36 GREENHOUSE CONSTRUCTION AND HEATING. 
the ridge by fixing a length of light quartering along 
each side of the ridge-plank, parallel with and 6in. 
or 8in. from it. These, cut into suitable lengths; may 
be supported by means of light ‘‘ principal” rafters, 
placed 3ft. or 4ft. or so apart—3in. by 2in. stuff will 
do for these, if the house does not exceed 10ft. or 
12f. in width. The longitudinal spaces thus left on 
each side the ridge may be covered in with Tin. or 
Qin. boards, with a cross-brace screwed on here and 
there to pre- 
vent warping, 
hinged to the 
ridge, and 
fitted with 
small case- 
ment stays. 
These are 
easily opened 
and closed, 
and admit the 
air more 
evenly all 
along the house, though they of course obstruct the light to 
a certain extent, but where placed directly over a narrow 
central pathway, this is not a matter of any great 
importance. 
In the successful culture of tomatoes, peaches, 
chrysanthemums, and greenhouse plants generally, air 
must also be admitted at the bottom of the house at certain 
times, and even vineries are the better for a moderate 
amount of ‘‘ side-air’’ in very warm weather ; while towards 
Fig, 21. 
