184 TlMEHRl. 
attainable from dry fuel, and the number of units of heat available are 
also less, as will be shown further on. 
It is evident then, the effects of the draught on the heat, and of the 
heat on the draught, must be mutually detrimental ; and considering 
also an estate has to consume at least 2 tons of green megass in the 
place of 1 ton of dried megass, modifications must be introduced in 
the shape and size of the furnace, the distribution of air, the area of the 
flues and the power of the chimney, that involve principles very dif- 
ferent to those now in practice, and about which we probably know 
very little. 
The presence of water, or its constituents, in fuel, promotes the 
formation of smoke, probably by mechanically sweeping along fine 
particles of carbon ; the escape of smoke, so noticeable with the use 
of moist fuel, is therefore due to and indicative of imperfect com- 
bustion. 
I will now endeavour, by means of certain figures, to place the 
matter in a more practical form ; I am however, unfortunate in not 
having with me an analysis of megass, and am presuming the com- 
bustible elements of megass (inclusive of the sugar contained in solu- 
tion before drying) are equivalent to those of wood, pound per pound ; 
this I think will be quite near enough for the comparison to be made 
between more or less dried megass, and will actually be putting the 
megass on too favorable a footing as a fuel. I shall, therefore, substi- 
tute in the following quotations, etc., the word megass for wood. 
In Rankine's " Steam Engine" page 280, 1 find 1 pound of dried megass 
requires 6 pounds of air to effect its complete cumbustion, and if the 
usual allowance be made for the dilution of the gaseous products, we 
have double or 12 pounds of air admitted for every pound of dry megass 
consumed. Now, let us suppose the product's of combustion pass off 
at a temperature of 572 , the volume (page 286) will be 314 cubic feet ; 
if, however, the megass had contained its equal weight of water, there 
would be I pound or about 50 cubic feet of gaseous steam to be got rid 
of besides, or 364 cubic feet. Thus we see the presence of this 1 pound 
of moisture would reduce the admission of air 16 per cent., or necessi- 
ate am enlargement of the flues to the same extent with a proportionate 
increase in the power of the chimney. This, I take it, would not ade- 
quately represent the extent of the evil, for with moisture in the fuel, 
combustion would not be so brisk, the temperature would be less, and the 
draught still further reduced. 
