gans. The general tendency of the alkalies is to give 

 solubility to vegetable matters j and in this way they 

 may render carbonaceous and other substances capa- 

 ble of being taken up by the tubes in the radicle 

 fibres of plants. The vegetable alkali likewise has a 

 strong attraction for water, and even in small quanti- 

 ties may tend to give a due degree of moisture to the 

 soil, or to other manures ; though this operation from 

 the small quantities used, or existing in the soil, can 

 be only of a secondary kind. 



The mineral alkali or soda, is found in the ashes 

 of sea- weed, and may be procured by certain chemical 

 agencies from common salt. Common salt consists of 

 the metal named sodium, combined with chlorine; 

 and pure soda consists of the same metal united to 

 oxygene. When water is present which can afford 

 oxygene to the sodium, soda may be obtained in se- 

 veral modes from salt. 



The same reasoning will apply to the operation 

 of the pure mineral alkali, or the carbonated alkali, as 

 to that of the vegetable alkali ; and when common salt 

 acts as a manure, it is probably by entering into the 

 composition of the plant in the same manner as gyp- 

 sum, phosphate of lime, and the alkalies. Sir John 

 Pringle has stated, that salt in small quantities assists 

 the decomposition of animal and vegetable matter. 

 This circumstance may render it useful in certain 

 soils. Common salt likewise is offensive to insects. - 

 That in small quantities it is sometimes a useful man- 

 ure, I believe it fully proved ; and it is probable that 

 its efficacy depends upon many combined causes. 



