COAL MEASURES BENEATH ESSEX.
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plain of the Middle Danube to the east with the Mediterranean
Basin to the south of the main axes of Alpine elevation, then feebly
outlined. The range and extent of these areas of deposition con-
tinued pretty much the same during the Cretaceous period, during
which the Chalk formation of our southern hills, which underlies
the Tertiary strata of this part of England, was built up. Then
followed further movements, which upon the whole were move-
ments of elevation for North-Western Europe, giving us the much
more contracted basins, in which the older Tertiary strata (the
Eocene) were deposited. Of such strata examples are seen in the
sands and clays of the Rye-street brickyards, and in the London
clay (the estuarine equivalent of the great Nummulitic Limestone
marine formation), which (with its capping of later Boulder-clay)
forms the upper portions of nearly all the higher country in this
part of England, where the chalk does not come to the surface. In
this Eocene period it was that such minor axes of elevation as that
of the Weald were developed, though these, doubtless, in most cases
were but the further accentuation of such minor folds of the older
strata as had been covered up by the secondary or Mesozoic strata.
It is with such minor axes of elevation of the older rocks that we are
chiefly concerned in estimating the probability of the existence of pro-
ductive Coal measures under Essex.
If now we turn our attention to the coal measures in which coal
is worked in Britain and in Europe, we find them so distributed as
to bear just such a relation to the older Palaeozoic strata as we should
expect, from what has been already discussed. Thus we find the
great coal measures series of the Scottish Lowlands lying in a great,
broad, synclinal trough, the general axis of which (complicated by
minor flexures) trends north-east and south-west, between the older
strata which rise into the Southern Uplands on one side and the
Highlands on the other. The great coal fields of Durham and
Northumberland and of Yorks and Notts (on the one side) and
that of Lancashire (on the other side) flank the great Penine axis
of elevation. The Midland Counties coalfields, which by later
crust movements have been thrown into the separate basins of
Staffordshire, Leicestershire, Warwickshire, and Worcestershire, may
be connected in a series with those of Gloucestershire and South
Wales by the coal measures which have been proved in recent years
by borings at Burford (Oxfordshire) and Clandon (near Bath), the
whole series representing a broad belt of deposition in the Carboni-
L