STRUCTURE OF A GLASS HOUSE. 99 



ventilator, d, is made of matched pine board cut into eighteen- 

 iuch lengths, and battened by four-inch strips on the upper 

 and under sides, as seen in the figure, so as to break the joints 

 and prevent the escape of heat. The ventilator runs the 

 length of the section, and is raised by pushers connected to 

 an iron rod. The brace, I, is placed at intervals of two and 

 a half feet. 



All this work is put together with nails, the sides of the 

 gutters requiring a forty d size. To give firmness and pre- 

 vent the warping of the sash-bars, which, as I have said, are 

 of spruce, an inch strip of hard pine, running the length of 

 the section and binding them together on the under side, 

 about four and a half feet from either end of the bar, will be 

 found quite sufficient. A practical test of this form for sev- 

 eral years proves it to be permanent and very economical. 

 Spruce is used because it is stronger and cheaper than pine. 

 As every part can be got out at the mill, and can be put 

 together by any ordinary workman, the cost of construction 

 is reduced to a minimum. 



A glance at the diagram will indicate some of the advan- 

 tages of this form for the purposes for which it is designed. 

 First. The position is sheltered to the utmost possible extent. 

 This fact not only secures a saving of more than half the 

 ordinary cost of fuel, but it also insures great steadiness in 

 the temperature and comparative safety against the accident 

 of frost. Second. A large, compact, square space, with but 

 four outside walls, is a saving in construction and in exposure 

 to the cold, and also by its size is a safeguard against sudden 

 changes. After a bright day, the earth — the whole hillside — 

 gets so thoroughly warm that there would be little frost even 

 in the coldest nights, and without fire. Third. The flood of 

 sunlight is, indeed, the main advantage. The paramount 

 importance of this condition will be acknowledged by all who 

 have had experience in the winter-culture of plants. By a 

 glance at the diagram, it will be seen that in border plant- 

 ing, as at ff, the ground and plants will have the direct rays 

 of the sun. In the use of tables, as at e e, not only the ordi- 

 nary space for sunlight is secured, but it is evident that the 

 space under the tables will have a good degree of light, — 

 sufficient for ferns, mushrooms, rhubarb, etc. As the ven- 



