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XXIII. On the most economical Method of employing Fuel 

 in heating the Flues of Forcing Houses. By Thomas 

 Andrew Knight, Esq. F. R. S.$c. President. 



Read May % 1820. 



Jn cultivating the Pine Apple without the aid of any other 

 artificial heat than that derived from the flues, I have endea- 

 voured to ascertain by what means a high and regular tem- 

 perature can be best maintained with the least consumption 

 of fuel, and expense of attendance : and I have succeeded so 

 well, by the following method, that I think I can with confi- 

 dence recommend it. 



I caused coal, in a state of dust, and of a kind which does 

 not unite when heated, to be incorporated, when very wet, 

 with about one-third of its bulk of clay, or pond mud ; and 

 this composition, after being firmly beaten together upon a 

 broad flat stone, or board, to the requisite degree of thickness, 

 was cut into square pieces of the size and form of half a com- 

 mon brick. A fire grate of the usual form, but of large size 

 (about two feet square) was prepared to receive it, it being 

 expedient that the fire place should contain a large mass of 

 materials of slow combustion : and as the coal dust, in the wet 

 state, above mentioned, does not readily ignite, a sufficient 

 quantity of wood to make a moderately strong fire was pre- 

 viously introduced. The masses of clay and coal dust were 

 then put in by means of a small iron plate with a long handle, 

 and no other material has subsequently been found necessary. 



