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 
v/hich 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/ 
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 HONOUEABLE DAINES BAREINGTON. 
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 
afirighted and distressed the different coun- 
ties of this kingdom, the peculiar haze or smoky fog that. 
^ The conjecture here hazarded concerning the origin of honejdew 
is erroneous. Mi\ 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, alid 
