144 



The Royal Agricultural Society say that Chemistry is 

 unable to explain the productiveness of soils. But why is she 

 unable ? One reason is, that, supposing every thing required 

 by the plant to be present in the soil, yet, if the soil be either 

 too wet or too dry, too cohesive or too loose, the plant will 

 not flourish ; and Chemical analysis does not declare this ; 

 for it affords no information respecting the mechanical divi- 

 sion in which substances exist in the soil. Again, the Chemi- 

 cal analysis of soils, to be worth any thing, must be conducted 

 with more rigid accuracy than those published by English 

 writers : to detect one cwt. of gypsum in an acre, there 

 would be only one quarter of a grain in a lb. of soil, or in 100 

 grains, only three and a half thousands of a grain (loVoo or 

 .00035 grains) : or, to discover if sufficient alumina existed 

 in a field for the production of red clover, there must be 

 ascertained if it contained .00001 per cent, (one hundred 

 thousandth.) The analyses, even by Sprengel, do not afford 

 us the quantity of nitrogen in each soil, or the capacity of 

 the soil for this substance, while it is well known that most 

 manures, as well as the different kinds of food, are valuable 

 in proportion to the quantity contained in them ; and it is 

 highly probable, cceteris paribus^ that the quantity of nitrogen 

 found existing in a soil, and the capacity of the soil for con- 

 taining that substance, would afford an easy indication of its 

 immediate fertility, and also of its requiring great or small 

 quantities of nitrogenous manures in its future cultivation.* 



Chemistry, however, outsteps her province when it at- 

 tempts to explain how vegetable productions are formed in 

 the plant by Chemical forces : for the recent discoveries of 

 Schwann, Henle, and Schleiden, prove that all the functions 

 of the plant are performed by the means of simple vesicles 

 and cells — that absorption, assimilation, fixation of carbon 

 from the atmosphere, respiration, exhalation, secretion, and 



* The celebrated Black Earth of Russia contains 2.45 per cent, of nitrogen. 



