PROFESSOR GRAHAM ON THE MOTION OF GASES. 
377 
observations were made ; the thermometer being 72° to 74°, and barometer 30’248 to 
30'218 inches. 
The times of air were 858, 860 and 859 seconds ; the times of carbonic acid 711 
and 712 seconds ; the times of chlorine 670, 670, 670 and 670 seconds ; the time of 
air again 866 and 867 seconds. A slight increase in the air-time is observed, after 
the chlorine experiments, but I would refer this increase more to the rise of two de- 
grees in temperature between the first and last observations, than to any derange- 
ment in the apparatus. Taking the last observed air as the standard of comparison 
for the chlorine, and the first observed air for the carbonic acid, we find — 
Air=l. 
Oxygen =1. 
Transpiration time of chlorine 
Transpiration time of carbonic acid... 
0*7732 
0*8282 
0*6959 
0*7454 
But the true transpiration time of chlorine gas is probably less than 0*6959, for the 
true time of carbonic acid is certainly less than 0*7 454, the time obtained above for the 
latter gas. The present capillary, it has been already remarked, is one of too small 
resistance to bring out the true transpiration time of a gas whose effusion rate differs 
very widely from its transpiration rate. The present experiment indeed is not incon- 
sistent with the true transpiration time of chlorine, being 2 or 3 per cent, lower than 
that observed, or falling as low as 0*66, that is, two-thirds of the time of oxygen. 
(3.) The transpiration of chlorine was also observed by means of the long capillary 
M, 52'5 inches in length, with the same six-pint glass globular receiver as aspirator- 
jar. The fall observed by the gauge barometer was only 3 inches, or from 28*5 to 
25*5 inches. Thermometer 58°, barometer 29*742 inches. 
The time of air was 1907 and 1911 seconds; of chlorine 1432 and 1395 seconds. 
The difference of 37 seconds in the two observed times of chlorine, which is so con- 
siderable, arose from the action of chlorine upon the mercury ; for notwithstanding 
that the latter was covered with water, its surface became so uneven that the obser- 
vations could not be made with any great nicety. The first observation of chlorine 
gives the time of that gas 0*7501 referred to air, and 0*6751 referred to oxygen ; the 
second observation gives the time of chlorine 0*7307 referred to air, and 0*6576 re- 
ferred to oxygen. Calculating from 1413*5 seconds, the mean of the two observed 
times for chlorine, we obtain — 
Air = l. 
Oxygen =1. 
Transpiration time of chlorine 
0*7404 
0*6664 
The transpiration time of chlorine appears therefore to be about two-thirds of the 
time of oxygen ; or, chlorine passes through a tube with 1^ time the velocity of 
oxygen. 
