ON THE MERITS OF IRON AND WOOD FOR ROOFS. 55 



succeeded in saving the second house of fruit, but not without 

 great injury to the foliage ; this misfortune and unavoidable cir- 

 cumstance was generally known in the neighbourhood of Seven- 

 oaks, and observed by many practical gardeners, who can vouch 

 for the accuracy of this statement. 



Agreeable to your request I have forwarded the description of 

 the boilers, which I trust you will receive safe. Figures 1, 2, 3, 

 and 4, is intended for bouses of small dimensions, and the large 

 one, figure 5 for extensive houses : this, as well as the other 

 boiler is oval-shaped, and would be sufficient to heat seven or 

 800 feet of four-inch pipe at a triffling expense, for during the 

 severest part of last winter, all the houses I have heated with 

 this plan of boiler, were kept up to their respective tempera- 

 tures, without burning a bushel of coals, the only fuel used was 

 small coke, and during the intense frost of Friday night Jan. 

 19th last, when the thermometer stood at a quarter past 6 o'clock 

 in the morning, at 12 degrees below Zero, we had not the least 

 difficulty with keeping every house, both stoves and greenhouses 

 at their respective temperatures. I have devoted much time 

 and attention to heating houses with hot water for several years 

 but more particularly last season, and this winter up to the pre- 

 sent time, and from accurate calculations made of the number 

 of feet of surface of glass exposed to the action of the weather 

 1 am enabled from watching the thermometer, both out of doors 

 and in the houses, with all extremes of weather, to calculate most 

 correctly the number of feet of surface of pipe required to com- 

 mand (even with 42 degrees of frost) any given degree of heat 

 required for stoves, greenhouses, and other buildings, and the 

 want of this practical knowledge, and attention to this highly 

 important part, (the radiating surface) has been the cause of so 

 many complaints against the system ofheating by the circumvo- 

 lution of hot water, all of which would have heen prevented 

 had the hot water fixer devoted a few nights during the severe 

 frosty weather to this indispensably necessary calculations, but 

 then his remarks should not have rested on the obs^ervationsmade 

 during a calm night of severe frost. I have found by sitting up 

 to watch the thermometer for whole nights together, that a 16 

 degree's of frost, with a strong wind, is more trying to a house 



