310 NATURAL HISTORY 



in hot weather the effluvia of flowers in fields and meadows 

 and gardens are drawn up in the day by a brisk evaporation, 

 and then in the night fall down again with the dews, in 

 which they are entangled; that the air is strongly scented, 

 and therefore impregnated with the particles of flowers in 

 summer weather, our senses will inform us ; and that this 

 clammy sweet substance is of the vegetable kind we may 

 learn from bees, to whom it is very grateful : and we may 

 be assured 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 abovementioned : and, be- 

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

 the vast effluvia from our woodlands temper and moderate 

 our heats. 



LETTER LXY. 



TO THE HONOURABLE DAINES HARRINGTON. 



HE summer of the year 1783 was an amazing 

 and portentous one, and full of horrible 

 phenomena; for, besides the alarming me- 

 teors and tremendous thunder-storms that 

 affrighted and distressed the different coun- 

 ties of this kingdom, the peculiar hazo or smoky fog that 



1 The conjecture here hazarded concerning the origin of honeydew 

 is erroneous. Mr. Curtis has shown (Trans. Linn. Soc., vol. vi.) that 

 this substance is the excrement of the Aphides. In order to convince 

 a friend who was sceptical as to this fact, Mr. Rennie placed a sheet of 

 writing paper under a branch where some Aphides were feeding, and 



