2J^ QUARTERLYJOURNAL. 



" In order to form a conception of the effect of gypsum it may 

 be sufficient to remark that 110 pounds of burned gypsum fixes 

 as much ammonia in the soil, as 6,880 pounds of horse's urine could 

 yield to it, even in the supposition that all the nitrogen of the 

 urea and hippurci acid were absorbed by the plants, without the 

 smallest loss in the form of carbonate of ammonia. If we admit 

 with Boussingault, that the nitrogen in grasses amounts to -j-i^ of 

 its weight, then every pound of nitrogen which we add increases 

 the produce of the meadow 100 pounds, and this increased product 

 of 100 pounds is effected by the aid of a little more than four 

 pounds of gypsum. 



INORGANIC CONSTITUENTS OF PLANTS. 



All the organic parts of plants are formed by means of transfor- 

 mations which take place in the substances I have named, to wit, 

 water, carbonic acid and ammonia, or nitric acid. But there are 

 other constituents which also require notice. 



In all plants there is a certain amount of mineral substances 

 which remain after burning, in the shape of ashes. These substan- 

 ces vary in different plants, and are more abundant in some than 

 in others. They consist, for the most part, of salts of soda and 

 potash, silex, alumina, lime, magnesia and some others. 



Liebig has insisted very strongly on the necessity of these 

 mineral ingredients for plants, and has shown that no matter how 

 abundantly a plant may be supplied with water, carbonic acid, 

 and nitrogen, it will not flourish if the inorganic constituents are 

 wanting. Thus wheat, rye, peas and beans, contain a large pro- 

 portion of the alkaline and earthy phosphates, and will not flourish 

 in a soil destitute of them, however rich it may be in other ingre- 

 dients. 



The inorganic constituents are originally derived from the 

 disentegration and decomposition of the rocks which form the basis 

 of the soil, and that portion of them which is removed with the 

 crops must be restored in the shape of manures, or by allowing 

 the ground to lie fallow while a new supply is generated by the 

 further disintegration of the rock. 



When lands are exhausted by successive crops, the exhaustion 

 depends rather on the absence of the inorganic constituents than of 

 the sources of carbonic acid and water. This exhaustion of the 

 soil may be prevented to some extent, by raising successively crops 



