THE CULTUBE OF THE GRAPE. 99 



pear to me, that want of warmth at the root of the vine 

 is the cause of the difficulty. 



These varieties of the foreign grapes which, in the 

 grapery, are now so much affected by this change in the 

 weather, when in the open air, and growing in the same 

 soil, do not suifer in the least, from this shanking. It 

 therefore appeal's evident, that the cause of the difiBculty 

 must be looked for in the temperature and ventilation of 

 the grapery. And these causes are, in my opinion, too 

 great and sudden changes in the temperature, and, per- 

 haps, too great heat at night relatively to the day. 



A low temperature at night is not injurious to the 

 vine,* on the contrary, it is probably beneficial. But the 

 vine under glass, when the sun is shining, is subject to 

 great heat, which rapidly accumulates, and, on the obscu- 

 ration of the sun's rays, as rapidly decreases. Here is 

 the cause of the trouble : vines in the open air do not 

 suffer from this pent up accumulation of heat, and are 

 not excessively excited thereby, and, when cool, cloudy 

 weather follows a warm, bright season, they are not 

 checked in the flow of the sap, as the vine is, under 



* In 1836, when visiting the vineyards near the Ehine, and on the bor- 

 der of the Lakes of Neufohatel and Geneva, I found the weather veiy cool, 

 as compared with the temperature of that season of the year in Maasa- 

 cliusetts, the thermometer, during: August and September, varying from 

 46", the lowest point at night, to 60°, and by day, the highest point being 

 76° in the shade. Notwithstanding the low point at which the mercury 

 fell during the night, the grapes ripened finely. The vines here, though 

 subject to an intense heat when the sun shone upon the vineyards upon 

 the side of the hills, were, nevertheless, in an atmosphere which did not 

 vary more *han 10° or 15° in the daytime, excepting when the sun was 

 shining upon them, and, being in the open air, there was no confined heat 

 there. 



