GYPSUM. 



329 



The analyses here do not, indicate the modes in which the various 

 substances found were combined >" the ashes ; but supposing that 

 the whole of the sulphuric acid existed in combination with lime, 

 which it most probably did, the preceding results would meet us in 

 the following shape : the ashes of the clover grown upon soil with- 

 out gypsum contain 6.0 per cent, of sulphate of lime ; those of clover 

 grown upon a soil with gypsum, 5.7 per cent. 



As it is impossible to answer for so small a difference as Sj^^-^ 

 parts in researches of this kind, we must presume that the two ashes 

 contained the same proportions of sulphate of lime. 



Here, however, as in all other agricultural questions, isolated 

 analyses throw but little light on the subject of inquiry. In order 

 that they may enable us to arrive at any definite conclusion, two 

 new elements must be taken into the discussion : 1st. The propor- 

 tion of ash furnished by a given weight of the forage gathered ; 2d. 

 The quantity of forage yielded by a given surface before and after 

 the use of gypsum. 



I have taken from my own observations the quantity of dry forage 

 yielded by the two cuttings of 2d year's clover after gypsum, as 

 amounting to 41 cwt. per acre. The same surface in the 1st year, 

 and before the use of gypsum, would have produced but 9 cwt. 100 

 of dry clover gave : 



Year. Ashes. 



Clover ungypsed 1841 12.0 



Idem 1842 11.2 



Clover gypsed 1841 7.0 



Idem 1842 7.7 



Ashes freed from 



carbonic acid 



per ceut. 



10.3 

 8.8 

 5.4 

 3.6 



Per acre. 



103 lbs. 



89 " 



248 " 



257 " 



It is therefore obvious, that in the course of the three months 

 which followed the application of the gypsum, the soil must have 

 supplied the plant with very considerable quantities of mineral sub- 

 stance ; the crops taken from the gvpsed soils contained in fact two 



28* 



