HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This issue's cover: Apparatus designed by Lyman J. Briggs of the USDA Division of Soils around 1899 to measure soil moisture in the field. A modified Wheatstone bridge in the wooden box measured the electrical resistance between a pair of carbon electrodes buried in the soil. The measured resistance indicated water content. The third buried probe was used in compensating for the temperature dependence of the resistance measurement; it contained a small cell with a salt solution whose resistance varied in a known manner with temperature. The attention to fine detail in both the presentation of the instrument, and the portrayal of the background landscape, is exceptional in this signed work by Albertus Huthinson Baldwin (1845?-1944), a noted botanical illustrator. The image is from the USDA Yearbook of Agriculture for 1900. Please see p. 681-693, "The Life and Scientific Contributions of Lyman J. Briggs" by E.R. Landa and J.R. Nimmo.