THE CULTURE OF THE GRAPE. 39 



rapid when the boiler contains but a small quantity of 

 water, provided the pipes are always full, which they 

 must be. But it is essential for a rapid circulation that 

 ample distance be allowed between the pipes, which may 

 be from four to six inches in diameter ; the lower one 

 should be arranged first, and supported and kept in place 

 on a perfect level, by brick or stone. Above this, should 

 be the upper and warmest one, properly levelled and ar- 

 ranged. You may place the pipes on either side of the 

 furnace, but the side next the front of the house is usually 

 the one considered best ; I would recommend four to six 

 inches for the space between them. I have in my 

 houses, at the extreme end, a tank containing thirtj'- gal- 

 lons or more of water, to wliich the pipes are attached, 

 in the same manner as to the boiler ; but this is not ne- 

 cessaryj though preferable. The pipes may connect at 

 the end by an elbow, and they work equally well ; but a 

 tank at this place with a quantity of water, which be- 

 comes heated, is of service, as this is the coldest part of 

 the house. An opening must be provided on the top of 

 the boiler, or tank to fill these with the water. 



THE POLMAISE SYSTEM OF HEATING. 



Much discussion has been held of late in England, rel- 

 ative to this mode of heating green and other houses for 

 horticultural purposes, and some curiosity has been exci- 

 ted in this country as to what the system is. The princi- 

 ple is similar to that upon which many of our churches 

 and dwelling-houses have, for many years, been warmed. 



