The Natural History of Se I borne 401 



that it falls in the night, because it is always first seen in 

 warm still mornings. 1 



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. 



1 Honey-dew is now known to be mainly produced by aphides, which 

 White here incidentally notices side by side with it, without suspecting 

 their casual connection. It is possible that a small amount of honey- 

 dew may be exuded by the plants themselves, but by far the greater por- 

 tion is undoubtedly due to the secretions of plant-lice. ED. 



2 C 



