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AGRICULTURAL CHEMISTRY.

manure, it is probably by entering into the compositionof the plant in the same manner as gypsum, phosphateof lime, and the alkalies. Sir John Pringle has statedthat salt, in small quantities, assists the decompositionof animal and vegetable matter. This circumstancemay render it useful in certain soils. Common salt,likewise, is offensive to insects. That in small quan-tities it is sometimes a useful manure, I believe, is fullyproved; and it is probable that its efficacy depends uponmany combined causes.

Some persons have argued against the employmentof salt, because, when used in large quantities, it eitherdoes no good, or renders the ground sterile ; but this isa very unfair mode of reasoning. That salt in largequantities rendered land barren, was known long beforeany records of agricultural science existed. We read inthe Scriptures, that Abimelech took the city of Shechem ,“ and beat down the city, and sowed it with salt,” thatthe soil might be for ever unfruitful. Virgil reprobatesa salt soil; and Pliny , though he recommends givingsalt to cattle, yet affirms, that when strewed over land,it renders it barren. But these are not argumentsagainst a proper application of it. Refuse salt in Corn­ wall , which, however, likewise contains some of the oiland exuviae of fish, has long been known as an admirablemanure. And the Cheshire farmers contend for thebenefit of the peculiar produce of their country.

It is not unlikely that the same causes influence theeffects of salt as those which act in modifying theoperation of gypsum. Most lands in this island, par-ticularly those near the sea, probably contain a sufficientquantity of salt for all the purposes of vegetation; andin such cases the supply of it to the soil will not onlybe useless, but may be injurious. In great storms the