A CHAPTER ON fiRBEN-HOUSKS. 41 



ako. This drain shall be simply a long box, made of boards ; and 

 we will have it 1 foot by 2 feet, inside. From the mouth, 2, it shall 

 lead along, in a straight line, just below the level of the floor, to B, 

 where it descends so as to enter on a level with the floor of the hot- 

 air chamber. We will also have a smaller box, or drain, for fresh 

 air, leading from the bottom of the air-chamber to the open air 

 through the foundation wall, at 4, to supply the house with fresh 

 air. This air-pipe should be six inches in diameter, and there 

 should be a slide in it to enable us to shut it up, whenever the 

 weather is too cold to admit of its being open, without lowering the 

 temperature of the house too much. 



Now let us suppose all is ready, and that a fire is lighted in our 

 air-tight stove. The air in the air-chamber becoming heated, it 

 rises rapidly and passes into the green-house through the grated 

 opening at 1. Very quickly, then, in order to supply the deficiency 

 caused in the air-chamber, the air rushes through the cold-air drain. 

 This makes a current from the coolest part of the house, at 2, towards 

 the air-chamber ;. and, to make good again the lost air carried off 

 fi'om that end of the house, the warm stream which rises through 

 the opening at 1, immediately flows over the tops of the plants to- 

 wards the opposite end of the house, and, as it becomes cold again, 

 descends and enters the mouth of the cold-air drain, at 2. By taking 

 advantage of this simple and beautiful principle, that is to say the 

 rising of warm air, we are able in this way to heat every part 

 of the house alike, and have a constant bland zephyr passing over 

 the plants.* 



It is not easy to find any thing simpler or more easily managed 

 than this way of heating a small green-house. In this latitude, a 

 couple of cords of wood or a couple of tons of anthracite, will be 

 suflBcient for the whole winter ; for, it must be remembered, that no 

 matter how cold the day, the moment the sun shines there is not 

 the slightest need of a fire ; the temperature will then immediately 

 begin to rise. Usually after bright days, which are abundant in 

 our coldest winter- months, we shall not need to light a fire till one, 



* When a coal air-tight stove is used, there should be a water pan sus- 

 pended over it For a wood air-tight it is not necessary. 



