Observations on Liehigs " Organic Chemistry.'^ 137 



be in some measure supplied by the soil itself, phosphoric acid 

 being a constituent of all, even the poorest, soils. To talk of 

 manuring with a solution of glass is startling; if potash is added 

 to the soil, the silicic acid generally abounds, and silicate of 

 potash (glass) is formed in the soil. It requires considerable 

 heat ; but the roots likely assist, as in all our grain crops there 

 seems no want of it. Glass is most commonly made in this 

 country from soda. Soda is the most powerful solvent, and will 

 be of most use if the food is absorbed in solution and the bases 

 returned, which, I think, is likely to turn out to be the case. 

 Chloride of sodium (common salt) is very poisonous, if in excess. 

 It will be seen, in attentively perusing the analysis of manures 

 extracted from Dr. Liebig's work, that they have been made on the 

 presumption that the atmosphere is the source of carbon to plants 

 by the leaves, and that ammonia and salts are the principal requi- 

 sites to be furnished by manures. It will alter the case materially if 

 we take a different view of the subject, and suppose the principal 

 part of the food to be got by the roots. If we cut down a tree 

 on the stem to near the roots, it will spring away with the 

 greatest vigour; will it do the same if the roots are cut off near 

 the stem, though we keep the atmosphere saturated with mois- 

 ture, carbonic acid, and ammonia? If the leaves are the only 

 source of carbon, whence the great growth when there are no 

 leaves to feed it, or how does the cutting of the roots prevent 

 the action of the leaves ? Can we rest assured that soluble sub- 

 stances will not be assimilated in the plant, when taken up by the 

 roots? when we see that the same substances, as sugar, starch, 

 &c., formed in the plant, in seeds, tubers, and bulbs, around 

 buds, and in all parts of the plant, are taken up in spring, dis- 

 solved in the ascending sap, and, assisted by the action of nitrogen 

 (so powerfully described by the professor, and which the soluble 

 substances absorbed by the fibres will obtain so readily from the 

 nitrogen abounding in the roots), assimilated by the plant. If 

 the one are assimilated, so undoubtedly will be the other. If we 

 can add to this the action of alkalies in rendering food soluble, 

 and being separated in the plant, and again returned to dissolve 

 more food; if we take all these into account, we will find many 

 useful constituents in manures besides the earthy salts and am- 

 monia. In green and soft vegetables we will find matter nearly 

 in a state of solubility, which must be put into the soil as soon 

 as possible, or mixed up with other substances more solid, or 

 with earth, to preserve as much as possible of the volatile sub- 

 stances. If the vegetable substances are more fibrous and 

 woody, as clippings of hedges, sawdust, tanner's bark, peat, &c., 

 some substances in a state of fermentation, or which have a 

 tendency to induce that state, should be added. Quicklime is 

 of use in inducing a commencement of decay, by extracting 



