A Guide to the Scientific Examination of Soils; Comprising Select Methods of Mechanical and Chemical Analysis and Physical Investigation

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: another admixed part. If, for instance, this is done by sand, a soil when no longer plastic, but only binding, has to be classed among the loam soils. With a still greater content of sand, the soil also loses its binding power, and we have then a sandy loam or a loamy sand. Loams which may be considered as typical soils are a mixture of sand, clay, and humus, which are' spoken of as light when the sand predominates, and as heavy when the clay is in excess. These terms, light and heavy, do not refer to the actual weight of the soil, but to its tenacity and the degree of resistance it offers to the implements used in cultivation. Sandy soils are, in the farmer's sense of the word, the lightest of all soils, because they are the easiest to work, whilst in actual weight they are the heaviest soils known. Clay, though hard to work on account of its tenacity, is comparatively a light soil in weight. Peaty soils are light in both senses of the word, they being loose or porous and having little actual weight. Besides the soils proper which come immediately under cultivation, there are in most places a set of subsoils which differ from the true soils, and which cannot be ignored. The true soils, or, as they are sometimes called, the top soils, are usually of a darker color from the larger admixture of humus, whilst the subsoils are lighter in hue, yellow, red or bluish from the greater preponderance of the iron oxides. The soils are more or less friable in their texture, whilst the subsoils are tougher, more compact, and more largely commingled with rubbish and stone. The soils are usually a little more than mere surface coverings, whilst the subsoils may be many feet in thickness. THE OBJECT OF SOIL-ANALYSIS. Ix the analysis of soils we may be guided by geological or agricultu...