AT WHICH A SUBSTANCE IS APPLIED. 61 



which has been made with the view of throwing light upon this 

 point, was performed in 1847 by Mr Alexander Main, at White- 

 hill in Mid-Lothian, and their results have been published in the 

 Transactions of the Highland Society for March 1849, p. 530. 

 He applied Peruvian guano, African guano, and saltpetre refuse,* 

 in equal quantities of two cwt. per acre, to different portions of 

 the same crop of Taunton-Dean wheat. To three portions the 

 substances were applied on the 1st of February, and to three 

 others on the 30th of April, with the following results per im- 

 perial acre : 



APPLIED IST FEBRUARY. APPLIED 30TH APRIL. 

 Grain. Straw. Grain. Straw. 



No application, . 27^ bush. 19^ cwt. ... 



Peruvian guano, 2 cwt. 29^ ... 24 ... 29 bush. 28 cwt. 



African guano, 2 cwt. 27 J ... 24 ... 27 ... 27^ ... 



Saltpetre refuse, 2 cwL 27^ ... 26 J ... 33^ ... 31 ... 



In regard to the guanos, it does not appear from these expe- 

 riments that the delay of three months had any other effect than 

 slightly to increase the growth of straw. Where straw is usually 

 short, therefore, a later application of guano is suggested by 

 these results. 



As to the saltpetre refuse, an increase of six bushels of grain, 

 as well as four cwt. of straw, seems to imply that in the soil 

 and locality of Whitehill a later application of this substance is 

 likely to be the more profitable. 



At the same time, I am forced to regret that the absence of 

 duplicate comparative experiments renders these results un- 

 worthy of that reliance which we must be able to place on all 

 experiments by which the farmer is likely to be induced to ex- 

 pend his money, or the scientific agriculturist to draw theoretical 

 conclusions. I am glad to learn from Mr Main's paper that he 

 intends to prosecute this point in future years ; and I hope he 

 will do it so methodically, and with so much care to eliminate 

 the effect of natural or acquired differences in the soil, that his 

 new results shall prove undoubted accessions to our knowledge. 



b Should all the manure be applied at one time f Many 

 practical men find it better, in preparing their land for turnips, 



* The saline matter left when the crude saltpetre of commerce is dissolved 

 and re-crystallised for the use of the powder manufactories. 



