328 SALT, NITKATE OF SODA, SALTS OF AMMONIA, ETC. 



Amount of magnesia in 



Manured Manured 



Unmanurcd. with with sulphate 



gypsum. of magnesia. 



100 parts of ash of clover-hay 5'S7 5*47 5'27 



In the whole crop ,. 8-8 Ibs. 13'29 Ibs. 13'54'lbs. 



Yariations in the percentage proportions of potash, 

 lime, and magnesia, may be often observed in all those 

 plants in which, as in the case of tobacco, the vine, and 

 the clover plant, potash may be substituted for lime, 

 and vice versa. But in such cases the decrease of one 

 body is invariably attended by a corresponding increase 

 of the other. 



Now if gypsum has the property of effecting a dis- 

 tribution of the potash in the ground, and this is want- 

 ing in magnesia, more potash should be contained in 

 the clover manured with gypsum than with sulphate 

 of magnesia. According to the analysis made by 

 Pincus, the ash of the clover-hay contained : 



In per cent 



In the whole ash 



Clover Clover manured 



manured with with sulphate 



gypsum. of magnesia. 



Potash 35-37 Ibs. 32'91 Ibs. 



Lime 19'17 " 20-66 " 



Potash 85-9 " 84'6 " 



Lime 46-6 ' 53'2 " 



These figures show that the quantity of potash is 

 indeed larger, and that of lime smaller, in the crop 

 produced by manuring with sulphate of lime than in 

 the higher crop from sulphate of magnesia. 



In the clover-hay reaped from the latter plot, the 

 deficient potash was manifestly replaced by lime, and 

 in the clover-hay from the gypsum manure plot, a cer- 

 tain amount of lime by potash. 



An investigation, made with much carefulness, and 

 without the least bias, as this by Pincus, appears, 

 among the frivolous and loosely-conducted researches 

 with which agriculture unfortunately abounds, like a 

 green oasis in a dreary desert, and is well calculated 

 to show how much real knowledge remains still to be 

 gained of the processes in the soil with respect to the 

 nutrition of plants. (See ' Agriculturo-chemical and 



