6o TlMEHRI 
1,700 gallons is water to be evaporated and about 3,000 
lbs. is sugar. But as the diffusion juice is more dilute 
than cane juice, and as steam is consumed in heating as 
well as evaporating, we may take the evaporation of 
2,000 gallons of water as the measure of the coal con- 
sumption per hhd. 
With good modern boilers we evaporate 9 lbs. of 
water per 1ft. of coal actually burnt : but as the weight 
of coal put on the fire-bars is always less than that shown 
on the invoices, and as there are unavoidable losses from 
radiation etc, I think 6 Tbs. of water evaporated from 
the juice per lb of coal paid for, is a reasonable esti- 
mate. The coal consumption is then 20,000 lbs. + 6, or 
say \\ tons. This is with simple effect evaporation ; 
if two-thirds of the evaporation be effected by triple 
effect, whose efficiency is at least double that of the 
simple, and the remaining third by simple eflect in the 
graining pan, the consumption will be 1 ton of coal per 
hhd. 
If I have not made too sanguine an estimate, it would 
seem that the coal consumption alone will not condemn 
the process. 
It is right to mention another possible cause of loss 
of heat peculiar to the diffusion process. In any pro- 
cess the juice must be first brought to the boiling point 
before the water can be evaporated from it : the heat 
necessary to bring it to the boiling point being about 13 
per cent, of that required to effect the evaporation. Now 
if all the vessels of the battery are kept hot, as my own 
observation leads me to think they should be, and the 
cane slices pass out at nearly the boiling point, they 
will take with them an amount of heat equal to that in 
