849 



same subject, afforded grounds for assuming the existenceof a relation 

 in the transpirability of different gases, that is, their passage through 

 capillary tubes, of an equally simple nature as that which is recog- 

 nized 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 properties, 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. Under such impressions he has devoted an unusual 

 amount of time and attention to the determination of this class of 

 numerical constants. As the results, too, were entirely novel, and 

 wholly unprovided for in the received view of the gaseous constitu- 

 tion, of which indeed they prove the incompleteness, it was the more 

 necessary to verify every fact with the greatest care. 



The most general and simple of the results is, that the transpira- 

 tion velocity of hydrogen gas is exactly double that of nitrogen gas. 

 These gases, it will be remembered, have a less simple relation in 

 density, namely 1 to 14?* This was the conclusion of his former paper 

 respecting the transpiration of these gases, and he has obtained 

 since much new evidence in its favour. The transpirability of car- 

 bonic oxide, like the specific gravity of that gas, appears also to be 

 identical with that of nitrogen. 



The result which may be placed 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, aftd 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 equally precise as 

 that betn^een nitrogen and hydrogen. The densities calculated from 

 the atomic weights of oxygen and nitrogen, namely, 16 and 14, 

 being 1 for oxygen, 0*9010 for air and 0'8750 for nitrogen, the ob- 

 served times of transpiration of equal volumes of the same gases are 

 for oxygen 1, air 0-8970 to 0-9010, and for nitrogen 0-8708. The 

 result for carbonic acid, which is perhaps next in interest, appears 

 at first anomalous. It is, that the transpiration time of this gas is 

 inversely proportional to its density when compared with oxygen, or 

 0*7272, the time of oxygen being 1, their velocities will of course be 

 directly as their densities. It is to be remembered, however, that 

 carbonic acid is a compound gas, containing an equal volume of 

 oxygen. The second constituent, carbon, which increases the weight 

 of the gas, appears to give additional velocity to the oxygen in the 

 same manner and to the same extent as increased density from pres- 

 sure or from cold increases the transpiration velocity of pure oxygen 

 itself. A result of this kind shows at once the important chemical 



