452 Action of the Atmosphere upon 77eiuli/- deepened Soil. 



ferruginous earths that frequently abound in some subsoils will^ 

 however, on exposure to the atmosphere, take up ammonia to a 

 considerable degree after they have crumbled down under the 

 influences of frost, rains, and drought. 



This power of drawing in the ammonia is so important and 

 interesting, now when that substance has been demonstrated to 

 be always present in the air, that some farther consideration of 

 it seems here necessary. It has been seen that ammonia is 

 taken up by porous bodies, and by water, to an extent greatly 

 exceeding the other gase? ; it may therefore be expected that the 

 soil will likely be able to condense a considerable quantity of 

 it within its pores, for ammonia, being a highly condensible gas, 

 is absorbed by solid bodies in much larger proportions than air or 

 oxygen. 



Faraday made some interesting researches on this subject 

 owing to certain remarkable statements made by Ileiset, who 

 had obtained ammonia from substances which were quite desti- 

 tute of nitrogen, and who had assumed that the nitrogen of the 

 air contained in their pores was the source of this formation of 

 ammonia. 



Faraday found that white clay from Cornwall, after being 

 heated to redness and exposed for a week to the air, yielded 

 ammonia abundantly when heated in a tube ; and that sea-sand 

 heated to redness in a crucible and allowed to cool on a plate of 

 copper, on being afterwards sliaken upon the hand and stirred 

 about there for a few moments with the fingers, was found to 

 contain ammonia in very appreciable quantity. Some asbestus, 

 in like manner, heated to redness and afterwards simply pressed 

 with the finger, yielded indications of ammonia when heated in 

 a tube. Faraday also ascertained that fused potash had the 

 power of absorbing ammonia from the air ; and, in short, that 

 the strange results of Reiset arose from this overlooked property 

 of many bodies greedily absorbing ammonia from the atmospliere. " 

 (Quarferli/ Journal of Science, vol. xix.) 



Bonis sliowed that the peculiar odour observed on moistening 

 minerals containing alumina is partly owing to their exhaling 

 ammonia. Boussingault states that the ferruginous earths in the 

 primitive rocks of South America yield ammonia on being 

 heated, and Rerzelius found the same to be the case in those of 

 Sweden; and Braconnot has shown that most basalts, trap, 

 granite, syenite, hornblende rock, and many other minerals, 

 yield by dry distillation water containing a sensible quantity of 

 ammonia. Soils, therefore, derived from such minerals will 

 absorb a good deal of ammonia, even although they do not contain 

 much organic matter. 



Whinstone, wliich is a Scotch term for greenstone and other 



