Action of the Atmosphere iipon neioly-deepened Soil. 417 



these three years the frost did not penetrate 1 foot into the ground. 

 The thermometer at that depth fell to 33^ F. on the 30th of Dec. 

 1815, and remained at the same point till the 12th of Feb. 1816, 

 but in the ensuing year it did not fall below 34'^. 



Here is a summary of the results in a tabular form : — 



Depth of 

 Thermometer. 



Maximum 

 Temperature 

 duriiiK 3 Years. 



Minimum 

 Temperature 

 during 3 Years. 



Range 

 during 3 Years. 



^5- 

 20- 

 15- 

 9-5 



Leslie also states that in the neighbourhood of Edinburgh, after 

 a long tract of rigorous weather, the frost was found to have pene- 

 trated 13 inches into the ground in a ploughed field, but only 8 

 inches in one piece of pasture ground, and 4 inches in another. 



Professor J. Forbes of Edinburgh found the annual range of 

 temperature at 3 French feet (= 3'2 English feet) below the sur- 

 face of the soil to vary in different strata as follows, being a mean 

 of three years : — 



o 



In trap tnfa 17"41 Falir. 



,, loose siind 19'S5 



„ compact sandstone .. 17"41 



(Brit. Assoc. JReport, 1S40, p. 73.) 



M. Quetelet, director of the observatory at Brussels, made from 

 1834 to 1831) some observations on the range of thermometers 

 buried in the ground at different depths. The ranges recorded by 

 liim as found at Brussels from 1834 to 1837 were : — 



Depth in English Feet and Inches. Annual Range in 



Feet. Inches. Degrees Fabr. 



Ih 23-90 



1 f) 22-39 



2 (j 20-43 



3 3 19-04 



6 5 13-66 



12 10 8-08 



25 7 2-03 



As to the earth, viewing the subject generally, diurnal varia- 

 tions of temperature are considered not to extend to a greater 

 depth than about 3 feet, and annual variations arc inferred to 

 ■cease at from G5 to 70 or bO feet. 



Some valuable results are exhibited in the Greenwich Obser- 

 vations for 1847 with reirard to tlie range of heat at different 

 distances below the eartli's surface. The following table shows 

 the mean monthly reading and mean daily range of two thermo- 



