350 
PROFESSOR GRAHAM ON THE MOTION OF GASES. 
cision of result in the passage of Liquids through capillary tubes^ which has been 
fully confirmed by M. Regnault*. 
The experiments of my former paper afford good grounds for assuming the ex- 
istence of a relation in the transpirability of different gases, of an equally simple 
nature as that which is recognised among the specific gravities of gases, or even as 
the still more simple ratios of their combining volumes. Compared with solids and 
liquids, matter in the form of gas is susceptible of small variation in physical pro- 
perties, and exhibits only a few grand features. These differences of property which 
are preserved amidst the prevailing uniformity of gases, may well be supposed to be 
among the most deep-seated and fundamental in their nature with which matter is 
endowed. It was under such impressions that I have devoted an amount of time 
and attention to the determination of this class of numerical constants, which might 
otherwise appear disproportionate to their value and the importance of the subject. 
As the results, too, were entirely novel, and wholly unprovided for in the received 
view of the gaseous constitution, of which indeed they prove the incompleteness, it 
was the more necessary to verify every fact with the greatest care. 
Perhaps the most general and simple result which I can offer is, that the transpira- 
tion velocity of hydrogen is exactly double that of nitrogen. These gases it will be 
remembered have a less simple relation in density, namely 1 to 14. This was the 
conclusion respecting the transpiration of these gases in my former paper, and I have 
obtained since much new evidence in its favour. The transpirability of carbonic 
oxide, like the specific gravity of that gas, appears also to be identical with tliat of 
nitrogen. 
The result which I would place next in point of accuracy and importance is, that the 
transpiration velocity of oxygen is related to that of nitrogen in the inverse ratio of 
the densities of these gases, that is as 14 to 16. In equal times it is not equal volumes 
but equal weights of these two gases that are transpired; the more heavy gas being 
more slowly transpired in proportion to its greater density. Mixtures of oxygen and 
nitrogen have the mean velocity of these two gases, and hence the time of air is also 
found to be proportional to its density when compared with the time of oxygen. 
The relation between nitrogen and oxygen is, I believe, equally precise as that be- 
tween nitrogen and hydrogen. The densities calculated from the atomic weights of 
oxygen and nitrogen, namely, 16 and 14, being 1 for oxygen, O'OOlO for air and 
0*8750 for nitrogen ; the observed times of transpiration of equal volumes of the same 
gases are for oxygen 1, air 0*8970 to 0*9010, and for nitrogen from 0*8680 to 0*8708. 
These slight deviations I look upon as of the same character as those which accu- 
rate determinations of the densities of the same gases indicate from their calculated 
or theoretical density ; the observed densities of air and nitrogen being 0*9038 and 
* Rapport sur un Memoire de M. le Docteur Poiseuille, ayant pour titre, “ Recherches experimentales sur 
le mouvement des liquides dans les tubes des trbs-petits diametres.” Annales de Chimie et de Physique* 
s^rie, t. vii. p. 50. 
