PoLYTPCHNic Association Proceedings. 



587 



as much sulphate of ammonia as will contain twenty-two and a 

 half pounds of ammonia, and if introduced without loss into the 

 interior of plants, this sulphate will furnish them with eighteen 

 and a half pounds of nitrogen. 



In the first volume of the British Husbandry, pages 322, 323, 

 the following experiment is recorded: 



Mr. Smith, of Tunstal, top-dressed one portion of a field of red 

 clover with powdered gypsum, at the rate of five bushels (or four 

 hundred weight) per acre, and compared the produce with another 

 portion of the same field, to which no manure had been applied. 

 The first crop was cut for hay, and the second ripened for seed* 

 The following were the comparative results per acre: 



The excess of produce in all the crops upon the gypsumed land 

 is ver}^ large. By the result of Boussingault's analysis, dry clover 

 seed contains seven per cent, and the hay of red clover one and a 

 half per cent of nitrogen. 



The seed, as it was weighed by Mr. Smith, would still contain 

 one-ninth its weight of water, and consequently only six and a 

 third per cent of nitrogen. 



Let it be taken at six per cent, and let the straio be supposed 

 to contain only one per cent of nitrogen — the quantity of this 

 element being found to diminish in the granes after the seed has 

 ripened, and to average one per cent in the straw of wheat, oats 

 and barley — the weight of nitrogen reaped in the whole crop 

 would then be as follows: 



Forty hundred weight hay (4,480 pounds), at one and a 



half per cent of nitrogen, contain 67 pounds. 



Eighty-five pounds seed, at six per cent, contain 5 do 



Seventeen hundred weight, three quarters, twelve pounds 

 (2,000 pounds) straw, at one per cent 20 do 



Total nitrogen in excess of crop 92 do 



