192 TlMEHRI. 
a good round sum of money, I have heard that it was very unsuccessful, 
for after everything possible had been done to make the water ascend, 
" the thrawn thing wad gang its ain way." Very much the same thing 
has been done in the present instance. Many attempts have been made, 
and at considerable expense to extract from wet fuel what is really not 
there. The paper before us shows conclusively that the value of megass 
as a fuel is very nearly in proportion to its dryness, and that any 
attempts that have as yet been made to make it yield fire from the 
water contained in it must necessarily result in failure. 
Besides the truths so clearly enunciated in the paper, there is one of 
not less importance which seems to have been omitted. It is this ; fuel 
consumed at a low temperature will not communicate the same amount 
to a steam boiler as if the same fuel had been consumed at a high 
temperature. Professor Rankin puts it thus, " when the difference 
between the heat of the gases and the water to be evaporated is very 
great, the rate of conduction increases faster than the simple ratio of 
that difference and is nearly proportional to the square of the differ- 
ence of temperature." If inventors had been aware of this law, or if 
they had kept it steadily in view, it might have kept them from 
deluding their customers by promising reductions in fuel varying from 
15 to 60 per cent. To illustrate how this law operates, let us assume 
that the gases given off from a furnace where wet megass is used as 
fuel reach the boiler at a temperature of 1300 degrees Fah., although I 
doubt very much if they are ever so high, while those from a furnace 
where dry fuel is used are 1800 degrees ; they are often more than 
this. The temperature of the water in the boiler is in both cases 300 
degrees Fah. ; the rate of conduction in the one case is then to the rate 
.of conduction in the other as (i300° = 300°) (i8oo°=300°), or as 1 : 
2"25- Thus it will be seen that however much you may increase the 
volume of heated gases by increasing the size of furnace and grate area, 
unless you can at the same time increase their temperature, very little 
more heat will be communicated to the water in the boiler. The capa- 
city of water vapor for heat is so great that it is impossible by any of the 
methods yet proposed to obtain a high temperature from a fuel which 
contains two-thirds of its weight of water. 
The history of wet megass furnaces is very interesting and rather 
curious. My attention was first directed to the subject in 1880, by the 
report of an eminent planter who went to Martinique to report on the 
Marie Furnace at work there. In that report he says, " with regard to 
