ON THE MKRITi. OF IKON AND WOOD FOK ROOFS 



foot square, for the convenience of cleaning-out, lighting and 

 making up of the fire the last thing at night ; for it is impossible 

 for any man to manage a fire properly with a furnace door such 

 as are used to some hot water apparatuses that do not exceed six: 

 or eight inches square ; but if a good sized furnace door is used, 

 the gardener is enabled in counties, where coals are dear and 

 wood is cheap, to burn logs of wood or the refuse from the prun- 

 ing of trees, where he only wants a little fire through the day ; 

 but of course it must be understood that this description of fuel 

 is not to be depended on in severe weather, nor for the making 

 up fires for the night. Whatever description of fuel is used, 

 however, I have always found it a great saving to gentlemen to 

 have a moderately large furnace door, great attention being paid 

 to its formation, in order to prevent the passage of air through 

 the door between the boiler and the fire, the neglect of which 

 causes a great waste of caloric or heat, as air will not support 

 combustion until its tempetaturc is raised to 800 or 900 degrees 

 of Farenheit, therefore a current of cold air admitted between the 

 boiler and fire through the door, has a tendency to counteract the 

 power of the fire ; to obviate which double doors should invariably 

 be used, and then if the boiler is so constructed and set as to 

 expose (which is the great secret in the formation of all boilers) 

 a large surface to the action of the fire by means of the construc- 

 tion of the flues round it in such a way as entirely to consume the 

 whole of the caloric or heat before it escapes into the chimney, 

 the greater will be the saving of fuel, and the more powerful and 

 effective the operations of the apparatus altogether. Indeed I have 

 no hesitation in saying if a proper quantity of pipe is used so as 

 to give a sufficient quantity of surface for the command of tem- 

 perature required in all extremes of weather ; and the furnace, 

 boiler, and flues, being so constructed as suggested, the fire might 

 be made up and left without the least risk for six or eight hours 

 on the severest nights. In the formation of the Egg Shaped 

 Boiler my attention was particularly devoted to the construction 

 of a furnace that would obviate the evils complained of in most 

 hot water apparatuses. I mean the great consumption of fuel 

 and the almost constant attention required, all of which arises 

 from badly constructed fire places and boilers ; but, then on 

 si \ ral other circumstances connected with hot water apparatuses 

 h I think highly nccessai) to be attended to, particularly 

 where the boilers arc formi d of i eries of pipes; varying from half 



