Report op Society's Meetings. i?i 
*> , „ __„ , , „ „^____ 
to insure good chimney draught, we have for 100 E5s. of sugar contain- 
ing 42* i B5 of carbon and 57*9 lbs of water : — 
42"i x 14,500 H.U.=* 610,450 H.U. minus 
57 - 9 x 1,200 » 69,480 „ 
Remains 540,970 H.U. available 
in 100 Has. of sugar. 540,970 -s- 14,500 = 37'3 0/0 of available carbon in 
sugar. It will be noticed that the total heat of combustion of 1 lb. of 
carbon is taken as 14,500 H.U. This is the result arrived at by MM. 
Favre and Siltermann. Rankine has adopted it in his caculations and 
gives as his reason for doing so : 1st. " The great delicacy and preci- 
sion of the instruments and processes by which this result was ob- 
tained"; and 2nd. " Because amongst a number of different results as 
to the total heat of combustion, the highest is on the whole the most 
likely to be correct, most of the errors being caused by losses of heat. 
Dulong's result is 12,906 H.U., and Despretz's 14,040 H.U 
In order to be able better to compare the compositions of megass, 
obtained with different percentages of crushing, the accompanying 
table * was prepared. The average of the analyses of the canes of diff- 
erent estates given in table A. of Mr. Russell's paper is taken as the 
compositions of the sugar-cane. 
The carbon in the fibre is assumed to be equal to 50 0/0 of the fibre 
and the available carbon of sugar to 37*3 0/0 of the weight of the sugar. 
The figures opposite the heading temperature indicate the elevation 
of the temperature of the products of combustion and the air with 
which they are mixed, at the instant that the combustion is complete 
above the temperature at which the air and fuel are supplied to the fur- 
nace. With fuels containing an excess of water, these temperatures 
can never be obtained, for the reason, that we cannot get the fuel to 
burn and consequently combustion cannot be completed. They are in- 
troduced in the table for the sake of comparison and are used to obtain 
the co-efficients of evaporation, as shall be explained afterwards. In 
comparing different kinds of coal, correct results may be obtained by 
taking the total heat of combustion of their elements in units of heat, 
but when coal is to be compared with green megass, a fuel containing 
a large percentage of moisture, the results, so arrived at, are simply 
misleading. The proof hereof lies at hand. Compare the amount of 
* See page 173. 
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