On the Use of Saltpetre as Manure. 



277 



and the protection it had afforded during the winter, caused 

 the clover thus manured to be very rank and forward in growth, 

 and far superior to the unmanured part, which hooked weak and 

 bare. I however waited till the clover had just begun to grow, 

 and then, after having reduced the saltpetre to a fine powder, 

 it was sown by hand on the land left for that purpose. In 

 about a fortnight from that time I went to examine it, and could 

 see distinctly where the saltpetre had been used : it already sur- 

 passed the part manured with horse-dung in the breadth of its 

 leaves, and richness of its colour, which was changed to a very 

 dark green, and it continued through the season to grow with a 

 luxuriance of vegetation that produced a very large crop of clover, 

 quite equal, if not superior, to that of the horse manure ; nor could 

 we distinguish any difference in the value in the succeeding crop of 

 wheat. The saltpetre was used at the rate of 1 cwt. per acre ; 

 cost, 26s. 6d. in London ; carriage and sowing included, abvout 

 29s. per acre. The horse manure from the farm-yard, 10 loads, 

 or 25 yards, at 4.s. per yard ; cartage, 10s. ; spreading, 2s. ; making 

 a total of 51. 12s. per acre. The expence would have been much 

 increased had not the field been near the farm. The trial was on 

 sandy land of moderate quality. I could add a great number 

 more experiments, which would be but a repetition of the above, 

 and I have used it on spring corn with equal success. I also re- 

 commended it to a friend who tried it on oats, barley, and grass, 

 and a few weeks after the application I had an opportunity of in- 

 specting the crops, which were considerably higher and of a much 

 darker green where the saltpetre had been used than the other 

 parts of the fields, and were judged to contain from 8 to 12 

 bushels of corn more per acre. Its effects were equally striking 

 on the meadow. It was used at 1 cwt. per acre. 



Nitrate of potash, according to Thomson, consists of 



1 atom of Nitric Acid . , 6*75 

 1 atom of Potash . . . 6*00 



12-75 



Or (in 100 parts) Nitric Acid . 54 '34 parts. 

 Potash . . . . 45-66 



And it is said by Davy to contain 1 part of Azote, 6 of Oxygen, and 1 

 of Potassium. 



It would be presumption were I to venture an opinion on its 

 mode of operation, nor for our present purpose may it be neces- 

 sary ; a well- authenticated collection of practical facts are of more 

 service and better understood by agriculturists. It may be asked, 

 Do you use saltpetre now ? to which I answer. Yes, and, while I 



