126 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 



