FARMER'S ASSISTANT. 81 



esteemed of much less value, as a manure ; but, in this 

 Country, it is said to be most valuable. 



The magnesian limestone may be known, from that 

 which is purely calcareous, by the slowness of its solution 

 in acids; as, even the softest kind of it, is longer in dis- 

 solving than marble. Frequently it has, also, a chrystalized 

 tructure ; and sometimes small black dots may be seen 

 interspersed throughout the mass. 



Silex) or the earth of flints, is exhibited mostly in the 

 form of crystaline sand. . 



Mumine is the basis of clay, and serves to endue that 

 earth with the peculiar characteristic of coniracting in bulk, 

 when dried ; and of expanding again, when moistened. 



jinimal matter, in a decomposing state, must be princi- 

 pally the remains of the various insects, and other animals, 

 which have existed, and perished, in the earth, during the 

 lapse of ages. 



The presence of the remains of animal matter, in earths, 

 is ascertained by applying a strong heat to them; under 

 the operation of which they emit a smell similar to that of 

 feathers when burning, and leave a residue which is prin- 

 cipally carbonaceous matter, together with carbonic acid, 

 volatile alkali, and inflammable aeriform products. 



Vegetable matter, in a decomposing state, is much more 

 apparent in almost every part of the surface of the earth ; 

 but most so in rich moulds, and in new lands, where the 

 surface is usually more or less covered with it. It forms 

 the upper stratum of bog-meadows, and indeed the whole 

 mass, where they are not underlaid with marie. When it 

 undergoes the operation of a strong heat, the residue is 

 mostly ashes. 



The saline compounds found in earths, or soils, are but 

 rarely to be discovered, and are principally common salt 

 (muriate of soda) epsom salt (sulphate of magnesia) and 

 the salts chemically called muriate, and sulphate, of potash, 

 nitrate of lime, and the mild alkalies. 



Soils containing the least of any particular saline ingre- 

 dient, that forms a part of the food of plants, will probably 

 always be found most benefited by the implication of that 

 kind of salt, as a manure. 



The oxyde (rust) of iron is found in all earths, or soils; 

 but mostly in yellow and redish clays, and in sands of simi- 

 lar colors. It would seem that the colors of these earths 

 are mostly owing to their containing more or less of this 

 oxyde; and that, for this reason, they are usually the least 

 fertile; as the presence of iron, in any shape whatever, in 

 the soil, is unfriendly to vegetation. 



But redish-colored earths are often very prolific; parti- 

 cularly of the loamy kinds; the cause of \vhich may be, the 



11 



