172 The Trials of Suction Gas Plants at Derby, 1906. 
coke to burn and also because, just at first, there is a difficulty 
in obtaining a sufficiently inflammable gas (hydrogen). 1 These 
times may be regarded as those likely to obtain in actual 
practical use with coke. 
Smoothness of running . — An estimate was made of the 
comparative smoothness of running, by carefully listening to 
the running of each engine, and by feeling the bearings to 
notice if there was any undue knock. The smoothness of 
running of the valves was also noted. The bearings were 
examined on several occasions after the engines were stopped. 
They were invariably quite cold. An exception, however, 
must be made in the case of the Hindley engine, which was 
running in a closed crank chamber, so that the bearings, and 
in fact all the working parts, were heated by conduction from 
the cylinders ; the bearings were, however, not unduly warm. 
The bearings of the Newton engine, which was also enclosed, 
were not examined. 
Ashes produced . — In some cases the ashes were more or less 
separate from the coal or coke raked out of the producer at the 
end of the run and could be weighed. In other cases they 
were so mixed up with the fuel as to render any separation 
practically hopeless. The matter was not one of great 
moment, however, as the amount of ashes depends more on the 
fuel than on the producer. In this connection a great 
difference was noted as regards the appearance of the fuel that 
came out of the various producers at the end of a run ; in 
some cases it appeared as if it had never been used, in others it 
looked more like cinders full of ashes. This may, however, 
be in great part due to the manner in which the various 
attendants fed in the fuel towards the end of the run ; that is, 
the final condition of the fire and fuel may not have been that 
obtaining during the whole of the trial. 
Clinker . — The quantity and nature of the clinker produced 
was specially observed, because the satisfactory continuous 
running of suction gas plants depends not only on the amount 
of the clinker, but whether it adheres to the firebrick lining 
or not, and whether it comes away easily when raking out 
the ashes, that is, whether the clinker is friable or vitreous. 
As regards the design of the producer, the points noticed in 
this connection were : the manner of supplying water to the 
vaporiser (since the clinker depends on the steam), and the 
shape of the bottom of the furnace and of the grate. An 
estimate of the amount of clinker adhering to the firebrick 
lining was also made. 
1 With anthracite there is a small proportion of volatile hydrocarbons which 
are distilled from the fresh coal and give the inflammable gas required for 
starting. 
