518 Notices of Memoirs—Disecussion on Coal. 
of the coals. He thought that all geologists would recognize the 
importance of the results which have been already obtained by the 
study of the behaviour of coals when extracted with various solvents. 
He had himself come up against some of the technical difficulties 
mentioned in the paper by Drs. Wheeler & Stopes, which 
invalidate the results which might be expected from the direct 
extraction of transparent micro-preparations of coal with pyridine or 
chloroform, but from his own experiments he was led to expect that 
the methods of the metallographer, applied to cleat surfaces or 
polished specimens of coal etched with these solvents, may provide 
the information which is immediately required. He wished to 
support Dr. Hickling’s contention that whenever a chemical analysis 
of a sound block of coal is undertaken, opportunity should be given 
for the paleobotanists to ascertain the microscopic structure of 
a corresponding portion of that same piece of coal. He expressed 
the opinion that great mutual advantage would accrue if the chemists 
would co-operate with field- geologists and mine workers in the 
choosing of the samples of coal which are worthy of analysis. He 
suggested in particular that one of the directions in which this 
co-operation between chemists and geologists was most to be desired 
was to secure a real knowledge of the lateral variations of composition 
within the individual lenticles of coal, which in sum constitute the 
wide-spreading beds of rock which are known as coal-seams. 
Professor Boyd Dawkins emphasized the point raised by Dr. Hickling 
that the apparent identity in structure of certain parts of the coal 
with the cell-structure of the living plant does not necessarily prove 
that the original tissues of the plants have been preserved. It is 
a matter of common geological knowledge that very generally in the 
process of fossilization the original tissues, both of plants and animals, 
have been replaced atom by atom by carbonate of lime or silica, or 
even iron pyrites, without the details of structure having been 
destroyed. Sometimes, as in the case of the deposit of calcite in 
wooden troughs in coal-pits, the structure of the wood, including the 
growth-lines and medullary rays, is faithfully reproduced. In 
specimens in the Manchester Museum the calcite cast of the interior 
of sea-urchins, from the Coral Rag, has carried the pattern of. the 
test into the very centre, as the mineral slowly filtered through the 
wall. This point must be considered by the paleobotanists, who are 
doing their share of work in dealing with the history of coal. In his 
opinion the greater part, if not the whole, of the organic element in 
the coal had been subjected to mineral change. 
Professor W. S. Boulton (who presided) expressed his gratification 
at the opportunity for an interchange of ideas among chemists and 
geologists upon a subject of vital importance to thenation. Already, 
much valuable research upon the nature and composition of coal had 
been done, both on the analytical and on the microscopical and palzo- 
botanical side. He felt sure that when the printed records of the 
discussion were published, they would serve to stimulate to fresh and 
more vigorous research, and more especially to co-ordinate and 
mutually assist the work of the chemist and geologist, and so 
enormously increase the value of our greatest industrial asset. 
