810 REPORTS ON THE STATE OF SCIENCE.—1913, 
apply only partially ; the steam generation of power is familiar to all, 
80 the various forms of gas production need only be touched upon. 
Gas power can be obtained in the following ways: 
1. Town gas, made in closed retorts. 
2. Producer gas, made by blowing air and steam into incandescent 
fuel. 
3. Gas from coke ovens, where the production of hard coke is the 
primary end. 
From one ton of coal gasified in a modern gasworks are obtained 
11,500 to 12,506 cubic feet of gas having a calorific value of about 
550 B.T.U. per cubic foot, about ten gallons of tar, and 25 to 30 lb. 
of sulphate of ammonia. The gas has to be purified for domestic 
purposes. Also a gasworks has to be near a great town, where the 
working expenses are not so low as in a more rural part. For these 
reasons it is doubtful if town gas can be supplied under present 
conditions for much under tenpence per thousand cubic feet. 
A good gas-engine and dynamo will give one kilowatt hour for 
20 cubic feet of gas—that is, at a fuel cost of 0.2d. per kilowatt hour, 
which, of course, is too high for large-sized units. 
Despite these facts the author is of opinion, after mature con- 
sideration, that the whole problem of fuel treatment will lie in the 
direction of heating the coal, peat, or lignite in a closed retort—not of 
necessity under the conditions which are at present forced on to the 
gasworks, where the primary object is to produce the largest yield of 
gas on a certain standard laid down by Parliament. 
If it be granted that the quantity, quality, and purity of the gas 
produced are a secondary matter, the problem of fuel treatment becomes 
one of the most fascinating problems which the engineer can encounter. 
It has long been known that the quantity and quality of the tar are 
largely influenced by the temperature at which the fuel is carbonised: 
the lower the temperature the better are the tars in both yield and 
composition. The amount of sulphate of ammonia recovered from the 
gas is only some 25-30 lb. per ton of coal, whereas the amount of 
nitrogen present in the coal would give about 120 lb. of sulphate of 
ammonia. In the ordinary process of carbonisation some three-quarters 
of the nitrogen is left behind in the coke. Under present conditions 
this cannot be avoided, but improvements in this direction are possible. 
If the gas and tars are withdrawn from the heat directly they are 
evolved from the coal a set of products will be obtained of a different 
composition from those usually found in gasworks tar. Many of these 
oils can, after distillation, be employed as fuel oils for power produc- 
tion, both the light oils, such as benzole, pentane and hexane, and 
middle oils, such as cresylic acid, while the heavy oils of the anthra- 
cene series appear to be of value for lubricating purposes. 
The author trusts that an engineering audience will pardon him 
for outlining a scheme of fuel treatment which is at present wholly 
beyond the region of practical realisation. The first step is to obtain a 
coalfield of wide extent yielding a coking coal. It need not be within 
a short distance of towns, as that will merely modify the means of 
