162 GARDENING INDOORS AND UNDER GLASS 
to side of house at proper height, giving a thick 
coat of white lead at top to insure a tight joint with 
house. Now put one of the end bars in place, tak- 
ing care to get it exactly at right angles with ridge, 
and then lay down the sash-bars, enough more than 
16 in. apart to allow the glass to slip into place 
readily. Take a light of glass and try it between 
every fourth or fifth bar put into position, at both 
ridge and eave, as this is much easier than trying to 
remedy an error when half the glass is laid. Use 
“finishing ’’ nails for securing the sash-bars, as they 
are easily split. Next, with chalk line mark the 
middle of the roof sash-bars, and secure to them the 
one-inch pipe purlin, which will then be ready to 
fasten to the uprights already in place. Next, make 
concrete by mixing two parts Portland cement, two 
of sand and four of gravel or crushed stone with 
sufficient water to make a mixture that will pour like 
thick mud, and put the iron pipe posts in their 
permanent positions, seeing that the purlin is level 
and the posts upright. (If necessary, the purlin 
can be weighted down until the concrete sets.) 
Then put into place the ventilators, glazed, and the 
headers for the same — short pieces of wood, cut 
to go in between the sash-bars,— and fit these up 
snugly against the lower edge of the ventilator sash. 
When laying the glass in the roof, which will now 
be ready, use plenty of putty, worked sufficiently 
soft for the glass to be thoroughly bedded in it, and 
