ON VEGETABLES. 127 



We have already noticed the beneficial effects of the 

 motion which the wind communicates to trees. That of 

 the palm-trees in Egypt is so powerful, when agitated by 

 a high wind, that the French, when in that country, made 

 use of them as levers to draw up water from the Nile. 

 The motion of the stems raised the piston of the pumps, 

 which fell again by their own weight. 



Of the temperature of the atmosphere, which is the 

 point of greatest importance in vegetation, we have al- 

 ready fully treated. I have only to add, that plants which 

 grow in the plain, in countries of high latitudes, if trans- 

 ported to a warmer climate, must be cultivated in elevat- 

 ed situations. In Chili, for instance, potatoes grow at 

 an elevation of nine thousand feet higher than they will 

 grow in these climates. 



Emily. The degree of latitude is, then, the inverse of 

 the degree of elevation from the level of the sea ? 



Mrs. B. The one serves as a compensation for the 

 other. It is not, however, every species of plant which 

 can take advantage of this sort of compensation ; but the 

 greater number of plants will grow equally well at a high 

 latitude in the plain, or in a low one on a mountain. 



In an estimate made of the greatest height at which 

 several different species of trees will grow in the south 

 of France, it appears that 



The Larch grows at an elevation of 7200 feet. 

 The Birch .... 6000 feet. 

 The Beech . . . . 4000 feet. 

 The Cherry . 3000 feet. 



The Walnut .^ . . . 2400 feet. 

 Among the Cerealia, 



Rye ..... 6000 feet. 



Wheat ..... 5400 feet. 

 Turkey Corn . . . 3000 feet. 



The Vine 1800, or even so high as 2400 feet, 



if the situation be particularly favorable. 

 Emily. I recollect woods of birch-trees on the moun- 

 tains of Scotland, where they had to struggle against the 



709. Of the palm tree in Egypt? 710. Of potatoes in ChiliT 

 711. Of the correspondence between latitude and elevated situations for 

 the growth of plants'? 712. At what heights, will Larch, Birch, Beech, 

 Cherry, and Walnut grow? 713. And at what heights will Rye, 

 Wheat, Turkey corn, and the Vine, growt 



