S26 
VEGETABLE GARDENING 
a very common size, but 16 x 24 is the standard size to- 
day, and is used to a much greater extent than any other 
size. It is generally laid with the sash bars 16 inches 
apart, while 24 inches between roof bars is not uncom- 
mon. Many greenhouse managers object to the bars 
being so far apart on account of the difficulty in making 
close fits between the laps. If the panes are graded 
before glazing so that lights of about equal curvature are 
placed together, there will be very little space between 
the laps. Twenty inches between sash bars is regarded 
as the proper distance by some growers, in which case 
20 x 24-inch glass is used. 
181. Glazing and painting. — A priming coat of paint 
should be applied to all wood parts before the work of 
construction is started. The glass is then laid in putty 
consisting of one part of white lead to five parts of putty. 
After filling the shoulders of the sash bars the glass is 
placed with the curve up, and pressed down firmly, 
squeezing out the surplus putty. This method of glaz- 
ing is much better than to use putty on the glass, because 
the putty remains in place and keeps out water and cold 
air and prevents the escape of heat from the house. 
When large glass is used, glazing points should be in- 
serted at the laps and midway between them. After the 
glass has been laid the house should receive two ad- 
ditional coats of paint and then be painted every year to 
insure maximum durability. 
182. Ventilators. — Provision must be made for ample 
ventilation. The most approved plan is to have a line 
of vents on both sides of the ridge. If devices are used 
to prevent the ventilating sash from binding, there is no 
reason why they should not be continuous. If such de- 
vices are not used, at least one line of glass should sepa- 
rate the ventilators. They may be hinged on the ridge 
or on the headers of the roof bars. Both systems have 
earnest advocates. The ventilation is more free when the 
