SOAPSUDS— SODA— SALT. 555 



prevent, however, the exhaustion of the potash, it is as well to spread 

 every year at the foot of the stools a certain quantity of the marc of 

 grapes ; this marc containing 2.5 per cent, of carbonate of potash, will 

 restore annually a large proportion of the potash which may have 

 disappeared from the trench." 



Soapsuds have an undoubted value because of their potash, irrespective 

 of the animal matter they contain. Upon Cabbages, Cauliflowers, and 

 all the Brassicaceous race they produce an immediate and very advan- 

 tageous effect. Potash constitutes the most valuable part of the ashes 

 left after a plant is burnt, and adds powerfully to the fertilising effect ( 

 of all composts to which they are added. 



Vegetable or wood ashes are esteemed the very best manure by the 

 Chinese. The weeds, which are separated from the land by the 

 harrow, with what they otherwise are able to collect, are carefuUy 

 burnt, and the ashes spread. The part of the field where this has been 

 done is easily perceived by the most careless observer. Indeed, the 

 vigour of the productions of those parts of their land where the ashes 

 have been applied, is evident as long as the crop continues on the 

 ground. The ashes of burnt vegetables are also mixed with a great 

 variety of other matters in forming the compositions which are spread 

 on the fields, or applied to individual plants. {Hort. Trans, v. 62.) 



Soda is regarded by Liebig and otbers as a natural 

 equivalent for potasb, although it is present in much smaller 

 quantities iu the structure of plants. Weigman and Polsdorff 

 foimd that the Salsola Kali which naturally grows in pre- 

 sence of a salt of soda (chloride of sodium) grew quite as well 

 without soda if a salt of potash (chloride of potassium) 

 were present ; but that it would not^ grow in soil containing 

 neither one nor the other. Hence, if this be so, we must 

 infer that provided soil contains alkaline matter it is im- 

 material whether that matter be soda or potash ; and also that 

 the salts of soda have as good an effect on vegetation as those 

 of potash. This point wants further examination. In the 

 meanwhile it may suffice to say that the influence of the salts 

 of soda is very analogous to that of salts of potash, as we 

 believe we see in nitrate of soda and nitrate of potash. But 

 in these instances it is not at aU settled whether their good 

 effect is owing to their nitrogen or their alkali. 



Common salt (chloride of sodium) is very frequently used as a 

 manure, and to plants naturally found on the sea-shore is indispensable. 

 The magnificent Asparagus of St. Sebastian owes its excellence in some 



