Laws of Absorption of Liquids by Porous Substances. 638 
these respects the law of filtration is analogous to that of absorp- 
tion; at the same time it must be observed that the relative ab- 
sorbent power of a substance does not always correspond to its 
filtermg power. 
The filters used in the following experiment belong to the 
second class of filters. 
Experiment XXII. 
The filter used in this experiment was thick unsized paper, and 
the liquid was spring water. The diameter of the orifice of the 
plate was ;4,ths of aninch. The filter-tube was the same as that 
of Experiment XVI. At the commencement of the experiment 
the liquid stood at the eighth division of the tube measured from 
the filter. The temperature was 64° throughout the experiment. 
| Value of v 
Descent of | C . time} Velocity per | 
the liquid, ‘a keconds, | cco | yy foreuala 
Ss. | v. ara 
0 0 Bo 30 
1 20 
I 97 1 12 1 7) 8 
1i 125 
2 225 140 TAG 
21 260 
3 400 FOO T5D 
34 450 
4 620 Eo DED 
41 685 
5 870 os ahs 
BL 960 
6 1360 Eo 49a 
62 1480 | 
7 1990 giv sto 
72 2160 | 
The formula expressing the relation between the time T and 
space S of descent is 
A G2"3 (185 bey tell eid in 5 Vo hie Gal) 
It will be seen how very nearly the velocity of descent of the 
liquid is represented by the formula v= - .1:3557°; showing 
that af the spaces of descent be taken in arithmetical progression, 
the corresponding velocities of descent will be in geometrical pro- 
gression. ‘Vhe common ratio of the velocities in this experiment 
=: 
eo 355 
The relation of T and S for both kinds of filters may be repre- 
