THE FLORAL WORLD AND GARDEN GUIDE. 



73 



building lean-tohouses for early work,it is essential that the roof should 

 have a sharp pitch like that shown in figs. 1 and 2, because such a 

 powerful fire is not required to keep up the proper temperature 

 during a severe frost. The sun also shines more directly upon the 

 roof during the short days, and the vines derive the fullest possible 

 benefit from its rays. For the late summer and autumn crops a 

 flatter roof is desirable. 



In building span-roof houses, with roofs from twelve to sixteen 

 feet in length, the walls must be stronger than those required for 

 lean-to's, as the strain upon them is much greater. The ends should 

 also face due north and south, although a slight deviation from that 

 rule will not matter much. The roofs should have a sharper pitch 

 thau those of a bmaller size. Fig. 3 is a fair example of the angle 



P^» 



Fig. 3. — Span-roof Vinery foe. Summer and Autumn. 



at which they should be fixed. Front lights are not required for 

 any of the houses, although there is no objection to their employ- 

 ment where the cost of the structure is of secondary consideration. 

 It is, however, necessary in the case of houses ventilated at the top 

 to have ventilators at the front, and for this purpose, small wooden 

 shutters in the front wall will answer every purpose. The lights 

 ought not to rest upon the border, as shown in the accompanying 

 sketches, because it renders it extremely inconvenient to thin the 

 branches at the lower part of the vines, and also to attend to the 

 vines. The front walls, or walls and front lights combined, ought 



