LIQUID, SOLID, AND GASEOUS FUELS FOR POWER PRODUCTION. 811 
transmission, the essential point being to obtain a sufficient supply 
of coal to enable the capital charges being repaid in a series of years, 
probably thirty. 
The works would have to be on a large scale to enable the economy 
of working that always results from wholesale production, but the 
carbonisation plant would be placed near the pithead so that the tubs 
could discharge direct into the bunkers 6f the retort-charging machines. 
A convenient size for each plant would be about two thousand tons 
per day, and there would be some five to six pits operating over quite 
a large area. There would be no gain from any point of view in not 
shipping direct from the pithead the coke and sulphate of ammonia, 
as these would be ready for market without further treatment. 
Tar and gas would be taken by pipe-lines to suitable points for 
their future treatment, depending upon geographical considerations. 
The tar from the whole of the works would be passed through con- 
tinuous automatic stills, where the various fractions would be obtained 
with the least expense. The fractions, after washing with acid and 
soda, would pass to a second set of automatic stills, this process being 
continued until the pure products ready for market were obtained with- 
out the necessity for storage and in the least possible space of time. 
As to how far the treatment of residuals should be carried no 
definite answer can be given, as it depends on the current prices, but 
on the scale considered—120,000 to 140,000 gallons of tar per day—it 
would certainly be advantageous to treat the products to a finish. 
That portion of the gas not required for firing the automatic stills and 
for colliery purposes generally would be led to a different point perhaps 
many miles from the pithead. This offers no difficulty as regards 
the power required, the great obstacle being the cost of the pipe-line. 
This may to a large extent be reduced by gasholders at the delivery 
end so as to improve the load factor on the pipe-line. The gas would 
be free from tar, but would contain the sulphur compounds, and would 
be employed in gas-engines for the generation of electricity, which 
would be sent at high voltages not only to the towns, but for the 
railways which are supposed to be entirely electrified. 
No doubt electrical engineers will look askance at gas-engines, not 
only from the many failures that have occurred with large engines, 
but also at the fact that at present some 2,000 h.p. is the largest 
size that can be built, whereas a steam turbine can be constructed to 
give an output of 20,000 k.w. at a low first cost. The gas-engine 
can only compete with the steam-turbine when its fuel gas is delivered 
to it at a price which will, when helped by its high thermal efficiency, 
enable it to get over its large capital outlay. Perfect as is the steam- 
‘turbine as a mechanical machine, its thermal efficiency is half that of 
its rival; the cost of the steam delivered to it cannot be reduced, as 
the boiler has but a small margin of improvement possible. There 
are no by-products, as the whole of those contained in the coal are used 
to pollute the atmosphere. 
For these reasons it is quite possible for the gas-engine to produce 
current more cheaply than the turbine. The price of gas of a calorific 
value of 500 B.T.U. per cubic foot would have to be about fourpence 
