BRITISH ASSOCIATION MEETING AT NEWCASTLE. 
3G5 
acts, to demand attention and concentrate our interest. The carboniferous 
system is commonly divided, for convenience' sake, and in accordance with 
the structure of most European coal-fields, into three principal divisions, 
viz. the carboniferous limestone, the millstone grit, and the coal-measures. 
I need here say nothing of the Devonian or Old Ived Sandstone system, 
or of the still older rocks, which in the absence of the Devonian form the 
foundation of that great division of the geological scale with which we 
are engaged. The Carboniferous or Mountain limestone, the oldest group 
of strata for our consideration, might be hastily passed over, but for its 
presenting in this northern district a transitional type between Scotland 
and the south of England, no less important in its commercial aspect than 
iuterestmg to the geologist, in the various inquiries which it suggests. 
Turn to the Mendips, to Wales, or to Derbyshire, and we find the car- 
boniferous limestone constituted almost exclusively of actual limestone- 
strata, amounting to from 300 or 400 to above 1500 feet in thickness, and 
never exhibiting other than the smallest traces of beds of coal. But in 
Yorkshire a change sets in : the carboniferous action, if I may so term it, 
applies the thin end of the wedge, and small seams of coal of but little 
value are intercalated amongst the beds of limestone, and associated with a 
large proportion of shale and sandstone stratified with a remarkable regu- 
larity. Advancing northward, these seams increase in number and im- 
portance through the great moorland region which culminates in Cross 
Fell, the same strata rising from far beneath our feet as we stand here on 
the Lower Tyue, emerge to the daylight and compose the substance of 
the Pennine chain, which, with its lofty and heather-purpled undulations, 
forms the broad dividing ridge of Northern England. In the region of 
Weardale and Aldstone, where, in the becks and burns and in the great 
escarpment which towers above the valley of Eden, excellent exposures of 
the strata invite our study, the shales are often very similar to those of 
the coal-measures, though containing but few vegetable remains ; the sand- 
stones and grey beds frequently exhibit stems and fragments of plants 
familiar to us in the overlying strata, and the coal-seams are croio-coal or 
anthracite, resting in a bed of indurated siliceous silt or clay. Northward, 
however, of the great fault which runs nearly parallel to, but south of, the 
Newcastle and Carlisle railway, the coal-seams become, and, as it appears, 
suddenly, bituminous, and the lower division of the limestone admits more 
numerous intercalations of shale, sandstone, and coal ; and when we 
follow it to the upper district of the Tyne and beyond the river Coquet, 
the violent folding and contortion to which the strata have been subjected 
bring into view new basins or fields of coal. The true position of these 
is far beneath our ordinary measures, and has been recognized as such in 
Scotland, where they attain a vast importance. In the Berwick district, 
which has been minutely described by Mr. Boyd, it would appear that 
about 400 fathoms of carboniferous limestone measures have been detailed 
below the Whin Sill or Basaltic bed and about 100 fathoms above it, in- 
cluding in all twelve seams of coal of from 2 to 4 feet each. Certain of 
these, the Scremersten seams, appear to be remarkable in having a lime- 
stone roof. For the details of another of these basins of the hmestone 
coals, I may refer you to an excellent paper by my indefatigable friend 
Mr. Nicholas Wood, published, as is Mr. Boyd's paper, in the Transac- 
tions of the Institute of Mining Engineers. Let us pass from the upper 
beds of the limestone to the next overlying group of deposits. The Mill- 
stone Grit, or " farewell rock," as it is sometimes called by colliers, em- 
braces a series of strata unproductive in coal, and in which conglomerates 
and coarse and siliceous grits often preponderate. With this rugged 
