MANURES. 48 



been increased from 20 to 50 per cent. It may be applied 

 in minute portions! in the hill, or scattered broadcast, or 

 mixed with the muck heap. Its great affinity for water has 

 the effect, like that of gypsum, of attracting dews and atmos- 

 pheric vapor to the growing vegetation, by which it is supplied 

 with moisture in a period of drought much beyond what is 

 conveyed to such as are destitute of these manures. Salt is 

 also useful in destroying slugs, worms, and larvae which 

 frequently do much injury to the crops. 



SULPHATE OF SODA, (Glauber Salts,) SULPHATE OF MAG- 

 NESIA, (Epsom Salts,} AND SULPHATE OF POTASH. 



These are all useful manures, and they act on vegetation 

 in a manner similar to gypsum. This was to have been ex- 

 pected so far as the sulphuric acid is concerned, which is 

 common to each ; but their action is modified to a certain 

 degree by the influence af the base or alkaline ingredients 

 on the plants. The generally increased price which they 

 bear over gypsum, will prevent their use away from those 

 localities, where they exist in a state of nature, or where 

 they may be procured at low rates, near the laboratories in 

 which they are manufactured. 



NITRATE OF POTASH, (Saltpetre,) AND NITRATE OF 

 SODA. 



These are both found in a crude state in native beds, or 

 as an efflorescence ; and in this condition they can fre- 

 quently be bought at a price which will justify their use. 

 The first contains potash 461, and nitric acid 53 ; the 

 second, in its dry state, soda 36i, and nitric acid 63, in every 

 100 parts. Numerous experiments have been tried with 

 them on various crops ; but they have not thus far, afforded 

 very accurate or satisfactory results. In general, they give 

 a darker color and more rapid growth, and they increase 

 the weight of clover, grass and the straw of grain ; and the 

 former are more relished by cattle. But in the average 

 effects upon grain and roots, the statements are too much at 

 variance to deduce any well settled principles.* 



As a soak or steep for seeds, and especially when dis- 

 solved and added to the bed where they are planted, there 

 is no doubt of their great value in giving an early and vi- 



* From the decidedly beneficial effects, produced in numerous instances, may 

 we not reasonably infer, that they have generally been successful, where there has 

 been a deficiency of them in the soil? 



