35 



that the water will run away from the frout wall. When iron 

 frames are used the front wall may be out of perpendicular from 

 four to six inches to aid in this discharge of the drip. Another 

 means of carrying the drip away from the front wall is obtained 

 by inserting into the plate of ordinary form a " drip board "six to 

 eight inches wide, as in 'Fig. 8. 



Ventilators. — These should be placed about the houses in such 

 a way as to give the proper amount of air for the crop grown, and 

 be used for this purpose alone, and not to regulate the temperature. 

 The skilful fireman will so regulate his fires as to require but little 

 movement of the ventilator to keep up the even degree of heat 

 required. 



For forcing roses and other plants requiring a high temperature, 

 and that are easily injured by a draught of cold air, the ventilators 

 should be placed only on the south side, and be hinged so as to 

 open at the top, that the cold air may enter at the highest point 

 and become warmed before it comes in contact with the tender 

 plants. For growing plants that succeed at a low temperature, 

 and that require much air, ventilators are often placed on both 

 sides of the roof, at the front and sometimes on the back walls. 

 One advantage of having ventilators on all sides of the house is 

 that by opening all a very short distance a large amount of fresh 

 air may be admitted without causing a chill ; but, on the other 

 hand, the more ventilators used in the construction of the house 

 the greater the cost. Side ventilators are difficult to construct 

 and operate, as they must shut into a frame in order to make a 

 close joint, and continued moisture during the summer and freezing 

 weather in the winter cause them to open with difficulty, and 

 they are soon wrenched and twisted out of shape. Ventilators on 

 the roof are now constructed with a groove on the under side, 

 which shuts down upon the tongue of the sash bar, as in Fig. 10, 

 thus making a close joint and .yet opening easily in all weathers. 

 All sash fittings, like hinges, etc., should be put on with brass 

 screws, as iron screws rust very quickly and soon rot out the 

 wood through which they are driven. 



Pain t hi g. 

 In building greenhouses all the framework should be painted 

 with a priming coat of tliin lead and oil paint before being fitted, 

 and then all joints covered with thick white lead and oil paint 

 before they are nailed together. In fitting the frame all joints are 

 nailed together witli fine wire nails. A frame thus put together 

 will last as long if well painted as where the parts are mortised 

 together, and the cost is much greater in the latter case. 



