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The Soil Physics Contributions of Edgar Buckingham

^a U. S. Geological Survey, MS-421, 345 Middlefield Road, Menlo Park, CA 94025
^b U.S. Geological Survey, MS-430,12201 Sunrise Valley Drive, Reston, VA 20192

View larger version (131K): [in a new window]   Fig. 1. Portraits of Edgar Buckingham (a) at age 20; (b) with daughter Katharine, circa 1905, during the time of his soil-physics work at the BOS; (c) in 1923; and (d) on unknown date. The scar visible on his cheek in (b) was the result of an abscess and surgeries performed to treat it during 1893–1895 (Buckingham 1900b). The photograph (c) was published by Gardner (1986) and (d) was published in the National Cyclopaedia of American Biography (1941a). Photographs (a), (b), and (c) courtesy of Thomas K. Hunt.

View larger version (43K): [in a new window]   Fig. 2. Timeline of events related to soil physics research at the USDA BOS 1901–1907.

View larger version (31K): [in a new window]   Fig. 3. Water lost over time by Takoma loam soil: soil under humid conditions (experiment conducted at room temperature) (A), soil under arid conditions (experiment conducted with heating of the top 4 cm of the soil column and the air at the soil surface) (B), water under arid conditions (C), water under humid conditions (D) (Buckingham, 1907, p. 21).

View larger version (37K): [in a new window]   Fig. 4. Measured retention curves for six soils (Buckingham, 1907, p. 32). The symbol A is a proportionality constant depending only on the units chosen for .

View larger version (14K): [in a new window]   Fig. 5. Buckingham's illustration of capillary water held in a prismatic wedge (Buckingham, 1907, p. 45).

View larger version (29K): [in a new window]   Fig. 6. Hydraulic conductivity relation as a function of water content, (above) by Buckingham's semiempirical formula (Buckingham, 1907, p. 46) and (below) as a sketch with characteristic segments of the curve labeled A-F (Buckingham, 1907, p. 43).

View larger version (19K): [in a new window]   Fig. 7. Data from Buckingham's experiments measuring water flow driven by a difference in matric potential. The ordinate is the mean change in water content of a dry and a wet sample of soil brought into contact in a column, divided by the initial difference in the two water contents. This quantity correlates with the flow rate induced by a difference of water contents, in effect representing the soil-water diffusivity. The results here for a Podunk sandy loam suggest that the diffusivity has a minimum at about 16% water content by weight. The symbol A labels these results as being from experiments of 4-d duration. The different point symbols correspond to minor experimental variations. (Buckingham, 1907, p. 59.)

View larger version (45K): [in a new window]   Fig. 8. Front and back of 5 Sept. 1906 postcard from Buckingham to Cameron. It appears to be annotated later, possibly by Cameron, with "9/7/06," likely the date of receipt, and doodle-like pennings of two styles of the Greek letter .

View larger version (35K): [in a new window]   Fig. 9. The 11 Sept. 1906 letter from Buckingham to Cameron. At upper left is Buckingham's sketch of the thought experiment proposed by Cameron, which Cameron proposed would generate perpetual motion according to Buckingham's new theory of unsaturated flow.

View larger version (38K): [in a new window]   Fig. 10. First page of Buckingham's intended conclusion to Bulletin 38, written in November 1906.