CH. Yll.] THE FRUIT AND SEED. 237 



In latitude 52°, Mr. Knight found, from lengthened 

 experiment, that the best angle is about 34°, con- 

 sidering the services of a hot-house through the year ; 

 and to illustrate this, he gave the preceding diagram. 



About the middle of May, the elevation of the sun 

 at noon, corresponds nearly with the asterisk a ; in 

 the beginning of June, and early in July it will be 

 vertical at *&, and at midsummer at c, only six 

 degrees from being vertical. The asterisk d points 

 out its position at the equinoxes, and e its position 

 at midwinter ^ 



If the best glass be employed it is an excellent 

 plan to have it put double in each sash, an interval 

 of half an inch being left between the two panes, and 

 a small hole at the comer of the inner one to pre- 

 vent the glass being broken by the expansion or con- 

 traction of the air between. This confined air is one 

 of the worst possible conductors of heat, keeping the 

 house from being rapidly cooled during the coldest 

 weather ; and thus is effected a very great economy 

 of fuel, whilst little or no extra interruption is 

 caused to the entrance of light. 



Moisture. — Every fruit-bearing tree requires a 

 larger supply of moisture during the growth of its 

 fruit, and in proportion to its abundance, than at 

 any other season, and for the obvious reason that, as 

 the fruit is a reservoir of accumulated and elaborated 



'' Hort. Society's Trans. 



