18 THE FARMER AT HOME. 



in which one portion of the farm is in pasture and another arable \ 

 and these being successively changed. 



ALUM. A fossil salt, and mineral, of an acid taste, which 

 leaves in the mouth a sweetness, accompanied by an astringency so 

 considerable as to cause a sensation of shuddering. There are two 

 sorts of alum, the natural and the artificial, In a natural state, it is 

 said to be met with in Egypt, Sardinia, Spain, Bohemia, and other 

 places, and the counties of York and Lancaster, in England. On 

 account of its binding qualities, it is used in several mechanic arts, 

 and in medicine. In dyeing, it fixes and brightens colors; it 

 constitutes the tJasis of crayons ; it gives hardness and consistence 

 to tallow, in the manufacture of candles ; and wood, soaked in a so- 

 lution of alum, being incapable of taking fire, and answering the 

 purpose, also, of excluding the air is used for powder magazines. 



ALUMINE. One of the earths most important to the agricul- 

 turist, and entering largely into the composition of all rocks, clays, 

 and loams. It is the principle that gives peculiar tenacity and plas- 

 tic nature to clays ; rendering them heavy and impervious to water, 

 in proportion to the quantity contained in them. Alumine has a 

 great affinity for water, hence clay lands are usually more cold and 

 wet, and more difficult to cultivate than those into which it enters 

 in less proportions. Its presence in soils is, however, absolutely 

 necessary to prevent porosity ; and when combined in due proportion 

 with other principal earths it constitutes one of the surest ingredients 

 of a fertile soil. Much attention has of late been paid to the amelio- 

 ration of clay soils, arid of all the methods tried, thorough draining 

 has proved the easiest and most effective. When clay land is drained, 

 its texture is changed ; and the plants it naturally produces, as welJ 

 as those it is made capable of producing, are of a higher and more 

 valuable kind. Alumine is of much use in the arts ; it is extensively 

 employed as a cleaning powder ; as a mordant in dyeing ; and is the 

 basis of bricks, crucibles, and porcelain. 



AMMONIA. A transparent, colorless gas, of about half the 

 weight of common water, with an exceedingly pungent smell, extin- 

 guishes flame, and is fatal to life. It derives its name from the fact 

 that the ancients received it from that part of Lybia in which the 

 temple of Jupiter Ammon was situated ; or from Ammonia, one of 

 the Cyreniac territories* It is the same substance as " spirits of 

 hartshorn," employed for smelling bottles. To the agriculturist am- 

 monia is particularly interesting, because those substances that con- 

 tain the most of it are the most efficient manures, and act with the 

 most certainty and promptness. It is produced from soft or fluid 

 animal substances while in the process of decomposition, and this 

 change is rapid in proportion to the quantity of earthy salts they 

 contain. 



