816 ALKALINE SALTS. 



about 2 per cent, of azote. The ash of a variety of coal of verjf 

 excellent quality gave of — 



Argillaceous matter (silica"?) not soltble in acids 69 



Alumina 5 



Lime 9 



Magnesia 8 



Oxide of manganese 3 



Oxide and sulpliuret of iron 16 



100 

 Coal ash also contains very minute quantities of alkaline salts, 

 which usually escape analysis when they are not especially inquired 

 after. One specimen analyzed in my laboratory, gave nearly 00.1 

 of alkali. Coal-ash is particularly useful on clayey soils ; it acts by 

 lessening the tenacity of the soil ; and further, doubtless, by the in- 

 troduction of certain useful principles, such as lime and alkaline salts. 



OF ALKALINE SALTS. 



It is impossible to doubt that salts having potash and soda for their 

 base are useful in agriculture. The influence of u^ood-ashes, and of 

 paring and burning is unquestionable ; and they are so, in some con- 

 siderable degree at least, in consequence of the salts of these bases 

 which they supply, and which always enter into the constitution of 

 vegetables. There are even certain crops which, in order to thrive, 

 require a particular alkali ; the vine, for example, the fruit of which 

 contains bitartrate of potash, and sorrel, which contains the binoxa- 

 late of the same base, must needs have supplies of potash. The 

 plants which are grown for the production of soda, the salsola, <5fC., 

 from which barilla is made, must come in a soil that naturally con- 

 tains a salt of soda, such as that of the sea-shore. 



It would appear, however, that the salts of soda or potash, must 

 not exceed a very small proportion in the soil. All the experiments 

 that have yet been undertaken with a view to ascertain the action 

 of different saline substances on growing vegetables, have led to no 

 very certain conclusion but this, that they must be used very sparing- 

 ly. M. Lecoq has published an account of some experiments, made 

 apparently with great care, which go to prove that common salt, in 

 the dose of from \\ to 2j cwts. per acre, favored the growth of barley, 

 wheat, lucern, and flax. Chloride of calcium and sulphate of soda, 

 he also found to have the same good effects. M. de Dombasle, how- 

 ever, came to conclusions totally opposed to them, with reference 

 especially to common salt, which, applied in the doses advised by M. 

 Lecoq, was not found to produce any sensible effeci. M. Puvis also 

 obtained results that were equally negative. It would perhaps have 

 been well had M. Lecoq begun by determining the proportion of 

 alkaline salts which existed previously in the soil on which he 

 conducted his experiments. If he operated on a soil that was either 

 destitute of these salts, or that contained them only in minimum 

 proportion, very probably he did good by adding them. 



Nitrate of potash has been repeatedly recommended ?r an agent 

 useful in agriculture. The conclusions that have been come to 

 however, from its use, are far from accordant. In the processta 



