188 APPENDIX. [March, 



Lowell, March 28, 1840. 

 Dear Sir, — 



The results referred to in your letter, are opposed to the common 

 opinion. Common opinion, especially in agriculture, is not always 

 founded on observation. It is oftener prejudice, than opinion ; and, 

 when inconsistent with well known facts, has not its source in obser- 

 vation or experiment. The whole resolves itself into this, dry plants 

 GIVE MORE GEiNE THAN GREEN. This follows from the little we know 

 of the process termed "fermentation;" I use the term as commonly 

 expressive of the spontaneous decay of vegetables. It includes the 

 three stacres of vinous, acid, and putrefactive fermentation. These 

 are not necessarily dependant, following in regular progression. They 

 are not cause and effect. Putrefaction may commence first, and it is 

 so different from the other two, in all its stages and products, that the 

 term " fermentation" ought never to have been applied to it. The 

 greater part of vegetables are susceptible of putrefaction only, a small 

 number become acid at once, and a still smaller number ever under- 

 go vinous, acetous, and putrefactive fermentation. Fermentation 

 then, in its widest sense, will help us to understand how dry crops may 

 be better manures than green. Let us glance at the principles and 

 products of fermentation. 



1st. What vegetable substances are susceptible of the vinous fer- 

 mentation, and what are its products? 



The juices only which contain sugar, or starch, convertible first into 

 gum and then into sugar by the action of azolizc'd vegetable principles, 

 especially gluten. Pure sugar never ferments. The vinous fermenta- 

 tion must be excited by some substance containing nitrogen. There 

 are three things essential to vinous fermentation, air or oxygen oras, 

 moisture in due proportion, and a temperature never below 50° F., nor 

 above 86° F. The products of this process are gases, ferment or 

 yeast, and vinous liquor. The gases are carbonic acid, and hydrogen. 

 The yeast proceeds from a change in the organization of the gluten 

 and albumen ; some late French experimenters think it proceeds from 

 a continued evolution of infusorial plants, hence yeast begets yeast, 

 like sowing crops of seed. However, let us leave speculation. The 

 main facts are as above stated. If, then, we plough in green plants, we 

 put them in a temperature favorable to the commencement of vinous 

 fermentation ; we bury them full of sap — the requisite moisture for vi- 

 nous fcrinciit^lion ; — we cover thera, whilst their saccharine principle 



