which may or may not lend themselves to modification 

 in the field. From the fact that type is of primary im- 

 portance in choosing a soil, texture in its relation to con- 

 ductivity might be considered first. From the work of 

 Wagner ^ and Potts ^ it is clearly established that the 

 coarser the texture of a soil, the faster the rate of conduc- 

 tion of heat will be, other factors remaining constant. 

 Data quoted from the findings of Bom oucos ^ substantiate 

 these results : — 



Conductivity or Vaeious Soils as Measured by the Time 

 Required for a Thermometer 7 Inches from the Source 

 OF Heat to Show a Rise in Temperature 



q ., Relative Rate of 



Conductivity 



Sand LOO 



Loam 1.81 



Clay 1.77 



Peat 4.61 



Such results as these are only comparative and qualita- 

 tive. The difiiculties of quantitative determinations are 

 so beset by error that only one investigator has as yet 

 made any consistent attempt along this line. Patten,^ 

 Mrho has prosecuted such an investigation, finds that such 

 work may be vitiated by thermometer spacing, size of 

 thermometer, error in readings, moisture control, and 



1 Wagner, F. Untersuehungen uber das Relative Warme- 

 leitungsvermogen Verscluedner Bodenarten. Forseli a. d, 

 Geb d Agri -Physik, Band VI, Seite 1-51. 18S5, 



^ Potts, E. XJntersucliungen BetreJBfend die Fortpflan- 

 zung der Warme in Boden dureh Leitnng Landw. Ver. Stat , 

 Band XX, Seite 273-355. 1877. 



^Bouyoncos, Q. J An Investigation of Soil Temperature, 

 Michigan Agr. Exp. Sta , Tech Bui 17, p 20 1913. 



^ Patten, H E. Heat Transfer in Soils. U. S. D. A., Bur, 

 Soils, Bui. 59. 1909. 



