TO THE FARMER. 13 



Let US recall to remembrance the lengthy prescrip- 

 tions and enormous quantity of medicine formerly 

 enjoined by the physician, when compared with the 

 practice of the present day; how short and simple, 

 in like manner, have the formulas and recipes be- 

 come, by which the printer prepares his ink, the dyer 

 his dye, the joiner his varnish! What is the reason 

 of this change ? Is it not that a better insight into 

 chemistry has demonstrated the exact value and 

 mode of action of each specific ingredient, in these 

 recipes, and made it possible to separate the ineffica- 

 cious from the truly efficacious element ? whereas, 

 so long as the principle, that, if one answered no 

 good purpose, another might, remained in vogue, 

 doubts were necessarily felt as to the expediency of 

 attempting any alteration, from the apprehension 

 that in so doing the best ingredient of the com- 

 pound might peradventure be removed. — Has agri- 

 culture in this respect attained to clear and distinct 

 principles ? In no wise. Let us but read, not in- 

 deed books upon agricultural chemistry, but the 

 writings of practical agriculturists themselves ; are 

 they agreed upon the modus operandi and the man- 

 ner of applying the simplest manures, lime, gypsum, 

 humus, ammonia, rock-salt, etc. ? By no means. 

 Yet how can trustworthy precepts be laid down for 

 the method of employing these substances as ma- 

 nures, if no clear notions are entertained respecting 

 their influence upon the soil and upon plants ? 



Thirty or forty years ago phosphoric match-boxes 

 2 



