32 G SYLVA AMERICANA. 



perform the operations of analysis himself, so much the better, as 

 far as that, point is concerned ; but on the whole, such knowledge 

 and adroitness is not to be expected from men who have so 

 many other points demanding their attention, and who will, 

 therefore, effect their purpose much better by collecting proper 

 specimens of the soils to be studied, and sending them for analysis 

 to a respectable operative chemist. 



In selecting specimens, where the general nature of the soil of 

 a field is to be ascertained, portions of it should be taken from 

 different places, two or three inches below the surface, and 

 examined as to the similarity of their properties. It sometimes 

 happens, that upon plains, the whole of the upper stratum of the 

 land is of the same kind, and in this case, one analysis will be 

 sufficient : but in valleys, and near the beds of rivers, there are 

 very great differences, and it now and then occurs that one part 

 of a field is calcareous, and another part siliceous ; and in this 

 case, and in analogous cases, the portions different from each 

 other should be separately submitted to experiment. Soils, when 

 collected, if they cannot be immediately examined, should be 

 preserved in phials quite filled with them, and closed with ground- 

 glass stoppers. The quantity of soil most convenient for a perfect 

 analysis is from two to four hundred grains. It should be 

 collected in dry weather, and exposed to the atmosphere till it 

 becomes dry to the touch. 



The soil best suited for culture, according to the analysis of 

 Bergman, contains four parts of clay, three of sand, two of 

 calcareous earth, and one of magnesia : and, according to the 

 analysis of Fourcroy and Hassenfratz, 9216 parts of fertile soil 

 contained 305 parts of carbon, together with 279 parts of oil ; 

 of which, according to the calculations of Lavoisier, 220 parts 

 may be regarded as carbon : so that the whole of the carbon 

 contained in the soil in question may be estimated at about 525 

 parts exclusive of the roots of vegetables, or to about one sixteenth 

 of its weight. Young observed that equal weights of different 

 soils, when dried and reduced to powder, yielded by distillation 

 quantities of air somewhat corresponding to the ratios of their 

 values. The air was a mixture of fixed and inflammable gasses, 



