808 REPORTS ON THE STATE OF SCIENCE.—1913, 
Liquid, Solid, and Gaseous Fuels for Power Production. 
By Professor F. W. Burstauu, M.A. 
[Ordered by the General Committee to be printed in extenso.] 
Tue general problem of power production is one of the most fascinating 
subjects to all engineers, and the author proposes to consider some of 
the means in which carbonaceous substances may be treated to render 
them suitable for the production of power. 3 
The fuel of the world consists of two forms, liquid and solid, both 
of which are closely related, inasmuch as they consist of compounds of 
carbon and hydrogen together with small percentages of other sub- 
stances such as nitrogen. 
To most engineers coal is looked upon purely from the point of 
view of a fuel to use in a furnace for the production of heat. It is, 
however, a complicated substance from which can be extracted a wide 
range of valuable products in addition to its value as a means for the 
production of heat. 
It is often assumed that the oil-engine in one of many forms is 
likely to be the heat-engine of the future, and at first sight there is 
much to be said for this contention. For the heat-engine as a 
thermodynamic machine oil is immensely superior to either solid or 
gaseous fuels because of its high heating value and from the ease in 
which it can be introduced into the working fluid. Putting on one 
side steam for the present, the problem is to heat up a mass of air 
confined in a cylinder. It was soon found by Stirling and many others 
in the early part of the nineteenth century that it was extremely 
difficult to rapidly heat up a mass of air by conduction through a metal 
plate, the only feasible method being to mix the fuel with air and 
ignite inside the cylinder. 
In order to ensure complete and rapid heating up of the air the 
mixture must be as intimate as possible, which is, of course, readily 
and simply obtained with a gaseous fuel, but there are points 
in the use of gaseous fuel which lead to serious  difficul- 
ties. In order to secure efficiency the main mass of the air must be 
heated by compression before the principal heat supply is added; the 
combustible gas may be added before compression begins, as in the 
well-known Otto cycle; but this introduces a possibility of the charge 
igniting before the correct time: it also requires that the gas should 
be free from any liquid or solid substances, a state of affairs not easy 
to obtain on a large scale. If the gas be compressed in a separate 
pump there is a certain loss of heat due to necessary cooling of the 
pump. These inherent defects of the gas-engine will probably prevent 
it ever being made in sizes which approach the steam-turbine. With 
a liquid fuel there is no difficulty in forcing the small amount of oil 
