66 PRACTICAL FLOKICQLTUEE. 



front. This heat, after it leaves the direct action of the 

 fire, when passing again to the front of the boiler, is called 

 " secondary," and though its power is comparatively 

 slight compared with the direct heat from the fuel to the* 

 inner surface, yet it otherwise indirectly benefits, by check- 

 ing the rapid escape of heat out at the chimney, which 

 would be the case to a great extent if this back draft was 

 not used. We believe that by using this second heating 

 surface, a saving of one-third in fuel is made. At present 

 prices, a boiler and pipes to heat 1,000 square feet of glass 

 by hot water will cost in this district about $500. Brick 

 flues, to heat the same area, would cost about $100. 



Heating by tanks of hot water was much in use a few 

 years ago, when the grape vine fever was at its height, 

 and is still used by some for propagating purposes ; 

 but our experience, as well as that of many others who 

 have had them in extensive use, is that they are an un- 

 profitable means of heating. Made in the usual way, of 

 wood, we have never known them to-be in use over two 

 winters without seriously leaking. If made by lining 

 with zinc, or by having them made of cast-iron, they then 

 cost as much as the regular 4-inch pipe, and are not so 

 durable, and for the heating for any purpose they have no 

 advantage in any respect over the pipes. Last year I 

 threw out over 2,000 square feet of wooden tanking, that 

 had leaked so as to become unserviceable in three years, 

 and replaced it by 4-inch pipe. Almost all who have used 

 them have had the same experience. 



