VARIABLE WEATHER. 371 



vanced as to render influences manifest; but we 

 cannot perceive the injuries or benefits accruing 

 to a hidden circulation from particular events. 

 Every person who has been conversant with cattle, 

 must have remarked how uncertain their progress 

 in improvement has been ; that the abundant pro- 

 vision of one year did not prove equally nutritive 

 with the scanty product of some other : this fact 

 originates probably from the effects of atmospheric 

 impulse, either directly upon vegetation, or upon 

 the soil which produced the food collaterally, or 

 upon both collectively. In a wet season, water ap- 

 pears to nourish plants, or to supply their require- 

 ments principally : in a dry one, nutriment must be 

 obtained from the soil by means of the fibre of the 

 root, and hence particles are imbibed chemically 

 different ; a dry or a drained soil, producing short 

 and scanty herbage, will frequently improve the 

 condition of cattle more than an adjoining meadow 

 having a profusion of food, though probably no 

 chemical analysis could indicate the difference. 

 These periodical winds again, violent and distressing 

 as they often prove, are yet unquestionably essen- 

 tial in the economy of nature : our two seasons, in 

 which these commotions of the air most usually 

 become manifest, are about the equinoxes of au- 

 tumn and spring, periods which in many respects 

 have a similarity with each other. In the autumn 

 of our year, the foliage of trees and plants, &c. 



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