84- Recent Publications on Manures. 



water has little effect on it, when boiled on the fire for some 

 hours it will come off as thick as tar, and smelling like a dung- 

 hill ; yet, though repeatedly boiled at intervals for weeks on the 

 fire, and even scoured with diluted vitriol, it will come off for 

 many weeks smelling as at first. If the power of absorption is 

 so great, how long would the ordinary temperature of the soil 

 be in effecting the extraction of the ammonia ! I should not 

 at all approve of mixing blubber and oil with coarse ashes ; if it 

 be wished to absorb them, the soil is quite sufficient. The best 

 way to render these substances soluble, is to mix them with al- 

 kalies, and make them into a soluble soap, by mixing with 

 clippings of hedges and young branches (which possess most 

 potash) burned to ashes, and mixed with the oil. If lixiviated 

 and digested with one fourth part of quicklime, and the lie 

 poured off, the ashes will make the oil into a soluble soap and 

 render it available at once. The benefit of soap-suds and the 

 refuse from scoured yarn, are well known. " When am- 

 monia is decomposed in the plant," he says, " and the nitrogen 

 fixed as a constituent, all the hydrogen set free, unless what 

 goes to form the oils, resins, and other hydrogenated pro- 

 ducts in the plant, will be evaporated ; where the hydrogen and 

 oxygen exist in the proportions of water, as in sugar and 

 starch, they are exclusively formed from water." It is likely 

 these substances are mostly formed from water, but it will be 

 difficult to say exclusively ; though in the proportion of water, 

 the hydrogen and oxygen in these substances are not in the 

 state of water ; and if free hydrogen from ammonia is circulat- 

 ing in the elaborated sap or latex, it should be as eligible for 

 assimilation as that set free from the decomposition of water. 

 It will be the hydrogen in excess, from whatever substance it 

 came, that will be evaporated. When substances yielding the 

 same constituents are absorbed and decomposed in the plant, it 

 will be difficult to say what becomes of them, what are fixed, 

 and what evaporated or excreted. Besides the oxygen furnished 

 by water, oxygen gas is also absorbed in solution in water, and 

 from the air ; and what is not needed of these for the peculiar 

 acids of plants, may be assimilated as gum, starch, &c, while 

 the oxygen of the water may be set free and evaporated ; though 

 undoubtedly it will most often take place that the oxygen of the 

 water is made use of. 



As might have been expected, from his taking Professor 

 Liebig as a basis, Mr. Squarey adheres to the doctrine, that though 

 plants in a young state absorb carbonic acid from the soil, yet 

 afterwards they wholly depend on the air for their carbon: though 

 he allows that all water contains carbonic acid in solution, and 

 admits, as above, that the principal benefit of oils is in the carbon 

 they contain, he also rejects, as Liebig did, the idea of humus 

 forming any part of the food of plants. We shall see good 



