No VIIl.] EXPERIMENTS UPON TURNIPS. 61 



mainly brought about by the expression of scientific opinion, and by the readi- 

 ness with which various persons, manure-manufacturers and others, have put 

 in practice the suggestions contained in the preceding part of this Appendix 

 (p. 26), for the formation of an artificial mixture in imitation of the natural 

 guano. The fear of competition produced its natural effect upon the market, 

 and led the importers of this substance to content themselves with a smaller 

 profit. It is to be hoped that the more extended sale which has followed the 

 reduction, will leave the spirited merchants who first brought it into the country 

 no reason to regret the diminution in price. The benefits which the practical 

 agriculturist derives from one such reduction as this are not all at first 

 sight perceptible. The demand for guano has so greatly lessened the call for 

 rape-dust, that it has also fallen in price from £8 to £5 10s, per ton. Thus 

 ramified and extended are the results of a single chemical investigation — or the 

 publication of a single well-founded scientific opinion. 



3*^. Artificial Chtano. — In connection with this subject it is important to as- 

 certain to what extent the attempts to manufacture a substitute for the natural 

 guano have been attended with success — in so far as the turnip crop is concern- 

 ed. The only comparative results which the above experiments present, are the 

 following — those upon Swedes being obtained by the use of o cwt. of each 

 mixture, those upon the yellow and white turnips by the use of 5 cwt. of each: — 



Swedes. Early Yellow. White Globe. 



1°. Nothing . . . 12 tons 5 cwt. 12 tons 17 cwt. — tons — cwt. 



2°. Natural guano . . 23 " 8 " 32 " 2 " 32 " 15 " 

 3°. Barochan artificial guano 17 " 14 « 24 " 2 " 22 " 10 " 

 4°. Turnbull's artificial guano 14 " 11 " 21 " 4 " — « _ «' 



These results show that, when equal quantities are employed, equal results 

 are not obtained from the natural guano and from the artificial mixtures. 

 It also appears that Mr. Fleming's mixture is much more efficacious than ths^ 

 of Mr. Turnbull. They are made up, with some modifications, after the recipk 

 given in the preceding part of this Appendix (p. 25), but are, no doubt, suscep- 

 tible of improvement. It is, indeed, one of the indirect benefits which will re- 

 sult from the introduction of this foreign manure, that it will stimulate to expe- 

 riments, by which we shall, no doubt, at last successfully imitate it — and wili 

 lead, at the same time, to a more general and thorough understanding of the 

 principles upon which mixed manures ought to be compounded, and of the 

 mode of preparing them with the greatest possible economy. Many crude mix- 

 tures may be made at first, by dealers in manure and others, and many instan- 

 ces of want of success may occur, but now that we have adopted the system of 

 recording results, whether apparently successful or the contrary, there is little fear 

 of our arriving at satisfactory and economical truths at last. 



Suggestion III. — In experiments made for the purpose of aiding the real ad- 

 vance of scientific agriculture, I would suggest that no mixture should be used of 

 which the composition is not exactly knowji — which, therefore, has not been either 

 made by the experimenter himself or by some dealer upon whose honor perfect 

 reliance is to be placed. The use of the random mixtures now sold under so 

 many different names, however successful they may be in this or that case, can 

 never lead to the discovery of useful agricultural principles, and, therefore, are 

 unworthy of the attention of the cultivator of inductive experimental agriculture. 



i°. Sulphate of ammonia. — These remarks lead me to notice the effect ascrib- 

 ed in Mr. Fleming's second table (p. 44), to sulphate of ammonia — one cwt. 

 of which nearly doubled the crop. Thus — 



The unmanured soil gave . . 12 tons 17 cwt. 

 With 1 cwt. of sulphate of ammonia 24 " 11 " 



l^his is exactly equal to the effect produced by 15 cwt. of rape-dust at a cost of 

 X(i iOs. But the sulphate of ammonia here employed was that prepared by 

 the Messrs. Turnbull, of Glasgow — which is not merely sulphate of ammonia, 

 but a variable and undetcrvmied mixture. It is prepared from urine, and I be- 



I 



