158 Transactions of the Society. 
alterations in the running conditions of the particular plant made 
necessary by the use of a different coal, and to issue instructions 
beforehand for any change in the working of the coal. This elimin- 
ated difficulties which would otherwise have arisen. Had the type 
of coal not been known any adverse effects could only have been 
combated as they arose. In some cases this would have meant 
delays for twelve to twenty-four hours after the coal had been 
put on. It might even have meant partial stoppage and a con- 
sequent drop in production, etc. So far I have attempted to 
show you something of the selection and allocation work of a 
fuel department in a large industrial works, where many classes 
of coal are in use for a variety of purposes. I have described 
for you these coals and the uses to which they should be put. 
I have also shown you how successful fuel selection can be 
made when a knowledge of the microstructure of the coal is used 
to supplement the information given by chemical analysis. I 
hope I have been able to convey to you some idea of the value 
of the microscope for this work when in the hands of an experi- 
enced technologist. I would now like to point out to you other 
uses to which the microscope can be put which are of considerable 
interest to industry. Of special interest commercially is the iden- 
tification of the various coal constituents. Little is known as 
yet of the influence of varying amounts of the different constituents 
in a coal. I have briefly referred to the nature of some constituents, 
but it is more in regard to the nature of the resulting bye-products 
from coal-distillation that the microscopic study would be helpful. 
This question of bye-products has been studied extensively from 
the chemical side, which study tends to show that temperature 
plays a most important part in the nature of the bye-products. 
Two recent examples of chemical work might be quoted. Pictet 
and his co-workers have published some very suggestive work 
on the distillation of coal in vacuo. They show that the coal 
substance breaks down with the formation of alcohols and the 
cyclic paraffins, and that the more valuable aromatic compounds — 
namely, benzene homologues — are formed from these at a 
higher temperature (Pictet : Rev. Gen. des Sec., Oct. 1916, 
Yol. XXVII.) 
The control of temperature is of great importance in coke 
manufacture. S. Roy Illingworth (J. Soc. Chem. Ind. Trans., Yol. 
XXXIX., Nos. 9 and 10) shows that it is possible to make a metal- 
lurgical coke from, an apparently unsuitable coal by controlling the 
temperature. He also shows that it is varying amounts and 
differences in the coal constituents which cause changes in the 
behaviour of a coal. It will be realized that this kind of work is 
of great importance, but it gives no idea of the reasons why coals 
should vary to such an extent. It is in this connexion that I 
think a detailed microscopic study is vitally necessary. There is 
