355 



failed contains only half the quantity we find in the other ; 

 this small quantity, however, amounts to more than 56 lbs. 

 per acre, which is more than double the amount required for 

 a crop of clover. The reason we always find so small a 

 quantity in the surface soil arises from its solubility in water; 

 portions are carried down by every shower, and fresh portions 

 are brought up, dissolved in water, from below, by capillary 

 attraction during summer ; this quantity, therefore, would be 

 considerably increased in dry weather, and would at all times, 

 except in very wet seasons, be amply sufiicient to supply 

 plants with the requisite amount of sulphur. There are other 

 facts, also, of a much more conclusive character, which prove 

 beyond doubt the fallacy of the statement that a deficiency 

 of gypsum is the cause of the failure of the red clover crop. 

 There are other plants which flourish on the same land, and 

 at the same time that red clover dies, and which contain con- 

 siderably more sulphur than it. I would instance Italian rye 

 grass, which analysis shows to contain .320 of sulphur, which 

 is equal to about 7 lbs. of sulphur, or 38 lbs. of gypsum, per 

 ton ; now this is not a plant which dies away as red clover 

 does, but flourishes at the very time : the wild mustard, or 

 ketlock, too, containing nearly double this quantity of sulphur, 

 grows luxuriantly on most soils where red clover fails. Even 

 white clover contains more sulphur than red^ and is not liable 

 to die away ; we may consequently conclude, contrary to the 

 old opinion, that the failure of the crop is not owing to a de- 

 ficiency of gypsum, for if such was the case, plants requiring 

 most gypsum would certainly die first. 



Lime and magnesia appear to answer similar purposes in 

 the organism of plants, and may probably replace each other 

 in combination. We find considerable quantities of these 

 earths in the ashes of red clover, particularly the former, 

 whichy during the burning, is converted into a sulphate and 

 phosphate. This lime may either be taken up as a sulphate 



