GREENHOUSES FOR FORCING VEGETABLES. 75 



in the fall months, when the temperature outside is often 

 much higher than fifty at night ; but ia such cases, dur- 

 ing the months of October and November, the ventilating 

 sashes should be left up so as to keep the temperature at 

 night as low as practicable. Often the entire first crops 

 of Lettuce are lost for want of this precaution. Further 

 experience has also taught us the necessity of using glass 

 of a larger size. The size most used is twelve by sixteen, 

 put in the twelve inch way. The object of the larger 

 glass is to obtain the greatest amount of light. In glaz- 



Fig. 11. IMPROVED METHOD OF GLAZING. 



ing, the method now almost universally adopted is to bed 

 the glass in putty and tack it on the upper side with 

 large glazing points, using no putty on top, The glazing 

 points are triangular, one corner of which is turned down, 

 so that when it is driven in it fits against the lower edge 

 of each pane and prevents it from slipping down. A 

 great mistake is often made in giving the glass too much 

 lap. It should just be given enough to cover the edge 

 of the pane below from one-eighth to one-quarter of an 

 inch. If given much more the water gets between the 

 panes and when it freezes cracks the glass. 



It has been found that when the glass lies on the sash- 

 bars thus imbedded, the putty soon rots or wears out, 



