



38 



Vegetable Statkks. 



and trees, in proportion to the greater or 

 lefs convergency of the Sun's rays. 



The learned Boerhaave, in his Theory of 

 Chemiftry, p- 245- obferves, " That thofc 

 " white clouds which appear in fummcr- 

 " time, are as it were (o many mirrours, 

 « andoccafion excefTivc heat. Thefc cloudy 

 " mirrours are fometimes round, fome- 

 " times concave, polygonous, &c. when 

 tc the face of heaven is covered with fuch 

 " white clouds, the Sun mining among 

 "' them, iBUft of neceillty produce a vehe- 

 " ment heat; iince many of his rays, which 

 P would otherwife, perhaps, never touch 

 * l our earth, are hereby reflected to us ; thus 

 te if the Sun be on one fide, and the clouds 

 " on the oppofite one, they will be per- 

 " feci: burning glaifes. And hence the phze- 

 lt nomena of thunder. 



" I have fometimes (continues he) ob- 

 ferved a kind of hollow clouds, full of 

 hail and fnow , during the continuance 

 of which the heat was extreme; fmce by 

 fuch condenfation they were enabled to 

 reflect much more ftrongly. After this 

 came a (harp cold, and then the clouds 



difcharged their hail in great quantity ; 



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