68 THE CULTURE OF THE GEAPE. 



that I have recommended during the night, when the 

 grapes are in flower ; but all the kinds cultivated here, 

 including the Tokay, Black Hamburgh, White Sweetwa- 

 ter, &c., uniformly set well with the heat above mention- 

 ed. Indeed, when the nights have been frosty, during 

 the time my vines were in flower, I have seen the ther- 

 mometer as low as 52° in the morning, and I never ob- 

 served that they sustained the least injury by this low 

 temperature. Too much dependence has hitherto been 

 placed on the influence of fire heat in the forcing of hot- 

 houses. The great art is to do with as little fire heat as 

 possible, and to take the utmost advantage of the heat 

 derivable from the sun's rays, consistent with giving a 

 sufficient quantity of air. The legitimate use of fire 

 heat is to prevent the bad effects of frosts, snows, and 

 inclement weather. 



" I may now say a few words on giving air. In clear 

 weather it should always be given early in the morning, 

 and taken away early in the afternoon. For example, 

 let a small portion of air be given between eight and 

 nine o'clock in the morning, and, if the day continue 

 clear, give more between ten and eleven, and take it all 

 away at three o'clock. I seldom let air into my vine- 

 houses after three o'clock in the afternoon. If air be ad- 

 mitted until the house is completely cooled, a large fire 

 may be necessary to support the requisite temperature ; 

 and it is evident that sun heat is better and cheaper than 

 fire hevit."—S&pt., 1838. 



By the foregoing, it would appear that the plan of 

 covering the border with heating substances, for the pur- 

 pose of raising the temperature of the border, was sug^ 



