228 QUARTERLY JOURNAL 





tation of crops. Now a very important question arises, and it is 

 this : Ought we not to increase the fertility of our farms very fast, 

 when it is considered that the larger part of the nutriment of plants 

 is derived from the atmosphere ? That for every pound of food they- 

 use of our furnishing, they restore to us three, four, or five pounds 

 more derived from another source, would call for an affirmative an- 

 swer. As it is well determined that our gain is great, it remains for 

 us to discover the cause of loss, and the preventive too, for lose we 

 certainly must, else : for every load of manure we feed to plants, 

 we ought at the period of its exhaustion to have six times as much 

 on hand, provided the produce is all made use of on the farm, and 

 five-sixths is the amount gained. 



I am satisfied that a great deal more than half the support of 

 plants is derived from some other source than the product of decayed 

 vegetable matter in the soil itself, from the fact that grain farms are | ^ 

 often made to improve rapidly, from the resources of liie farm 

 which are left after selling off the grain, which is the most valuable 

 portion for manure, and after losing a great part of the strength of I 

 the manure which is made on the farm by the escape of its gases i 

 and salts, for the want, in part, of some substances to combine and 

 retain them for the use of plants. 



Again, meadow land can be cropped, and not manured save and 

 except with plaster, and the soil improve meantime (and I even 

 think the same result may be experienced without the use of plaster, 

 but in a less degree of rapidity), as I have shown in a former article. 

 I know that such has been the result where plaster was used. In 

 an improvement of a soil almost destitute of mould, in this way, 

 admitting that it is to be attributed to the use of plaster, there is an 

 great increase of mould, which I suppose is principally carbon ; but 

 the plaster did not contain carbon. It must operate then by pro- 

 moting the growth of vegetation that does, which must derive it from 

 the atmosphere ; and the operation of the plaster must be by its f 

 sulphuric acid combining the ammonia of the atmosphere. I am 

 aware that Dr. Dana attributed its good effects to another causeji 

 viz. the sulphuric acid of the plaster dissolving the silex or gritty 

 matter of the soil, and thus setting free the alkalies contained there- 

 in; which in turn dissolve more silex, and thus set free another portion 

 of alkali, and so on. But, in my view, the great effects produced 

 from the use of a little plaster must be attributed to another cause. 



