Discussion on Coal. 515 
cellulosic and resinic portions. The cellulosic derivatives contain 
compounds the molecules of which possess the furan structure and 
yield phenols when destructively distilled. There are also compounds 
present the molecules of which have structures resembling that of the 
carbon molecule, but it is unlikely that ‘free’ carbon is present in 
coal. The cellulosic derivatives are probably few in type. The 
resinic derivatives contain compounds in which alkyl, naphthene, and 
unsaturated hydroaromatic radicles are attached to larger and more 
complex groupings. It is doubtful whether aromatic groupings are 
present. Under the influence of pressure the bulk of the resinic 
derivatives have become highly polymerized. The oxygenated resinic 
derivatives are chiefly oxides, probably cyclic oxides; esters, lactones, 
anhydrides, acids, and ketones are absent or present only in small 
quantity. Hydrocarbons exist in the resinic portion of coal; saturated 
hydrocarbons (paraffins) are, however, present in small quantities only. 
Dr. Marie ©. Stopes, who had also been working in conjunction 
with Dr. Wheeler, said that in dealing with the composition of coal 
the chemist is faced with the difficulty that there are contained in it 
a number of different compounds which must be separated from one 
another before their characters can be determined. ‘The only clue to 
their composition is the fact (no longer seriously disputable) that they 
are of vegetable origin. In estimating the nature of coal unaltered 
by heat or chemical action, up to date the chemist has done no more 
than, by means of solvents, roughly to separate coal into two main 
classes of constituents which have been termed ‘cellulosic’ and 
‘resinic’. Of these the ‘cellulosic’ constituents are separable into 
two groups. Palobotany has established the fact that some, if not 
all, ordinary bituminous coals are formed from a mixture of various 
parts of land-plants.1 No living plant is so simply divisible into 
two constituents as is coal into ‘cellulosic’ and ‘resinic’; cellulose 
forms the major part of the cell-walls of the soft tissues, resin may 
be present in special cells or glands, and may possibly be modified 
from various cell contents, but the different portions of even the 
simplest land-plant are composed of a great variety of distinct chemical 
compounds, many of which have been named and classified by plant- 
physiologists. Though a number of these substances may be but 
slight variations of the ‘cellulose’ complex molecule, yet in the 
living plant they have distinctive work to do and have recognizably 
various morphological and physical properties. It is not unnatural 
to assume, therefore, that these various substances may be the sources 
of different chemical compounds now in coal. It will be readily 
understood that were different by-products from coal traceable to 
specific parts of plants, and these plant-remains were visually 
recognizable in the coal itself, a considerable step might be made in 
our knowledge of coals and their potentialities. For the individual 
plant portions might be isolated by suitable methods, and the 
substances for which they were responsible when coal is heated 
determined. (This is not invalidated by the fact that these portions 
may or may not differ in composition from the corresponding parts of 
living plants.) It is on such work that we are at present engaged, 
1 Though this is widely accepted it has been proved in very few cases. 
