386 Dr. W. J. Russell. The Action of Resin and [Mar. 24, 
but if the coal was exposed to the air for 24 hours its activity considerably 
decreased, but was restored by again placing it over sulphuric acid. 
Coals exposed to sunlight or are light do not perceptibly increase in 
activity, as many other bodies do, nor does the small amount of substance 
dissolved out of them by boiling alcohol appear to be active. 
The following pictures are fair samples of coals from different English 
beds: figs. 7 and 8 (Plate 12) are both from South Wales. Fig. 9 is a 
Nottingham coal, fig. 10 a Derbyshire one, and fig. 11 is from Lancashire. In 
all cases the deposit of vegetable matter in long or short strips or patches is 
clearly shown and well defined, and the presence of vegetable matter appears 
diffused through the mass of the coal. 
Although there must necessarily be a strong resemblance between coal 
pictures, still it may prove that a certain specific and recognisable character 
belongs to coals from different beds. For instance, judging from the few 
specimens which have been examined, the South Wales coals appear to have 
their active strata fine and near together, whereas the coal from Derby and 
Nottingham has active strata which are much thicker and very sharply 
defined; but considering the small number of experiments made, this may 
be purely accidental. The pictures, however, clearly show differences in 
coals ; for instance, all the anthracites that have been examined have given 
pictures different from the foregoing: they are fainter in appearance, the 
structure they represent is more complicated and the active matter more 
evenly distributed through the mass of the coal, as shown in fig. 12. There 
always appear to be cracks in anthracites and these cracks are always white. 
There is also another curious point with anthracites: if they are dried over 
sulphuric acid the picture they give is much darker than the picture obtained 
in the ordinary way, fig. 13. Only a few Cannel coals have been examined : 
these gave pictures in character like the anthracites but with less detail 
and not so dark. Fig. 14 is a picture of the well-known Boghead Cannel 
coal. 
From coal plants of different kinds and from different localities no 
pictures have been obtained. If the soft powder so common in bituminous 
coals and known as “ Mother of Coal” is carefully removed and tested it is 
always found to be very active. The large amount of diffused action on the 
top of fig. 4 is owing to this substance; also the fibrous substance so often 
present and easily removed from coal is also very active, but the hard 
glistening surface of coal is only slightly active. Of the coals which have 
been examined, a Boora coal from the Lower Oolite, a Jurassic coal from 
Mexico, and some Argentine coals and a Tertiary coal from India are ones 
which have been found to have little or no action on the photo plate. No 
