PROPAGATING HOUSE. 45 



that the greatest heat in the house will be under the frames ; 

 but there should be small doors placed along the entire 

 length, opening into the passage ways, which may be opened 

 to let the heat escape into the house when necessary to 

 raise its temperature, or to lower that under the frames. 

 The passage ways between the beds should not be less 

 than two and one half feet wide, and three feet is better. 

 The frames should not be over four feet wide, as it would 

 then be inconvenient to reach across them. A house eight- 

 een feet wide will allow of three rows of frames, and two 

 passage ways of three feet each ; or the outside frames 

 may be but three feet wide, and the center one, as it can 

 be reached from both sides, may be six feet. 



The places for ventilating the house may also be arranged 

 to suit the convenience or fancy, but they should be mainly 

 at the top. The sashes should be made in two sections 

 the upper one much shorter than the lower, and arranged so 

 that it can slide down over the other, and leave an opening 

 at the peak, as shown. Two of the sashes on the right-hand 

 side and one on the left are shown as open. If small roll- 

 ers are put in these upper sashes, they can be moved very 

 easily. Sometimes the sashes are made very short, not more 

 than three feet long, and then hung so that they will nearly 

 balance ; in this way they are easily managed by attaching 

 a small rope to one end. The short perpendicular sashes at 

 the sides of the house may be made so that they can be 

 opened ; but this will seldom be necessary, for if the upper 

 ones are opened the heat will pass off rapidly, and sufficient 

 fresh air will find its way into the house through the small 

 openings, of which there will always be more or less. 

 There are hundreds of methods of ventilating glass struc- 

 tures ; the object of all is the same, but these I have men- 

 tioned are the most simple and will answer every purpose. 



The slope of the roof should be at an angle of from 35 

 to 45 degrees ; the one shown in the engraving is at an 

 angle of 35 degrees, or very nearly. 



