44 AMERICAN AGRICULTURE. 



gorous start to vegetables. This enables them rapidly to 

 push forward their roots, stems and leaves, thus obtaining a 

 greater range for the roots and more mouths for the leaves 

 to draw their nourishment from the atmosphere. 



CARBONATES, NITRATES, SULPHATES, PHOSPHATES, 

 SILICATES, AND CHLORIDES. 



Several of these have just been particularly enumerated. 

 The remainder are composed of carbonic, nitric, sulphuric 

 and phosphoric acids, silica and chlorine, in chemical com- 

 bination with potash, soda, lime and the other bases of 

 plants. Although no one of these can fail to benefit crops ? 

 when rightly applied, yet the expense of most of them will 

 prevent their extended use. This can only be looked for 

 from those which are procurable at a cheap rate. The che- 

 mical laboratories, glass works and some other manufacto- 

 ries, afford in their refuse materials, more or less of these 

 mineral manures, which would well repay the farmer for 

 removing and applying to his land. The most obvious that 

 occur in this country, are all that will be here mentioned. 



OLD PLASTER. 



This is a true silicate of lime, being formed mostly of sili- 

 ceous sand and lime, chemically combined. For meadows, 

 and for most other crops, especially on clays and loams, this 

 is worth twice its weight in hay ; as it will produce a large 

 growth of grass for years in succession, without other ma- 

 nure. This effect is due not only to the lime and sand, but to 

 the nitric acid which they have abstracted from the atmos- 

 phere, and which they continue alternately (while in com- 

 bination) to absorb from the air and give out to the growing 

 plant. But the farmer cannot too carefully remember, that 

 with this, as with all other saline manures, but a part of the 

 ingredients only is thus supplied to vegetables ; and without 

 the addition of the others, the soil will sooner or later become 

 exhausted. 



BROKEN BRICK AND BURNT CLAY. 



These are composed mostly of silicate of alumina, generally 

 mixed with silicate of potash and other substances. They 

 are of much value as a top-dressing for meadows. In addition 

 to their furnishing in themselves a minute quantity of the 

 food of plants, like old plaster, they serve a much more ex- 



