66 EXPERIMENTS UPON POTATOES. [AppeTuHx, 



tained in a few words, thrust in as it were, among the remarks appended to the 

 table (1°, p. 49.) In the later printed copies I have caused them to be put in 

 italics, with the view of bringing them into notice. If the reader will turn to p. 

 20 of this Appendix, he will find a remarkable experiment recorded, in which, 

 by top-dressuig well-manured potatoes, with a mixture of ^ of nitrate and | of 

 sulphate of soda, the enormous crop of 30 tons an acre was obtained from the 

 small plot experimented upon. Some of these potatoes were kept for seed, and 

 planted alongside of others of the same variety, which had not been so dressed, 

 and tlie result is stated in the few words above referred to — " These last, v.nder 

 the same treatment in every respect, did not produce so good a crop by 15 boUs (3| 

 tons^ per acre" 



In so far, therefore, as this experiment is tc be relied upon — for we must not 

 be hasty in drawing general conclusions — it appears that the benefit to be de- 

 rived from a skilful treatment of the potato plant does not terminate with the 

 greater immediate crop we reap, but extends also into future years, improving 

 the seed and rendering its after-culture more productive. 



Suggestion VII. — This idea is worth pursuing, were it only for the purpose 

 of making out the possible existence of so important a physiological law — how 

 much more when it appears so pregnant with important practical results. But 

 thus it is in all cases, that the prosecution of experimental research, with im- 

 mediate reference either to purely scientific or to purely practical results, ends 

 in improving and benefitting both abstract science and economical practice. 



I am unwilling to follow out or to reason upon this possible law, as if it 

 were really established ; but the possibility of its tmth appears to throw light 

 upon such questions as this — why the seed must occasionally be changed if 

 large crops are to be continually reaped. One soil may be adapted to give the 

 plant a large supply of this or that substance in which the other soil is com- 

 paratively deficient ; audit maybe possible to medicate our seed-corn, while 

 growing, so as to give it the qualities which at present it can acquire only by a 

 change of soil. 



All this, however, can be only determined by experiment, and the intelligent 

 reader will net fail to be stmck with the remarkable richness.of these fii-st trials, 

 in suggestions for future carefully conducted experimental researches. 



5°. How should saViTie manures be applied to the potato crop? — Ought they to 

 be mixed with the manure, or to be applied as a top-dressing % Mr. Fleming's 

 experiments do rtot fully solve this question ; because the soil on his two fields 

 was very unlike in quality. Thus with manure alone the one field produced 

 12 tons 15 cwt., the other only 8 tons 17 cwt per acre. A perfectly satisfactory 

 solution of the question can be obtained only by experiments with the same sub- 

 stances, upon the same soil, and with the same variety of potato. Yet the experi- 

 ments now before us add considerably to our knowledge vipon this point, and 

 such of them as are capable of being compared together are much in favour 

 of mixing the saline substances with the 7namire. Thus apphed in nearly 

 equal proportions by both methods, nitrate of soda, sulphate of magnesia, and 

 sulphate of ammonia, gave the following results : — 



FIRST FIELD. SECOND PIEIiD, 



Top-dressed. Mixed with manure, 

 tons. cwt. tons, cwt 



Manure alone 12 15 8 17 



Nitrate of soda 1(5 12 7 



Sulphate of magnesia .... 13 5 117 



Sulphate of ammonia .... 14 10 13 7 



The proportionate increase, therefore, in these three cases, is greatly in favour 

 of mixing with the manure, but something may depend upon the soil and 

 season ; and, therefore, other experiments are necessary before we can draw a 

 genered conclusion. It may prove that some act better when applied in the one 

 >yay, and some in the other. 



6°. Sulphate of soda. — With this substance applied in either way, the tingu- 



