420 EXPERIMENT STATION EECOED. 



the Mitsclierlicli metliod often furnishes a simpler, more practical, and more 

 exact basis for classifying soils. 



Bibliography of North American geology for 1909, with subject index, 

 J. M. NicKLES (U. S. Geol. Survey Bid. J/Jf-'f, pp. i7//). — This bibliography is 

 arranged on the same plan as those for previous years. It contains references 

 to a number of important articles on soils, phosphates, and other minerals of 

 agricultural importance. 



Mineral resources of Virginia, T. L, Watson {Lynchburg, Va., 1901, pp. 

 XXXI^iMS, plf<. 83. pgft. 101). — This handbook, prepared in connection AA^th 

 the Jamestown Exposition, is based mainly upon the work of Rogers and Hotch- 

 kiss, the United States Geological Survey, and the Geological Survey of Vir- 

 ginia, " conducted jointly for two years by the board of visitors of the Virginia 

 Polytechnic Institute and the state board of agriculture." It contains sections 

 on the following minerals of special agricultural importance: Limestone, feld- 

 spars, phosphates, nitrates, gypsum, and marl. 



General classification of Florida soils {Fla. Quart. Bui. Agr. Dept., 20 

 {1910), No. 2, pp. 27-38). — Soils of the following general classes are described: 

 Second and third rate pine lands, high hammock, low hammock, and swamp 

 soils. 



Notes on the soil occurring in the area served by the Barren Jack irriga- 

 tion scheme, F. B. Guthrie {Agr. Gaz. V. S. Wales, 21 {1910). No. 8, pp. 663- 

 666). — A general description and results of physical and chemical analyses of 

 four classes of soils of this region are given, and the agricultural possibilities 

 of each class are discussed. The chemical analyses show relatively low con- 

 tents of humus and nitrogen. 



Report on the sand dunes of New Zealand, L. Cockayne {WeUington, N. Z.: 

 Dept. of Loitids, 1909, pp. 30, pis. 9). — This report deals in detail with the area, 

 geology, and botany of these dunes, which occupy over 300,000 acres of land. 



The Demerara soil problem (Internat. Sugar Jour., 12 {1910), Nos. 136, pp. 

 168-171; 137, pp. 228-231; ahs. in Chcm. Abs., J, {1910), No. 16, p. 2177).— It is 

 pointed out that the system of continuous cane growing, the absence of any 

 attempt to maintain the humus supply of the soil, and the concentration of sub- 

 soil drainage water are rapidly unfitting the land for future use. To place the 

 cultivation in a satisfactory position it will be necessary to change the system 

 of planting, to adopt- mechanical tillage, and to introduce a system of green 

 manuring and crop rotation. 



Studies of the changes occurring in heated soils, S. U. Pickering {Jour. 

 Agr. Sci., 3 {1910), No. 3, pp. 258-276, figs. 5; ahs. in Jour. Soc. Chem^ In&us., 

 2.9 {1910), No. 20, p. 1217).— Iw previous investigations (E. S. R., 20, p. 1015) 

 it had been shown that soils heated to from 60 to 150° C. developed a soluble 

 organic substance which was toxic to the germination of seeds. In the investi- 

 gations here reported a further study was made of the character of this sub- 

 stance and of the changes which it undergoes when kept under various condi- 

 tions. This study was preceded by an inquiry as to the trustworthiness of the 

 determination of soil extracts. 



" The water extracts obtainable from soils are of constant composition as re- 

 gards organic matter when the time allowed for the exti'action varies from 20 

 to 320 minutes, the temperature from 7° to 23°, and the proportions from 5 to 

 10 of soil to 100 of water. The inorganic matter is not affected by the time, 

 but is by the temperature and proportions. 



" The increase in soluble matter produced by heating a soil, and the accom- 

 panying toxic qualities toward the germination of seeds in it, is gradually re- 

 duced by exposing these soils in a moist condition to the air, even under aseptic 



