[41] Peat pulverized and extracted with alcohol and ether to remove resinous substances.
[42] Data recalculated, omitting ash.
[43] Detmer, Landw. Versuchst., Vol. 14, 1871.
[44] A striking illustration of this is afforded by Naegeli’s experiment of enclosing several loaves of bread in a loosely closed tin-box. After eighteen months there remained only seventeen per cent of air-dry mouldy matter, totally destitute of starch.
[45] Abstract in Ann. de la Science Agronomique, Tome 2, 1887.
[46] Bull. No. 70 Minn. Exp’t Station, 1905.
[47] The humus determinations thus made, which include nearly all those made by German chemists, give the humus-content from 40 to 50% too high. The French determinations are mostly made by the method of Grandeau.
[48] The decrease of humus from wheat culture in the soils of Minnesota and North Dakota has been studied by H. Snyder and E. F. Ladd, respectively. In the prairie lands of the latter State the total organic matter in the first six inches of soil ranges from 15 to as much as 26%, and the humus alone from 4 to 7.8%.
[49] Precipitation with an excess of acid does not greatly change the results.
[50] In California soils this is mostly silica soluble in carbonate of soda.