[ ^i8 ] , 



this; for being changed into water, part only of this water 

 is evaporated during the day, the reft remains to be converted 

 into ice by the 'cold of the enfuing night. This icy covering en- 

 creafes ths cold, till the vital principle *, and refiftancc given by 

 the formation of the bark to the entrance of cold, are overcome, 

 the fap frozen, and at the fame time the vefTels burft by the ex- 

 panfive force of freezing. This gives the reafon why plants in a fi- 

 tuation where the fun does not fhine on them to thaw the hoar-froft, 

 fuffer leaft in fevere feafons ; and that plants removed in Autumn, 

 unlefs the fhoots are completely hardened, will be more liable to 

 be injured by froft than thofe of the fame fpecies, the defcent or 

 fixation of whofe fap has received no check by tranfplanting. 

 Miller remarks, that thofe plants which were removed in 

 the Autumn of 1 739 were moftly killed by the cold of the 

 enfuing winter, while many of the fame fpecies efcaped uninjured : 

 and the fame may be always obferved after every fevere winter. 



Few deciduous fhrubs agree with fhade : their natural place is 

 the funny outskirts of the foreft ; and when otherwife fituated, 



long 



• See Smith's Tra£ls relating to Natural Hiftory, page 177, and Philofophical 

 Tranfaftions for 1788. 



f The foliowing experiments may throw fome light upon the caufe of plants remain- 

 ing unfrozen, when the furrounding water is frozen. Water entlofed in fealed glafs 

 globules remains unfrozen, 'till the thermometer defcends to twenty-four ; unfealed 

 ones freeze and burft immediately on being cooled down to freezing water. Oil 

 enclofed in the fame kind of globules continued unexpanded, and confcquently the 

 globules unbroken, when placed in a mixture of fnow and fal ammoniac, and cooled 

 below o. 



