812 REPORTS ON THE STATE OF SOIENCE.—1913. 
per thousand cubic feet. If coal be taken as twenty shillings per ton, 
this will give for each fuel about 125,000 B.T.U. per penny. Taking 
the gas-engine as two and a half times as efficient as the turbine, this 
ace leave enough margin to compensate for the increased capital 
outlay. 
The exhaust gases would be washed so as to extract the sulphuric 
acid, which would be returned to the pithead for the manufacture of 
sulphate and the washing of the tars, so that all the external material 
to be purchased is the soda ash used to neutralise the excess acid. 
In this manner the whole of the products of the coal would be recovered 
in a form ready for the market, and if the coke were used as a 
domestic fuel a smoke-laden atmosphere would be impossible. 
Producer-gas for power and heating purposes has a large field in 
front of it, particularly when the factory is widely distant from the 
coalfield, and also where there is steady load of large amount, such 
as electrolytic production. 
In producer-gas the whole of the fuel is converted into gas and tar 
so that a large quantity of gas (120,000 to 140,000 cubic feet) can be 
obtained per ton of coal; the ammonia yield is very high, being from 
80 to 90 Ib. of sulphate per ton; the calorific value of the gas is low, 
about 140 B.T.U. per cubic foot; and the tar is small in quantity 
and poor in quality, as it is nearly all pitch. 
The low galorific value and the difficulty of cleaning the gas are 
serious drawbacks to the transmission over long distances. In South 
Staffordshire producer-gas has been piped over a wide area for several 
years, and the undertaking now appears to be on sound financial ground. 
The suction producer working on coke or anthracite coal has a very 
definite position for small plants in remote districts, where it forms a 
cheap and reliable source of power. 
The propulsion of ships by internal-combustion engines is one of 
the most important problems of the near future; the gas-engine itself 
offers no special difficulty, but to instal a producer plant of large size 
does not appear to the author to be possible for the following reasons: 
The space taken by the producers alone is large, and in addition there 
is the cleaning plant. Again, when the percentage of the poisonous 
carbon-monoxide is high, 15 per cent. to 20 per cent., the plant should 
be entirely in the open air to prevent the risk of gassing. These 
conditions are most difficult to fulfil, and now that the Diesel motor 
has proved itself to be suitable for marine propulsion the more cumber- 
some and dangerous producer will be discarded. 
Taking the question of producer-gas as a whole it would seem as 
if it will always have a definite use but only a limited application, 
more especially in a country like Great Britain, where in time it will 
be possible in almost every part to obtain electricity cheaply in bulk. 
When this is the case no other source of power need be considered. 
The case of coke ovens really falls into the same class as the 
retorted gas, the only difference being that to obtain a coke capable 
of carrying the weight of the iron in the blast furnace the temperature 
of carbonisation must be high (1,200° C.) and the period long—twenty- 
four to thirty hours. Thus the tars are poorer from being more split up, 
