CHEMICAL SCIENCE. 227 



Saussure, Daubeny and Draper, and they referred to some experiments 

 of their own, with the view of showing the probability that there is 

 more of the nitrogen derived from manure given off during the growth 

 of cereal grains than by leguminous and other crops ; and hence might 

 be explained the great demand upon nitrogenous manures observed in 

 the growth of grain. The authors suggested that here was an impor- 

 tant field of study, and that we have, in the facts alluded to, much that 

 should lead us to suppose that the success of a rotation of crops de- 

 pends on the degree in which the restoration of the balance of the 

 organic constituents of crops was attained by its means, rather than 

 on that of their mineral constituents, according to the theory of Liebig ; 

 whilst the means adopted to secure the former were always attended 

 with a sufficient supply of the latter. It was next shown, by reference 

 to what happens in actual practice as generally followed in Great 

 Britain, where corn and meat constitute almost the exclusive exports 

 of the farm, that the mineral constituents of the crops, taken collect- 

 ively, that is, as shown by the analysis of their ashes, could not be 

 considered as exhausted ; of these, however, phosphoric acid was lost 

 to the farm, in much larger proportion than the alkalies ; whilst the 

 latter would generally, by the combined agencies of disintegration of 

 the native soil and import in cattle food, be liable to diminution in 

 but a very insignificant degree, if not in some cases to accumulation. 

 Practical agriculture had, indeed, decided that phosphoric acid must 

 be returned to the land from sources external to the farm itself, viz., 

 by bones, guano, or other means. But, on the other hand, artificial 

 alkaline manures had generally been found to fail in effect. Indeed, 

 taking into careful consideration the tendency of all experience in 

 practical agriculture, as well as the collective results of a most labori- 

 ous experimental investigation of the subject, both in the field and in 

 the laboratory, it was the authors' deliberate opinion that the analysis 

 of the crops is no direct guide whatever as to the nature of the manure 

 required to be provided in the ordinary course of agriculture from 

 sources extraneous to the home manures of the farm that is to say, 

 by artificial manures. Reviewing, then, the actual facts of practical 

 agriculture, the authors could not agree with Baron Liebig, when he 

 asserted that our grand object should be to attain an artificial mixture 

 to substitute for farm-yard manure, which he admitted to be the 

 universal food of plants. The very practice of agriculture itself, as 

 followed in this country, necessitates the production of farm-yard ma- 

 nure, and all our calculations should be made on the supposition of 

 its use. 



FERTILITY OF NILE MUD. 



EHREXBERG, as the result of a careful microscopic examination of the 

 alluvial deposits of the Nile, has determined that the great fertility of 

 these depositions is not so much owing to any peculiar mineral consti- 

 tution, or to the presence of any great abundance of vegetable matter, 

 as it is to the vast accumulation of extremely minute forms of micro- 

 scopic animals, which, by their decomposition, enriched and fertilized 

 the soil. London Athen&um. 



