, fitted with a safety- 
valve, was heated, and a little water being put into it, it was securely corked up, and 
withdrawn from the lamp. As long as the metal remained red, everything was quiet; 
but upon cooling, the cork was blown out with explosive violence. The concluding 
experiment excited great interest—the production of ice in a vessel at a glowing red 
heat. It was successfully performed by M. Boutigny, in the following manner :— 
A deep platina capsule was brought to a glowing red heat, and at the same moment 
water and liquid sulphureous acid, which had been preserved in the liquid state by 
a freezing mixture, were poured into the vessel. ‘he rapid evaporation of the vola- 
tile sulphureous acid, which enters into ebullition at the freezing-point, produced such 
an intense degree of cold, that a large lump of ice was immediately formed, and being 
thrown out of the red-hot vessel, handed round for examination. 
On a New Property of Gases. By Professor Grauam, M.4A., F.R.S. L. § E. 
After explaining the law which regulated the diffusion of gases, and stating the 
fact, that the lighter gases diffused themselves much more speedily than the more 
dense ones,—the velocity of their diffusion being equal to the square root of their 
densities,—he proceeded to relate his experiments on the passage of gases into a 
vacuuin. To this passage the term Effusion has been applied. The velocity of air 
being 1-, the velocity of oxygen was found to be 0-9500 by experiment, and by caleu- 
lation 0°9487. Carbonic acid being much heavier than air, gave the number 0°821, 
the theoretical number being 0°812. Carburetted hydrogen gave 0°1322 as the velo- 
city of its effusion, the theoretical number being 1°341. Hydrogen gave as the velo- 
city of effusion 3°613 by experiment, which was nearly the amount given by theory 
(0°379). ‘The interference of friction, even of minute orifices, was then described, 
and shown to admit of easy correction. Some useful applications were mentioned ; 
asin the manufacture of coal-gas, where it is desirable to ascertain the quality, as well 
as the quantity of gas manufactured. As the gas will pass the orifice on its way to 
a vacuum the quicker the lighter it is, and the more slowly as it increases in density, 
andas the superior carburetted hydrogen is heaviest, it would be easy to construct an 
instrument to register this velocity, and thus mark at once the required quality and 
quantity of gas. It was also proposed that an instrument might be used in mines to 
detect the presence of light carburetted hydrogen (fire-damp). The passage of gases 
under pressure through porous bodies was termed by Prof. Graham, Transpiration. 
The mode adopted in experiment was, to take a glass receiver, open at the top, which 
was closed with a plate of stucco. This was placed on an air-pump, and the air ex- 
hausted by the pump, the velocity with which the air passed through the stucco being 
marked by the mercurial gauge of the pump. The transpiration of atmospheric air 
was found to be more rapid than that of oxygen. Carbonic acid is found to be more 
transpirable than oxygen, or even, under low pressure, than atmospheric air. The 
transpiration of hydrogen is one-third more rapid than that of oxygen. The appli- 
cability of this process of experimenting to the explanation of exosmose and endosmose 
action in the passage of fluids through porous bodies was pointed out. 
On the Action of Gases on the Prismatic Spectrum. By Dr. Mitizr. 
Referring, in the first instance, to the experiments of Sir D. Brewster on the 
changes produced en the fixed lines of the prismatic spectrum by varieus absorptive 
