Power of Soils to absorb Manure. 



125 



employed, the filtered liquid contained sulphate of lime ; when 

 muriates or nitrates of these alkalies were operated upon, muriate 

 or nitrate of lime was found in the place of the former salts. It 

 may be mentioned, also, in this place, that, at a later period of the 

 investigation, it was satisfactorily proved that the quantity of lime 

 acquired by the solution corresponded exactly to that of ammonia 

 removed from it — the action was therefore a true chemical decom- 

 position. These experiments were varied in many different ways 

 with results of more or less interest. It was found that the pro- 

 cess of filtration was by no means necessary ; by the mere mixing 

 of an alkaline solution with a proper quantity of soil, as by shak- 

 ing them together in a bottle and allowing the soil to subside, 

 the same result was obtained ; the action, therefore, was in no 

 way referrible to any physical law brought into operation by the 

 process of filtration. 



Again, it was found that the combination between the soil and 

 the alkaline substance was rapid, if not instantaneous, partaking 

 therefore of the nature of the ordinary union between an acid and 

 alkali. In the course of these experiments several different soils 

 were operated upon, and it was found that all soils capable of 

 profitable cultivation possessed the property in question in a 

 greater or less degree. It was shown that the power to absorb 

 alkaline substances did not exist in sand ; that the organic matters 

 of the soil had nothing to do with it ; that the addition of car- 

 bonate of Ume to a soil did not increase its absorptive power for 

 these salts ; and indeed that a soil in which carbonate of lime did 

 not occur, might still possess in a high degree the power of 

 removing ammonia or potash from solution, and it was evident 

 that the active ingredient in all these cases was clay. Further 

 trials proved that the stiffest and most tenacious clays taken 

 from considerable depths, which had never since their deposition 

 been exposed to atmospheric influences, and which also were 

 absolutely free from organic matter, or carbonate of lime, that 

 these pure clays possessed, to the fullest extent, the absorptive 

 property. By these experiments the subject was so far narrowed 

 that the origin of the power in question had. been traced to the 

 clay existing in all soils. It still, however, remained to be con- 

 sidered, whether the whole clay took an active part in these 

 changes, or whether there existed in clay some chemical com- 

 pound in small quantity to which the action was due. This 

 question was to be decided by the extent to which clay was able 

 to unite with ammonia, or other alkaline bases ; and it soon 

 became evident that the idea of the clay as a whole being the 

 cause of the absorptive property, was inconsistent with all the 

 ascertained laws of chemical combination. I shall here very 

 shortly refer to some of the experiments which were made to 



