The Natural History of Selborne 383 



On chalky and sandy soils, and in the hot villages about London, 

 the thermometer has been often observed to mount as high as 83 

 or 84 ; but with us, in this hilly and woody district, I have hardly 

 ever seen it exceed 80 ; nor does it often arrive at that pitch. The 

 reason, I conclude, is that our dense clayey soil, so much shaded by 

 trees, is not so easily heated through as those above-mentioned : 

 and, besides, our mountains cause currents of air and breezes ; and 

 the vast effluvia from our woodlands temper and moderate our 

 heats. 



