NATURAL AND CIVIL 



a thermometer to the depth of ten inches below 

 the surface of the earth. Upon repeated trials 

 the quicksiher stood at fifty degrees : this ^vas 

 in a level open field, used for pasture or grazing-, 

 and fully exposed to the sun. The same ex- 

 periment was then made in the woods, where 

 the surface of the earth was covered with trees, 

 and never had been cultivated. To ascertain 

 Ihe gradual increase of heat at each place, the 

 observations were often repeated. The result 

 was as follows. 



The effect of cultivation with regard to the 

 lieat of the earth, so far as it can be collected 

 fiom these experiments, appears to be this : 

 Exposing the land to the full force of the solar 

 rays in this latitude, will produce an heat at the 

 depth of ten inches below the surface, ten or 

 eleven degrees greater than that which prevails 

 in the uncultivated parts of the country ; aiid 



