PHYSICAL CIIARACTKUS OF THE SOIL. 160 



is iibijorbeil by })orous bodies in the largest quantity. 

 This not only displaces otlier gases from their adhesion to 

 solid surfaces, but by its own attractions modifies these 

 adhesions. 



Reichardt and Blumtritt take no account of water-gas, 

 except in the few experiments where the substances were 

 purposely moistened. In all their trials, however, moist- 

 ure was present, and liad its quantity been estimated, 

 doubtless its influence on the extent and kind of absorp- 

 tion would have been strikingly evident throughout. 



Ammonia and carbonate of ammonia in the gaseous 

 form are absorbed from the air by the dry soil, to a less 

 degree than by a soil that is moist, as will be noticed fully 

 hereafter. 



Chemical Action induced by Adhesion. — This physical 



property often leads to remarkable chemical effects ; in 

 other words, adhesion exalts or brings into play the force 

 of affinity. When charcoal absorbs those emanations 

 from putrefying animal matters which we scarcely know, 

 save by their intolerable odor and poisonous influence, it 

 causes at the same time their rapid and complete oxida- 

 tion ; and hence a j^iece of tainted meat is sweetened by 

 covering it with a thin layer of powdered charcoal. As 

 Stenhouse has shown, the carcass of a small animal may 

 be kept in a living-room during the hottest weather with- 

 out giving off any putrid odor, provided it be surrounded 

 on all sides by a layer of powdered charcoal an inch or 

 more thick. Thus circumstanced, it simply smells of am- 

 monia, and its destructible parts are resolved directly in- 

 to water, carbonic acid, free nitrogen, and ammonia, pre- 

 cisely as if they were burned in a furnace, and without 

 the appearance of any of the effluvium that ordinarily 

 arises from decaying flesh. 



The metal platinum exhibits a remarkable condensing 

 power, which is manifest even with the ])olished surf ice of 

 foil or wire : but is most striking when the metal is 



