386 
PROFESSOR GRAHAM ON THE MOTION OF GASES. 
The transpiration of equal volumes becomes slower as the temperature rises. The 
experiments which follow upon air, carbonic acid and hydrogen, were made upon 
different days with slightly different barometric pressures, so that the absolute times 
of one gas cannot be compared with another ; but this is unnecessary for our present 
purpose. The capillary employed was M, 52'5 inches in length, and of great resist- 
ance. 
Table XIV. — Transpiration of equal volumes at different temperatures. 
Temperature. 
Time in seconds. 
Air. 
Carbonic acid. 
Hydrogen. 
32 Fahr. 
1054*1 
857*9 
545*4 
59 
1092*8 
897*4 
557*8 
86 
1133*4 
931*5 
577*7 
113 
1175*7 
969*4 
598*8 
140 
1211 ' 
993*9 
615*9 
The difference of time of transpiration at the two extreme temperatures, 32° and 
140°, is 157*9 seconds for air, 136 seconds for carbonic acid, and 70*5 seconds for 
hydrogen. The differences, calculated in the proportion of the transpiration times of 
the same gases at the temperatures usually observed (56° to 74°), namely air 0*9, 
carbonic acid 0‘73, and hydrogen 0'44, are for carbonic acid 128*1 seconds instead of 
136, and for hydrogen 73*2 seconds instead of 70'5. It would be unsafe to conclude 
from these small deviations that the transpiration of the three gases in question is 
unequally affected by heat in the range of temperature from 32° to 140°; for at 
temperatures distant from the temperature of the atmosphere, the unavoidable errors 
of observation increase in magnitude. The increment upon the time of air was 
156'2 seconds, and upon hydrogen 62*8 seconds, at 140°, in a repetition of the same 
experiments. 
My most unexceptionable experiments all concur in showing that no sensible 
change takes place in the transpiration ratios of hydrogen, nitrogen and carbonic 
oxide, at temperatures so high as 347° Fahr. Thus the observed transpiration times 
of a mixture of equal volumes of hydrogen and carbonic oxide at 60° and 347°, were 
0’8870 and 0*8853 ; the transpiration times of air observed at the same temperatures 
being taken as unity. The transpiration times of a mixture of equal volumes of 
hydrogen and nitrogen, referred to the times of air in the same manner, were at 65°, 
0-8939 ; at 347°, 0*8924 ; again, at64°*5, 0*8930 ; and at 347°, 0*8872. The transpira- 
tion ratios are thus as nearly as possible constant at these widely distant tempera- 
tures. 
The transpiration times of air and hydrogen alone, at 203°, were found on two dif- 
ferent occasions as 1 to 0*4841, and 1 to 0*4880. Multiplying these hydrogen times 
by 0*9 to bring them to the scale of oxygen, we have for the transpiration times of 
