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176 Reviews—Memoirs of the Geological Survey. 
The second chapter consists of a lithological description of the 
rocks not of the Coal-measures only, but of the underlying Millstone 
Grit, Yoredale Rocks, and Carboniferous Limestone; by far the 
greater number of the 469 pages of which it is composed being 
devoted to the Coal-measures. It is of course utterly impossible to 
attempt any abstract of it; the mere table of contents would occupy 
more space than could here be spared. 
Among other matters the rapidity with which the sandstones 
thicken and thin away is here noted. “Cases will be given where 
sandstones run with a fairly regular thickness of 100 feet or more 
over miles of country, and then wedge out to nothing in a space of 
half a mile or less.” And their irregularity in composition or 
grain is noticed, together with the probable circumstances attending 
their deposition, which account for it. The existence in the coarser 
sandstones of lumps, and even crystals of orthoclase, only slightly 
decomposed, often gives the rock quite a granitic look, and may 
have been, the editor remarks in a note, the resemblance which 
led Charlotte Bronté into the mistake of describing the rocks of her 
native moors as granite. 
The shales or binds also vary indefinitely, in composition, from 
those known as stone-bind or rock-bind, which may be called either 
sandy shales or shaly sandstones, to the purely argillaceous blue and 
soft binds. And these last are often darkened by the admixture of 
organic matter, till in some cases they become black, and pass by a 
gradual increase in the proportion of vegetable matter into impure 
cannel coals. These cannel coals are considered by Prof. Green to 
be exceptions to the rule that “the majority of the coals we have 
to deal with were certainly land-growths.” He thinks that they, 
on the contrary, were formed under water, the plants of which they 
are composed having drifted into shallow ponds or lakes. 
Before coming to the Coal-measures, the Millstone Grit is briefly 
dealt with, the circumstances of its deposition, and its local varia- 
tions being noted. A general sketch of the Coal-measures precedes 
the detailed account, a course which renders the latter much more 
digestible. 
The Lower Coal-measures, or beds between the Rough Rock and 
the Silkstone Coal, are intermediate in character between the Mill- 
stone Grit and Middle Coal-measures. Their sandstones are more 
massive, and their coals thinner than those of the latter. One rock, 
and one only, the Elland Flagstone or Greenmoor Rock, which 
belongs to the Lower Coal-measures, is traceable throughout the 
Coal-field, and makes therefore an excellent horizon. 
The lowest bed of the Middle Coal-measures, the Silkstone Coal, is 
perhaps the most important of all the coals, the next in consequence 
being the Barnsley. The coals, though, on the average, much more 
persistent than the sandstones, vary considerably from place to place, 
and not unfrequently die away altogether. Both the Silkstone and 
Barnsley coals are traceable over the greater part of the Coal-field, 
and where they exist none others are worked. The tendency is there- 
fore to avoid sinking pits at spots where there is any great thickness 
