Microstructure of Coal from an Industrial Standpoint. 153 
not be uniform. Some portions would undergo fairly rapid decay, 
while others would be covered and protected from bacterial and 
other actions, so that we might expect to find plant remains which 
are but slightly altered. These remains might, perhaps, be broken 
up, but not necessarily much altered in composition. The micro- 
scope, in fact, shows but slightly altered plant tissues, and various 
workers seem to agree that it is possible to dissolve out small 
amounts of cellulose from some coals. Cellulose contains a high 
proportion of oxygen and hydrogen in its molecule ; and a small 
proportion of only slightly altered cellulose tissue in a coal will 
have a very marked influence on the ultimate analysis. It follows, 
then, that two coals which are composed of similar vegetable 
remains, may have very different ultimate compositions, without 
being very dissimilar in their general properties. In practice this 
is found to be so. I would repeat, it is not so much in accordance 
with the carbon, hydrogen and oxygen content that coals vary, but 
rather with the proportion and type of the different substances in 
the coal conglomerate. Chemical classifications do not take these 
points into consideration, and by chemical analysis, so far, it has 
not been possible to identify satisfactorily the various coal sub- 
stances. 
By far the greater part of the coal found in this country is 
classified by the usual chemical methods as “ bituminous.” The 
chief exceptions are the anthracitic coals of South Wales. It is 
with these so-called “ bituminous ” coals only that I intend to deal ; 
so far as I am aware no really satisfactory sections of the anthra- 
citic coals have been prepared. The “ bituminous ” coals are of 
great industrial importance, and consequently numerous attempts 
have been made to group them according to their behaviour when 
in use. It is obvious to even the most casual observer that there 
are great differences in coals when burnt, say, in an open grate. 
Some are fragile and ignite readily ; others are very hard and 
difficult to ignite ; some swell up and coke; while others burn 
away to ash without any formation of coke. Some coals burn with 
a long flame, others with a short one. Hence we get such terms 
as “dry coals,” “ fat coals,” “ lean coals,” “ long and short flaming- 
coals,” etc. Bone, in his book on “ Coal and its Scientific Use,” 
gives a modification of the Begnault Griiner classification (which 
is one of the earliest, and is based on the oxygen-carbon ratio of 
the coal — a most unsatisfactory method). The “ bituminous ” coals 
are divided into non-coking long flame, coking long flame, hard 
coking, and hard coking short flame. 
Bone remarks, “ The author’s own .investigations on typical 
English coals have brought to light some interesting examples of 
coals possessing quite different properties whose elementary com- 
positions are very similar.” 
I have examined over two hundred different coals in the last 
