54 MASSACHUSETTS AGRICULTURE. 



the elements of putrefaction into the aliments of health and 

 growth. The theory of combustion, placed by experiment 

 beyond all controversy, has* disclosed new and important bear- 

 ings, which heat has in the economy of life and health and 

 growth, and its agencies in the changes and mutations, which 

 the earth's surface and all things on it, arc constantly under- 

 going, how and why it keeps the living organs together, how 

 and why it dissolves them. 



The geologist says — and those who lived before he had a 

 name never controverted it — that the basis of the soil is 

 mineral, made of rocks, (which he has described and named,) 

 crumbled by the incessant activity of heat, moisture, frost, and 

 other penetrative agents around and within them. Although 

 these operations may not have been detected, their effects were 

 known, as long ago as soils were divided into calcareous, sandy 

 and clayey, as lime, sand or clay, happened to prevail, and in 

 the like exposures and climates, the bearings of the various 

 proportions in their mechanical mixtures, upon the production 

 of the different grains, were known ; still they were looked upon 

 as an anchor-ground of the roots rather than as subserving other 

 purposes, and aside from improving physical texture, the parts 

 they took in the processes of vegetation, were ill conceived, if at 

 all understood. That they entered into the composition of vege- 

 table structure and became parts of the living tissues, would 

 have been thought a strange perversion of the nature of things. 

 Analysis, however, has detected in herbs most of the minerals 

 in the soil on which they grow. They polish the corn-stalk ; 

 stiffen and gloss the wheat-stem ; incrust and glaze the cane. 

 That their presence hastened development and maturity was 

 well known. How it was done was a matter of speculation. 

 They arc spoken of in old treatises as stimulants to the roots, 

 and starting into activity dormant fertilizers — rarely as the 

 proper food of plants. 



Now plaster of Paris operates is a topic which has been 

 earnestly and learnedly discussed within the memory of all of 

 us. The better opinion seemed to be that it drew moisture 

 from the air, and acted as a condiment in preparing nutritious 

 matters and exciting vegetation. That it may thus act is not 

 unlikely. Nature in her economy uses the same thing in 

 various ways and for various ends. The problem, however, 



