PROPERTIES OF MATTER EST THE GASEOUS STATE. 765 
Table XVI.—Time of transpiration of equal volumes of air at different pressures 
through meerschaum plate No. 2. 
Initial 
pressure. 
Time of 
transpiration in 
seconds. 
Log of pressure. 
Log of time. 
inches. 
30- 
374 
T477 
2-8286 
15T0 
716 
1-179 
2-8549 
12"75 
720 
1-105 
2-8573 
11-25 
724 
1-051 
2-8579 
6-40 
725 
1-806 
2-8600 
0-00 
725 
1-792 
2-8603 
Table XVII.—Time of transpiration of equal volumes of hydrogen at different 
pressures through meerschaum plate No. 3. 
Initial 
pressure. 
Time of 
transpiration in Log of pressure, 
seconds. 
Log of time. 
inches. 
32-5 
187 
1-5118 
2-27184 
13-25 
198 
1-1222 
2-29665 
12-40 
198 
1-0934 
2-29666 
4-05 
200 
1-6074 
2-30103 
3-85 
200 
1 5854 
2-30103 
From these tables it appears that the transpiration times at pressures nearly equal 
to that of the atmosphere are for air and hydrogen, through stucco, as 55 to 19, as 2\9 
to 1, while through meerschaum they are as 3'6 to 1. 
Graham found the ratio for stucco 2‘8 to 1, and for graphite 3 - 8 to 1. 
The small difference between these numbers may be well explained by supposing, as 
is quite probable, that the stucco used by Graham was rather coarser than plate 
No. 2, also that the graphite was finer than the meerschaum ; but even allowing the 
difference, the present results are in very fair accord with Graham’s as far as the 
conditions of pressure corresponded. 
When, however, we come to compare the times for air and hydrogen at lower 
pressures, we see that not only does this ratio differ very greatly from that obtained 
by Graham for stucco, but that it approaches what he obtained with graphite. Thus 
at a pressure of 4 inches the ratio of the times are as 96 to 27, as 3’56 to 1, or they 
are the same as with the meerschaum at the pressure of the atmosphere. For lower 
pressures we have indications of a still higher ratio. Thus at 1 inch the ratio is 103 
to 28‘5, or 3'62 to 1. 
In the same way we see that with the meerschaum as the pressure falls we have an 
increase in the difference of the times for air and hydrogen. 
