No. 4.] GREENHOUSES. 389 



load and oil paint before they are nailed together. In fit- 

 ting the frame, all joints are nailed together with fine wire 

 nails. A fmme thus put together will last as long if well 

 painted as where the parts are mortised together, and the 

 cost is less. 



Glass. 



The glass most largely used in the construction of green- 

 houses is No. 2, or selected, double thick, for roof and 

 southern walls, while No. 3, double thick, may be used for 

 north walls, i)artitions, etc. The sizes used \a,ry very much, 

 but with the growing tendency to increase the size. That 

 most used is 1 6 x 24 to 20 x 30. 



Glazing. 

 All glass is put upon the sash bars bedded in soft putty, 

 that shall allow the glass to press down upon the sash bars, 

 filling up every possible space with the least possible 

 amount of putty. Putty containing one-fourth to one-third 

 white lead is perhaps the best. All glass must be solidly 

 fastened in with large zinc points, small brads or other nails 

 made for the special purpose. The glass may be lapped 

 from one-tenth to one-eighth of an inch, or it may be fitted 

 together with or without the zinc strip. If fitted without 

 the zinc strip, glass should be square, and the lowest edge 

 of each light be thicker than the upper, as in Fig. 13, that 

 the water ma}' run readily down the roof and not run into 

 the house. The use of the zinc strip (Fig. 14) makes a 

 very close, warm house ; but with one with a low pitch of 

 roof some water will work under, and the condensed mois- 

 ture on the inside will drip more than when the glass is 

 lapped or simply fitted together. The frame should be 

 thoroughly painted before the glass is set, again after the 

 glazing is done, and every second or third year, if it is de- 

 sired to preserve it the greatest length of time. 



Heating Greenhouses. 

 This is by far the greatest problem in greenhouse con- 

 struction, and there are many varying ideas in regard to it. 

 The one thino- that must be secured is an abundance of heat 



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