74 



OBSERVATIONS ON HEATING A PIT. 



the fire, the fuel for which is introduced as before: At the top a and 

 b are two pipes with union joints, giving opening to the boiler at top 

 and bottom. 



N°i 



No. 2. is the chimney detached from the furnace, its only peculiari- 

 ties being a circle of iron, c, nearly as large as the top of the furnace, 

 suspended over the fire, causing the flame to play against the boiler, 

 the draft taking place all round it, and a rim of iron in form like an 

 inverted cone attached at its upper edge to the lid, but leaving a 

 space of about one inch and a half between itself and the circular 

 damper, through which space the draught plays, as shewn by the arrows 

 in No. 1. These two are essential to the working of the furnace with 

 nough of fuel. 



W2 



No. 3. is a ring of iron as broad as the boiler on which it rests, and 

 which is attached to a square iron frame, by which it is fixed in the 

 briuk-work which supports it. The grate G. may either rest on the 



