Discussion on Coal. Ss 
third, the sparry snbstances, generally calcite or iron pyrites, 
segregated as velnsin the seams. The ordinary method of making 
an analysis for commercial purposes would not, of course, dis- 
criminate between these. A certain weight of coal was taken as 
nearly as possible representative of the whole seam, and after being 
broken into small particles was sampled and the fraction analysed. 
This gave no details as to the location of the respective types. 
of ash, observation upon the seam under ground, or of the coal as 
marketed, nor showed how the sparry material was disposed in the 
‘cleat’ or system of joints traversing bituminous coal. The work 
done in Neweastle by Dr. Garrett and the late Mr. Burton, who 
obtained radiographs of slices of coal, promised results of great 
interest; other means were also available. It is well known that 
ordinary coal consists of alternating bright and dull layers, and the 
late Professor A. H. Green obtained separate analyses of these two 
types, showing that the bright layers yield a very low ash percentage, 
while the dull charcoal layers may contain a much higher proportion. 
This has been confirmed by general experience. Another method 
employed for the purpose of deciding whether a coal would be 
improved by washing was to crush it down to fine granules, ~4;in. 
in diameter, and separate by specific gravity into moieties respectively 
of 1:2-1°3 and 1:3-1°4. The former in cases cited proved to be 
bright and lustrous, and to have an ash content amounting to only 
one-fifth of that found in the heavier sample, which was of a dull 
aspect. The inference has been drawn from the very low ash 
content of anthracite that it was composed of a different assemblage of 
plants from those producing the more bituminous seams or parts of 
the same seam. ‘The speaker demurred to this, and pointed out that 
low ash is not a universal characteristic of anthracites, but also that 
two features of anthracite seams combined to give a low ash, the 
dull layers are generally of very small dimensions, and anthracite, 
the world over, is destitute of ‘cleat’. The contention that the 
sparry infilling of ‘cleat’ crevices in bituminous coal is derived from 
the coal, seems contradicted by its composition—the high percentage 
of calcium carbonate and of iron and low potash in the ash taken as 
a whole is the reverse of what would be found in any average 
assemblage of plants, and the speaker would regard the lime and the 
iron as introduced bp pereolation from the measures. It is much to 
be desired that geologists, chemists, and paleobotanists should combine 
to make exhaustive studies of a seam from floor to roof, and also to 
extend their scrutiny to the variations of a given. seam from place 
to place, so that such anomalies could be explained as that of 
a well-known seam in Yorkshire that in two adjacent pits passes 
from a ‘ coking’ to a ‘non-coking’ condition. 
Dr. Dunn thought the discussion showed the need of co-operation 
and collaboration, not only of the chemical workers, as suggested by 
Dr. Bone, but of geologists and botanists with the chemists. Professor 
Lebour had blamed the chemists for not furnishing a philosophical 
classification of coals; but classification depended partly on the 
purpose to be served by it, and partly on the extent of our knowledge 
of the things to be classified. Such classifications as had been 
DECADE VI.—VOL. I1.—NO. XI. 33 
