HONEY-DEW, AND BLIGHTS. 331 



May, which is very destructive to fruit-trees in 

 orchards and open plantations, and against which 

 we know of no effectual remedy. This is what is 

 called a fire-blast, which in a few hours hath not 

 only destroyed the fruit and leaves, but often parts 

 of trees, and sometimes entire trees have been 

 killed by it. 



This is generally thought to be occasioned by 

 certain transparent flying vapours, which may 

 sometimes take such forms as to converge the sun's 

 rays in the manner of a burning-glass, so as to 

 scorch the plants they fall upon, and this in a greater 

 or less degree in proportion to their convergency. 

 As this generally happens in close plantations, where 

 the vapours from the earth, and the perspirations 

 from the trees, are pent-in for want of a free circu- 

 lation of air to disperse them, it points out to us 

 the only way yet known of guarding against this 

 enemy to fruits ; namely, to make choice of a 

 clear healthy situation for kitchen-gardens, or- 

 chards, &c. and to plant the trees at such a dis- 

 tance as to give free admission to the air, that it 

 may dispel those vapours before they are formed 

 into such volumes as to occasion these blasts. 



But blasts may also be occasioned by the reflec- 

 tion of the sun's rays from hollow clouds, which 

 sometimes act as burning mirrors, and occasion ex- 

 cessive heat. Against this there is no remedy. 



