254 TREATISE ON THE CULTURE, &c. 



length, and this is afcribed to a blaft ! Luxuriant fhoots 

 fhould be flopped, and all fuperfluous wood fhould be cut 

 out : other wife they will exhauft a great part of the nourifh- 

 ment which fhould go to the fupport of the fruit- bearing 

 branches. 



There is another fort of blight that fo me times happens 

 pretty late in the Spring, viz. in April and May, which is 

 very deftructive to fruit-trees in orchards and open plantations, 

 and againft which we know of no effectual remedy. This is 

 what is called a fire-blaft, which in a few hours hath not only 

 deffroyed the fruit and leaves, but often parts of trees, and 

 fometimes entire trees have been killed by it. 



This is generally thought to be occafioned by certain tranf- 

 parent flying vapours, which may fometimes take fuch 

 forms as to converge the fun's" rays in the manner of a 

 burning-glafs, fo as to fcorch the plants they fall upon, and 

 this in a greater or lefs degree in proportion to their con- 

 vergency. As this generally happens in clofe plantations, 

 where the vapours from the earth, and the perfpirations from 

 the trees, are pent- in for want of a free circulation of air to 

 difperfe them, it points out to us the only way yet known of 

 guarding againft this enemy to fruits ; namely, to make choice 

 of a clear healthy fituation for kitchen-gardens, orchards, &c. 

 and to plant the trees at fuch a diftance as to give free ad- 

 miflion to the air, that it may difpel thole vapours before they 

 are formed into fuch volumes as to occafion thefe blafts. 



But blafts may alfo be occafioned by the reflection of the 

 fun's rays from hollow clouds, which fometimes act. as burning 

 mirrors, and occafion excefhve heat. Againft this there is no 

 remedy. 



