288 THE NATURAL HISTORY [LETT. 



have a great effect on these marauders, and will keep them under. 

 Though wasps do not abound but in hot summers, yet they do 

 not prevail then, as I have instanced in the two years above- 

 mentioned. 



In the sultry season of 1783, honey-dews were so frequent 

 as to deface and destroy the beauties of my garden. My honey- 

 suckles, which were one week the most sweet and lovely objects 

 that the eye could behold, became, the next, the most loathsome ; 

 being enveloped in a viscous substance, and loaded with black 

 aphides, or smother-flies. The occasion of this clammy appear- 

 ance seems to be this, that, 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 sweet clammy substance is of the vegetable kind we 

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

 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 above-mentioned : and besides, our mountains cause 

 currents of air and breezes ; and the vast evaporation from our 

 woodlands tempers and moderates our heats. 



