^{page 328 note 1} “Some Physical Properties of Soils in their Relation to Moisture and Crop Distribution,” Whitney, Weather Bureau, Bull. No. 4, 1892.

^{page 328 note 2} “Tobacco Soils of the United States,” Whitney, Division of Soils, Bull. No. 11, 1898.

^{page 330 note 1} “Preliminary Report on the Soils of Florida,” Whitney, Division of Soils, Bull. No. 13, 1898.

^{page 331 note 1} Bull. No. 16, 1899; see especially Lafayette, p. 115.

^{page 331 note 2} See Bull. No. 22, p. 55.

^{page 331 note 3} Weather Bureau, Bull. No. 4, p. 83. See also Gardner, “Electrical Method of Moisture Determination in Soils,” Bull. No. 12, Division of Soils, 1898.

^{page 331 note 4} Briggs, “Electrical Instruments for Determining the Moisture, Temperature, and soluble Salt Contents of Soils.” Bull. No. 15, Division of Soils, 1899.

^{page 331 note 5} Bull. No. 12, p. 15.

^{page 332 note 1} Bureau of Soils, Bull. No. 22. (In 1901 the Division of Soils was converted into the Bureau of Soils.)

^{page 333 note 1} Landw. Versuchs. Stat. 1866, VIII. 128.Google Scholar

^{page 333 note 2} Investigations in Soil Fertility, Bull. No. 23, 1904.

^{page 334 note 1} Briggs, “Filtration of Suspended Clay from Soil Solutions,” Bull. No. 19, 1902.

^{page 336 note 1} Physiology of Plants, Eng. ed. Vol. I. p. 171, 1900.Google Scholar

^{page 339 note 1} “Investigations in Soil Fertility,” Whitney and Cameron, Bull. No. 23, 1904.

^{page 340 note 1} “The Centrifugal Method of Mechanical Soil Analysis,” by L. J. Briggs, F. O. Martin, and J. R. Pearce.

^{page 341 note 1} “The Mechanics of Soil Moisture,” by L. J. Briggs, Bull. No. 10.

^{page 341 note 2} “Contributions to our knowledge of the Aëration of Soils,” E. Buckingham, 1904.

^{page 341 note 3} Buckingham calls it the “porosity,” but it is a pity to use an abstract noun for a concrete quantity with which the useful expression “pore space“ has for some time been associated.

^{page 342 note 1} “Soil Solutions, their nature and functions and the classification of Alkali Lands,” by F. K. Cameron, Bull. No. 17, 1901.

^{page 342 note 2} “Solution Studies of Salts occurring in Alkali Soils,” by Cameron, Briggs, and Seidell, Bull. No. 18, 1901.

^{page 343 note 1} “An Electrical Method of determining the soluble Salt Content of Soils,” Whitney and Means, Bull. No. 8, 1897; “Electrical Instruments for determining the moisture, temperature, and soluble Salt Content of Soils,” Briggs, Bull. No. 15, 1899.

^{page 344 note 1} “The Alkali Soils of the Yellowstone Valley,” Whitney and Means, Bull. No. 14, 1898.

^{page 344 note 2} Report of the Secretary of Agriculture for 1904, p. 70.

^{page 344 note 3} “Some Mutual Relations between Alkali Soils and Vegetation,” Kearney and Cameron, Report, No. 71, 1902.

^{page 345 note 1} “Growing Sumatra Tobacco under shade in the Connecticut Valley,” Whitney, Bull. No. 20, 1902.