202 On Constructing a Peach -house. 



Mr. Wilkinson's last objections are, that my Vinery ad- 

 mits but very little light at the winter solstice; and that the 

 reflected rays are then " nearly the most possible, which 

 they actually would be if the angle were depressed only 

 6° more.*" I wish Mr. Wilkinson had stated the amount 

 of the beneficial influence of the solar light and heat, upon 

 Vines, when they have no leaves : and when the powers of 

 life, in them, are nearly in a state of perfect repose. I have 

 always observed, as many others have also done, that all 

 plants, which, like the Vine, are capable of bearing a very 

 low temperature without injury, never vegetate so strongly 

 in the spring, as when they have been, during winter, long 

 covered with snow : for under such circumstances, and 

 after so long and almost total suspension of vital action, 

 the powers of vegetable life appear to become extremely 

 excitable ; and therefore I should be happy to find Mr. 

 Wilkinson's calculation correct. But the solar rays fall 

 vertically on the roof of my Vinery, when the altitude of 

 the sun is fifty-six, as he states ; and the altitude of the 

 sun, in the latitude of this place, exceeds fifteen at the 

 winter solstice. The angle of incidence does not, there- 

 fore, appear to me to be so much as 41, nor the reflected 

 rays (according to Bouguer's table) quite 36' out of a thou- 

 sand, instead of being, as Mr. Wilkinson states, " nearly 

 the most possible and I am quite at a loss to compre- 

 hend how the angle of incidence can be 87° 30, when the 

 inclination of the roof of a Vinery is 6 degrees below 34, 

 that is 28, and the altitude of the sun more than 15. 



* See Horticultural Transactions, page lG3. 



