By Thomas Andrew Knight, Esq. 157 



The quantity of coal dust consumed during the coldest wea- 

 ther of the last winter was between seventy and eighty pounds 

 weight in every twenty-four hours ; and I consider the ag- 

 gregate expense to have been about seven-pence a day, the 

 price of the coal dust delivered being ten shillings per ton, 

 and the value of the burnt earth, as manure, being fully 

 equal to the expense of the preparation. Newcastle coals 

 would consume much more slowly, and, in an equally quick 

 draft, would probably admit the mixture of a larger propor- 

 tion of earth. It is scarcely necessary to add, that the 

 foregoing practice will be found most advantageous, where 

 the price of coals is highest. 



The fire in my hot-house, in the most severe weather of 

 the last winter, was constantly made up for the night before 

 five o'clock in the evening, and it was never again visited 

 till seven o'clock the next morning, when it was always found 

 in a state to afford fully sufficient heat to the house, which 

 is forty feet long by twelve wide, and heated by a single fire. 

 But it sometimes happened, after a windy night, that the 

 structure of the masses of clay and coal had been wholly 

 destroyed ; and in such case, when the weather was very 

 severe, it was found expedient to introduce a small quantity 

 of faggot wood, or decayed pea sticks, between the ignited 

 mass and the fuel put on in the morning 



It will probably, at first view, be thought that the clay 

 or pond mud, in the case above stated, operated beneficially 

 in no other way than by preventing the too rapid combustion 

 of the coal; but I believe that it executes a much more 

 important office. It is well known in countries where wood 

 is chiefly used as fuel, that a mixture of dry and green wood 



