66 MASSACHUSETTS HORTICULTURAL SOCIETY. 



and continuing up tlie roof between the lower laps of glass, and 

 by its expansion causing considerable breakage. Such breakages 

 are at all times expensive, but especially at such times as this, 

 when the temperature is low and the cold currents of air passing 

 through the broken glass may cause great damage to, or loss of 

 plants or bloom. Third, they provide at all times a free 

 passage for water from the roofs to drains or sewers, or, in many 

 cases when it is valuable for irrigating or other purposes, where a 

 supply of water under pressure cannot be obtained, to suitable 

 tanks or cisterns, built within the houses. They also prevent the 

 unsightly slopping over, which takes place with gutters whose first 

 contents have become frozen. 



We will now consider such details in the woodwork in connec- 

 tion with an iron frame house as may be different from those 

 already described in connection with the " All- wood," or " Sash- 

 bar " house. We find first the sill against which the side ventilators 

 close ; this is of a shape well known to all, and is cut from a two 

 by four-inch joist, the under side being milled with a plow groove 

 for the reception of the upper edge of the inner siding, and two 

 smaller grooves to prevent water creeping along under the sill inside 

 and running onto the boards. The upper side has the usual rabbet 

 for the sash to shut against, about one-half inch deep, and the sur- 

 face is beveled to shed water. The side ventilator is of various 

 depths for different purposes ; generally about twenty inches, the 

 top rail being rabbeted, as is also the small header which makes 

 connection between the sash and the gutter. This rabbeted joint 

 makes a very weather-tight and close connection. The eaves or 

 gutter strip is screwed to the upper surface of the eaves purlin, 

 and is fitted with a plow groove on the under side, for the reception 

 of the gutter's upper edges, which act as a weather-break. The 

 upper surfaces are beveled, the outer one to the pitch of the roof, 

 and the inner at such an angle as to give support for the foot of 

 the roof bars. 



At this point, I wish again to caution you against the very 

 common practice of having mortises cut in the strip for the 

 reception of the roof bars. This mortise and tenon style of 

 connection is very largely used, yet it is without question the 

 feature which leads to the first and most serious decay in a glazed 

 roof, no matter how perfectly we may make the tenon fit into the 

 mortise, or how careful we are to have all such joints painted 



