46 THE GRAPE. 



tween plants and animals is in this respect the same, and 

 every body who is possessed of ordinary observation must 

 be able to discern how different is the air that is raised in 

 temperature by a red-hot stove, even though a vessel of 

 water be kept upon it, to what it is when raised to the 

 same temperature by the sun's power. We also know, 

 that if we were able to control other circumstances accord- 

 ing to our wants for the time being, success would more 

 often attend our operations, providing we could exactly 

 imitate the warmth of nature. If this be true, it must 

 then be certainly to our own interest to approach as near 

 as we can to this desideratum. To come to our point, a 

 capacious flue gives a greater surface exposed to the ac- 

 tion of the heat, without becoming hot enough to bring 

 about so much chemical action as to burn the air inside of 

 the house, while a small one is sure to do so, at any rate, 

 in that part next to the furnace. To be effectual in this 

 respect, a flue ought not to be less than eighteen inches 

 high, by twelve inches wide in the clear ; and if raised up 

 by placing supports underneath at intervals on the length, 

 with fire-proof tiles to form the bottom, so much the better, 

 as it then is free to give out the heat on all sides. The 

 furnace ought to be not less than eighteen inches wide, and 

 equal height, independent of the arch above, and two feet 

 long. A furnace of these dimensions is qualified to work 

 a house of forty to fifty feet long, by twelve or fourteen 

 feet wide, the flue being conducted along the front and two 

 ends. Double the length will need two fires, and so on in 

 proportion. When two furnaces are required, there may 

 be one placed at each end of the house, and conveyed to 

 the same chimney, midway in the back wall, so as to unite 

 into one outlet ; but in such case there ought to be an 

 acute level upwards at the place of union, or the two 



