214 



On the Physical Properties of Soil. 



it will appear, that we may conclude, from this power of a soil, 

 when it exceeds a certain fixed minimum or maximum, with great 

 probability on the unfruitfulness of a soil ; but that, with the soils 

 which most frequently occur, and have a medium power of from 

 40 to 60 per cent., many cases present themselves in which, 

 without the assistance of chemistry, we should remain in doubt 

 as to the fruitful ness or unfruitfulness of a soil : since the fine- 

 ness of the particles of earths has so considerable an influence 

 on their power of containing water, we ought on that account only 

 to be very doubtful in forming conclusions respecting their con- 

 stituent parts. A power of containing water, of from 25 to 28 per 

 cent., which, according to this Table, indicates a pure sterile lime- 

 stone soil, might equally belong to a soil consisting of siliceous 

 sand or gypsum powder ; a power of containing water of from 60 

 to 62 per cent., belonging, as it most frequently does, to a fertile 

 heavy soil, as given by the Table, may moreover apply equally 

 to a clay soil (between a sandy clay and a loamy clay) without 

 humus, and perfectly sterile ; likewise a power of containing 

 water of from 87 to 90 per cent., which this Table sets down 

 as a marl soil or calcareous sterile clay, may belong to very 

 fertile arable and garden soils, supplied with the due quantity of 

 humus. 



The minuter distinctions of the power of containing water, in 

 the case of mixed earths, may be ascertained from the following 

 comparison, in which I distinguish the fertile and the sterile 

 earths, arranged according to their power of containing water by 

 weight; subjoining to each kind, for the purpose of further com- 

 parison, a brief notice of its predominating materials, as far as 

 they have an especial influence on that power, with remarks 

 appended on its fertility, (the subject of the chemical elements 

 of compound soils being treated more minutely in another section 

 of my work.) The soils of the Rhein-Gau here given were 

 examined, in reference to this object, by Professor Geiger, of 

 Heidelberg those of the country of Gottingen, East Friesland, 

 and Liineburg, by Dr. Sprengel of Gottingen; j and the remainder 

 by myself. 



* Metzger's Rhenish Vine-Cultivation. Heidelberg, 1827, p. 225. 

 t Erdmann's Journal of Technical and Economical Chemistry, No. 4, 

 1 829, p. 1, &c. 



