26 ' Of the Management of Fire 



larger end or base ; and 5^ inches in diameter inter- 

 nally, and 7$ inches in diameter externally, at its smaller 

 end ; and being firmly fixed, with its axis in a hori- 

 zontal position, and its larger end or base outwards, in 

 the middle of the opening leading to the fire-place, and 

 being well united with the solid brick-work by means 

 of mortar, the cavity of this cone formed the opening 

 by which the wood was introduced into the fire-place. 

 This cavity being closed with a fit stopper of earthen 

 ware, as earthen ware is a non-conductor of heat, or as 

 heat cannot pass through it but with great difficulty 

 and very slowly, the external surface of this cone and its 

 stopper were never much heated, consequently the quan- 

 tity of heat they could communicate to the atmosphere 

 was but very trifling. This contrivance was afterwards 

 rendered much more simple by substituting, instead of the 

 hollow cone, a tile, 10 inches square, and about 2% inches 

 thick, with a conical hole in its centre, 6 inches in diam- 

 eter externally, and 5! inches in diameter within, pro- 

 vided with a fit baked earthen stopper. (See the Figures 

 No. 6, 7, and 8, Plate I.) 



A perforated square tile is preferable to a hollow cylin- 

 der for forming a passage into the fire-place, not only 

 because it is cheaper, stronger, and more durable, but 

 also because it may, on account of its form, be more 

 easily and more firmly fixed in its place, and united with 

 the rest of the brick-work. 



If proper moulds be provided for forming these per- 

 forated tiles and their stdppers, they may be afforded for 

 a mere trifle. In Munich they are made of the very best 

 earth, by the Elector's potter ; and they cost no more than 

 24 kreutzers, or something less than <^d. sterling, for a 

 tile with its stopper. I had several made of sandstone 



