519 



when dry 7| lbs. 



8| 



I cannot depend on the dry weight, nor draw any conclu- 

 sions from it, though it follows nearly the same proportion as 

 the fresh grass ; the weather had been very wet, and it had 

 been left too long exposed to it. 



The great advantage of the plot manured with the prus- 

 siate of potash over the others is very remarkable ; for about 

 a month it seemed rather inferior to that manured with the 

 muriate of ammonia ; but after that time the difference be- 

 came very perceptible to the eye or foot. 



The final advantage of No. 4 above No. I is at the rate of 

 38 cwt. of fresh grass, or 8| cwt. of dry grass to the acre. 

 The reason of this superiority cannot arise from the nitrogen 

 alone, as the quantity of it in the three ounces of muriate of 

 ammonia (applied to No. I) actually exceeds that in the three 

 ounces of ferro-cyanuret of potassium, in the proportion of 

 13 to 1 1. It must, therefore, be sought for in the other ele- 

 ments of the salt. 



Supposing this salt to be absorbed by the plant, and 

 decomposed in the same manner as the ammoniacal salts, 

 the plant will then obtain carbon and potash, as well as the 

 nitrogen, in the nascent state, which seems to be the only 

 way in which carbon can be assimilated. In fact almost every 

 element required by the plant is contained in this one com- 

 pound, and obtained by one and the same decomposition. 



I beg leave to lay these facts before the Academy, as they 

 may prove interesting to those engaged in the subject of 

 manures, and may tend to throw a little further light on the 

 subject of the food of plants, should they be confirmed on repe- 

 tition ; but I fear they can be of no service to the practical agri- 



