UPPER INDIA. 17 



144, says, "Composition, texture, and colour of soil are 

 important elements to be considered in estimating the effects 

 of the removal of the forest upon its thermoscopic action." 

 "Experience has proved," says Becquerel, "that when the 

 soil is bared it becomes more or less heated (by the rays of 

 the sun), according to the nature and colour of the particles 

 which compose it, and according ta its humidity, and that in 

 the refrigeration resulting from radiation we must take into 

 account the conducting power of those particles also. Other 

 things being equal, silicious and calcareous sands, compared 

 in equal volumes with different argillaceous earths, with cal- 

 careous powder or dust, with humus, with arable and with 

 garden earth, are the soils which least conduct heat. It is 

 for this reason that sandy ground, in summer, maintains a 

 high temperature even during the night. We may hence 

 conclude that when a sandy soil is stripped of wood the local 

 temperature will be raised. After the sands follow succes- 

 sively argillaceous, arable, and garden ground, then humus, 

 which occupies the lowest rank. If we represent the power 

 of calcareous sand to retain heat by 100, we have, according 

 to Schubler, 



For (silicious?) sand ... ... ... 95'6 



arable calcareous soil ... ... 74*3 



argillaceous earth ... ... ... 68*4 



garden earth ... ... ... 64'8 



humus 49'0 



" The retentive power of humus, then, is but half as great 

 as that of calcareous sand. We will add that the power of 

 retaining heat is proportional to the density. It has also a 

 relation to the magnitude of the particles. It is for this 

 reason that ground covered with silicious pebbles cools more 

 slowly than silicious sand, and that pebbly soils are best 



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