Proceedings of the British Association, 235 



velocity of oxygen was found to be *9500 by experiment, and by 

 calculation *9487. Carbonic acid being much heavier than air, gave 

 the number *812. Carburetted hydrogen gave '1322 as the velocity of 

 its effusion. Hydrogen gave as the velocity of effusion 3*613 by 

 experiment, which was very nearly the amount given by theory. The 

 interference of friction, even of minute orifices, was then described, 

 and shown to admit of easy correction. Some useful applications 

 were mentioned ; as in the manufacture of coal gas, where it is de- 

 sirable 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, and as the superior carburetted hydrogen is 

 heaviest, it would be easy to construct an instrument to regis- 

 ter 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, the air exhausted by the pump, and 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 greater than that of oxygen. Carbonic acid is found to be more 

 transpirable than oxygen — or even, under low pressure, than atmos- 

 pheric air. The transpiration of hydrogen is one-third more rapid 

 than that of oxygen. The applicability of this process of experi- 

 menting to the explanation of exosmose and endosmose action in the 

 passage of fluids through porous bodies was pointed out. 



Mr. Bain made some observation to the effect, that Prof. Graham's 

 researches went to explain many meteorological phenomena, but 

 particularly the suspension in the atmosphere of masses of aqueous 

 vapour, in the form of clouds. 



'On Recent Experiments on the Gas Voltaic Battery,' by Prof. 

 Grove. — No previous description of the Gas Battery having been 

 given before the Association, Prof. Grove entered into an explanation of 

 the action of hydrogen gas upon spongy platina, and gave a descrip- 



