[31] The word crumbs, which is generally understood as meaning a relatively large, loose aggregate, seems preferable to the word kernels, suggested for the same by King (Physics of the Soil, p. 110). Kernels are understood to be bodies rather more solid than the surrounding mass, and do not convey the idea of loose aggregates. The word “Krümelstructur” (crumb-structure), adopted by Wollny for this phenomenon, has both fitness and priority in its favor.
[32] Wollny (Forsch. Vol. 20, p. 13 ff., 1897) records similarly high shrinkages in his experiments.
[33] A totally different kind of “hog-wallows,” occurring in California and the arid region generally, have been described in a previous chapter under the head of Aeolian soils ([See chapt. 1, p. 9]).
[34] In driving a light carriage over the land represented by No. 643 above, after a light rain, the wheels gathered up so much soil within a hundred yards as to render it necessary to stop and chop it off the tires by means of a hatchet. This is a common experience in the black prairie lands of Texas.
[35] Schübler (Grundsätzed. Agrikulturchemie, 1838) ascribes the crumbling of calcareous clay soils to the difference in the contraction of calcareous sand and the clay substance. But it is doubtless more directly connected with the flocculation of the latter by lime.
[36] The antiseptic properties of sour humus are well exemplified in the perfect state of preservation in which the remains of animals, wood implements, etc., are found in bogs into which they have sunk in prehistoric times.
[37] See Müller, Natürliche Humusformen.
[38] Reports of the Rhode Island Exp’t Station, 1895, and ff.
[39] Wollny, Zersetzung der Organischen Stoffe, pp. 242, 243.
[40] Peat pulverized and extracted with alcohol and ether to remove resinous substances.