54 Vegetable Stathh. 



In a long dry fcafon, therefore, efpecially 

 within the Tropicks, we muff have recourfe 

 for fufficient moifture (to keep Plants and 

 Trees alive) to the moift ftrata of earth, 

 which lie next below that in which the 

 roots are. Now moift bodies always com- 

 municate of their moifturc to more dry 

 adjoining bodies; but this flow motion of 

 the afcent of moifture is much accelerated 

 by the Sun's heat to considerable depths in 

 the earth, a$ is probable from the following 

 20th Experiment. 



Now 180 grains of Dew falling in one 

 night, on a circle of a foot diameter, == 

 113 fquare inches; thefe 180 grains being 

 equally fpread on this furface, its depth 



will be ttu part of an inch = 



M9 r U 3 x 254 



J found the depth of Dew in a winter night 

 to be the -^ part cf an inch ; fo that, if we 

 allow 1 59 nights for the extent of the fu tu- 

 rner's Dew, it will in that time arife to one 

 jnch depth. And reckoning the remaining 

 zo r o njghts for the extent of the winter'^ 

 Dew, it will produce 2.28 inches depth, 

 which makes the Dew of the whole year 

 amount to 3.28 inches depth. 



And the quantity which evaporated in a 



fair fummer's day from the fame furface, be- 

 ing 



