80 THE MASSACHUSETTS SOCIETY 



their thoughts and their pens on the various operations in agricul- 

 ture; yet diversities of opinion still exist, and the reasons of many of 

 those operations have been little more than conjectural. What con- 

 stitutes the food of plants has long been a subject of diligent inquiry., 

 It was natural to suppose that if this food could be discovered, it 

 could more easily be provided, or at least more efficaciously adminis- 

 tered. The palpable differences which distinguish the immense 

 variety of plants in their forms, textures, colors and tastes, naturally 

 suggested the idea that each variety required its specific nourish- 

 ment. Yet, it being a matter of common observation that the same 

 soil would nourish and bring to maturity multitudes of different 

 plants, of very opposite qualities some yielding wholesome food and 

 others a deadly poison at the same time all growing together and 

 robbing one another, a nobler and more simple idea presented itself 

 that the food of all plants was the same, but that each species was 

 endued with the power of converting that food to its own peculiar 

 substance; as, among animals, the same grain, produced all the varie- 

 ties of flesh which go to sustain the life of man." 



Having thus stated the problem, the speaker proceeded to his solu- 

 tion, which may be given in his own words, omitting a few connect- 

 ing clauses : 



" By the modern discoveries in chemistry, these mysterious effects 

 seem to be accounted for. For it appears that all kinds of plants are 

 composed of a small number of elements, whose different arrange- 

 ments and combinations produce all the varieties in question. The 

 three principal ingredients in the food of plants, and which, by them 

 elaborated, constitute the food of man and other animals, are named 

 by chemists, carbon, oxygen and hydrogen; in;other words, charcoal, 

 vital air and inflammable air ; and these exist in the air we breathe as 

 well as in manures consisting of vegetable and animal matters. It 

 may seem incredible that the thin air, an invisible matter, should 

 be changed in the process of vegetation into solid substances, as 

 wood and stone. But nothing has been more clearly ascertained 

 than that in 100 parts of pure limestone, forty-five parts are fixed air 

 or carbonic acid. This, in the act of burning the stone into lime, is 

 expelled; for if at that time the stone be weighed it will be found to 

 have lost so much of its original weight. It is also well known that 

 this same lime, which, slaked with water or exposed to air, falls down 

 into a powder, will immediately afterwards begin to imbibe fixed air 

 or carbonic acid from the atmosphere, and eventually, though slowly, 

 recover its original weight." 



Having remarked that while the same food furnishes nourishment 

 to a variety of plants, he said it is also true that plants have prefer- 

 ences among the variety of soils, and that soils like plants consist of 

 different proportions of the same elements, and then adds : 



" Four earths generally abound in soils, and these by chemists are 

 called aluminous, siliceous, calcareous and magnesian ; and of these 

 the three first are the principal, and, in familiar language, well known 

 to every farmer as clay, sand and lime. Calcareous earth is consid- 

 ered as essential to give to soils the capacity of attaining to the 

 highest degree of fertility. Few soils, indeed, are wholly destitute 

 of calcareous matter, but very few possess so large a proportion of it 

 as would be salutary. Limestone is the great source of calcareous 

 matter. But this is of various qualities. To know, then, the consti- 

 tution of the lime he uses is important to the farmer." 



Pursuing the chemical problem a little farther, the speaker quoted 

 Sir Humphrey Davy's explanation of manner in which lime acts upon 



