Lesson xrx.] FOGS, DEWS, &c. H3f 



surface, which is generally supposed to be warmer 

 than that above; but it is an incontestible fact, 

 that after sun-set, and during the night, in serene 

 weather, the air is coldest at the earth's surface, 

 and grows warmer the higher we ascend, till a 

 certain moderate height, commonly between 2O 

 and 100 yards : accordingly we find, that Dews and 

 Hoar Frost are more copious in valleys than in 

 elevated situations. When we recollect that winds 

 in great measure prevent the accumulation of Dew, 

 it can scarcely be doubted but that it depends upon 

 the abovexircumstance. 



It would be nearly inexcusable to conclude this 

 Lesson, without calling the attention of my young 

 readers, for a moment, to the beneficent and wise 

 laws established by the AUTHOR OF NATURE to 

 provide for the various exigencies of the sublunary 

 creation, and to make the several parts so depend- 

 ant upon each other, as to form one well-regulated 

 whole. In the torrid zone, and, it may be added, 

 in the temperate and frigid zones also, in summer, 

 the heat produced by the action of the solar rays 

 would be insupportable, were not a large portion 

 of it absorbed, in the process of Evaporation, into 

 the atmosphere, without increasing its tempe- 

 rature. This heat is again given out in winter, 

 when the vapour is condensed, and mitigates the 

 severity of the cold. The dry spring months are 

 favourable to agriculture, and the Evaporation, 

 which then begins to be considerable, absorbs a 

 portion of the heat imparted to the earth by the 

 sun, and thus renders the transition from cold to 



heat 



