TRANSACTIONS OF SECTION G. 507 
The ideal position for the works would be about eight miles to the east of 
Johannesburg. Is water available in that vicinity in sufficient quantity to provide 
that required at the price taken in the estimated working expenses? If not, 
where can it be obtained, and at what cost ? f 
Presuming for the purpose of illustration that ample water were available at 
Vereeniging at a distance of, say, thirty-five miles from Johannesburg, an additional 
expenditure of capital of, say, 80,000/. for the construction of a weir dam would 
be necessary. The energy could be transmitted from Vereeniging to Johannesburg 
at 70,000 volts by three sets of transmission lines consisting of three cables each. 
The energy would be received at three sub-stations situated on the west, east, and 
centre of the Rand, and distributed thence as in the case of a central station 
situated on the Rand. 
The total cost of this transmission line and of the additional transformers, &c., 
would amount to 200,0007. On the other hand the outlay of the 300,000/. 
included above to cover the cost of water storage works would be avoided. The 
increased cost owing to the transmission of the energy would be more than com- 
pensated for by the-lower price of the coal and water at Vereeniging, always 
assuming that arrangements could be made for the use of the Vaal River. ; 
If such arrangements could be made the future central power distribution 
station for the Rand will probably be situated there and the supply given at 
O'Gd. per unit. 
In conclusion the writer expressed his great thanks to the engineers and 
managers of the Rand mines who so heartily and fully responded to his requests 
for data as to the present methods. 
2. Water-power Plants. By Etspon Dew. 
3. Dust Fuel. By A. M. Ropeson. 
It is well known that practically perfect combustion can be obtained with 
powdered fuel, and that only the theoretical quantity of oxygen is necessary; in 
fact, the mixture of air and fuel in this form can, for all practical purposes, be 
considered as a ‘gas,’ containing within itself all things necessary-for complete 
combustion. 
A gas which contains within itself all things necessary for complete com- 
bustion is also an explosive mixture, having a definite rate of transmission of the 
point of explosion or ignition for any given conditions of temperature and pressure, 
and this is true of coal dust and air; but fortunately in this case the rate of 
transmission is comparatively slow, and when the volume of mixture in use is 
small, and kept moving, no explosions are possible. It is this difficulty of 
exploding or igniting such a mixture which renders it necessary to surround the 
issuing jet of fuel and air with incandescent bricks, and at the same time is that 
which marks the beginning of the troubles of the experimenter ; for, as would be 
expected, the perfect combustion of a given quantity of fuel with its exact 
chemical equivalent of air in a very short time will result in a maximum tem- 
perature which, together with the powerful slagging action of the dust-ash, soon 
destroys ordinary bricks in the hottest zone and fills the furnace with slag in the 
cooler portions. 
Theoretically the cross-section of the furnace should be altered for every 
change in the rate of firing; but as this is for practical reasons impossible the 
idea cannot be entertained. . . . It will be seen, then, from theoretical considera- 
tion—as is actually borne out in practice—that when powdered fuel is being 
burned in the ordinary manner, z.e., in a straight-through furnace, the conditions 
of quality and quantity of fuel and the amount of air and draught must be 
maintained constant within narrow limits, especially if the coal be_of medium or 
poor quality. 
Tt was the appreciation of the necessity of a furnace which would automatically 
