140 Observations on Liehig's '^^ Organic Chemistry" 



be sufficient for a mixture of stable and dairy manure ; which is 

 the best way to keep it, as the water of the cow-dung corrects 

 the want of it in the horse-dung. Much, however, depends on 

 the warmth of the weather, and the quantity of straw, &c., in 

 the dung. When rotted so as to be easily cut with the spade 

 is perhaps the time when we will have most soluble matter at 

 least loss. 



It must be evident that experiments will settle such questions 

 with difficulty, when we consider that, in warm, moist, showery 

 weather, the dung may ferment in the soil as well as in the 

 heap ; it may even act as a drain with the undecomposed 

 straw, when the weather is very wet: in dry cold springs, on 

 the contrary, the moisture will soon be evaporated from the 

 small quantities spread in the soil, decomposition cease, and the 

 manure be hurtful ; whereas, had it been decomposed, it would 

 have retained its water and soluble food. In genei-al, I should 

 think rotting the manure to a certain extent most beneficial. 

 One of the greatest benefits of manure is, the water absorbed 

 by capillary attraction in its pores ; and it will absorb best when 

 rotted. Sir H. Davy was of opinion, that the powers of a fertile 

 soil may be tested by its powers of absorbing water. All organic 

 substances possess this in a great degree. Calcareous substances 

 absorb water, and keep the soil free, which is one of the greatest 

 benefits of lime ; sand, generally of quartz, keeps the soil open, 

 but retains no moisture ; alumina or clay absorbs water, but is 

 apt to agglutinise into solid impervious skin and lumps, prevent- 

 ing the access of heat and air to the soil, and keeping water 

 stagnant. A due proportion of quartz, or silex, and lime, is 

 therefore necessary in all soils to keep them open ; some white 

 sandstones, as that contained in heath mould, have so much 

 alumina and calcareous matter in their composition, that they 

 both keep open and retain moisture: it is of great use in peat 

 soil, which, if once thoroughly dried, is not easily moistened 

 again. The moisture absorbed by well decomposed manure is 

 of great value to the roots in dry weather ; it is a solvent for the 

 food, and is needed as a constituent of the food itself, affiarding 

 hydrogen and oxygen in the proportions found in most vegeta- 

 ble substances. Cow-dung containing most water is best for dry 

 sandy soils, and horse-dung for cold clayey soils ; but they de- 

 compose best together, and there is not so much difference in the 

 water contained when both are rotted: fresh straw manure drains 

 off the water. According to Dr. Madden's analysis, the water 

 in dairy manure is nearly three times that in stable manure; 

 the organic matter in both is nearly the same, almost 40 per cent ; 

 as however, in the dairy manure, only one half was soluble in 

 water and potash, while in the stable manure it was two thirds, 

 we see the benefit of mixing the two together, that both may 



