On the Laws of Absorption of Liquids by Porous Substances. 365 



linen, &c, were prepared for experiment in the following man- 

 ner : after being cut to their desired widths, and in some cases 

 graduated, stout platinum wires were attached to their lower 

 extremities, to give them a uniform tension and to sink these ex- 

 tremities in the liquid ; they were then steeped in boiling distilled 

 water, and afterwards thoroughly dried by evaporation ; and im- 

 mediately before being used they were suspended for about an 

 hour in the atmosphere, saturated with the vapour of the liquid. 

 The ascent of the liquid was, for the most part, observed by 

 means of a cathetometer ; but in some cases the strip itself was 

 graduated. The space S, moved over by the liquid through the 

 pores of the absorbent, is the elevation of the liquid line on the 

 absorbent measured from the level of the surface of the liquid 

 in which the absorbent is immersed. This liquid line was some- 

 times best observed by transmitted light, at other times by re- 

 flected light. Plate IV. fig. 8 represents the apparatus which 

 was, for the most part, employed in these experiments : — 



A B a glass jar having a welt at the top ground smooth to 

 receive the ground brass plate CD; S a stuffing-box attached 

 to the plate, through which passes the stout wire F G, support- 

 ing the absorbent G K immersed in the liquid B K ; E a stopcock 

 communicating, when required, with the stopcock of an air-pump ; 

 LM a water-bath maintained (when required) at a constant tempe- 

 rature by means of a jet of steam. The sliding wire, F G, enables 

 us to raise or depress the absorbent as may be required ; and 

 the stopcock E and ground plate enable us to keep the absorbent 

 suspended in an atmosphere saturated with the vapour of the 

 liquid, or it may be in a vessel exhausted of air. The apparatus 

 was modified to suit peculiar circumstances. In experimenting 

 with such substances as turpentine, or with linseed oil, the vessel 

 A B was exhausted of air by means of the air-pump, and then 

 the external air was allowed to enter the vessel through a tube 

 filled with dry chloride of calcium. The absorbent having been 

 for some time suspended in this dry air, its lower extremity, K, 

 was immersed in the oil by depressing the sliding wire F G. 



Experiment I. 

 The liquid used in this experiment was water. The absorbent 

 was unsized paper, 2 inches in width, close in texture, and weigh- 

 ing '72 gr. per square inch. The temperature was 56° through- 

 out the experiment. 



The experimental value of the velocity of ascent, v, in the 

 third column, is found by dividing the increment of space *25 

 by the mean interval of time ; thus we find corresponding 

 •25 



toS=3 ^ = iTl5^^3) = , ° 83 - 



