A PROBLEM FOR CHESHIRE GEOLOGISTS. 47 
intermediate ones. Hence we are driven to the conclusion that 
what is true of the Lias and other deep-water Clays of the 
Jurassic period is @ fortiori true of the Chalk. All these forma- 
tions had originally a much wider extension over the British 
Islands than they exhibit at the present day. 
Let us recall to our minds the singular accidents by which 
alone these patches of Secondary strata have been preserved 
for our study. In some cases, as in Morvern and Sutherland, 
the strata have been dislocated by faults with a throw of 
certainly not less than 2,000 feet and the softer Jurassic rocks are 
found wedged in between the harder crystalline masses. In 
other cases, as in Antrim and Skye, they have been buried under 
2,000 feet of lavas poured from neighbouring volcanoes. In 
others again, as at Linksfield and Aberdeen, they have been 
transported on-ice-rafts and buried in glacial deposits. Bearing 
all these facts in mind it seems quite impossible to resist the 
conclusion that the Secondary strata once spread over far wider 
areas than those in which they are now found, for wherever the 
necessary conditions for their preservation exist, there the 
patches of Secondary strata occur. 
If we remember the depth of water in which the Jurassic 
clays and the Chalk strata were probably deposited, and the 
thickness which they attain, it will be difficult to resist the 
conviction that almost the whole of the British Islands were at 
one time covered by deposits of Secondary age. 
It may seem a startling conclusion that at the commencement 
of the Tertiary epoch a large portion of the British Islands was 
buried under thick strata of Liassic and Oolitic age, and still 
more surprising that at the same period a great winding-sheet of 
Chalk strata varying in thickness from a few hundreds to two 
thousand feet, enveloped the whole, or nearly the whole, of our 
country, but from this conclusion I can see no escape. 
What then has become of these vast masses of rock? The 
answer is a simple one—they have been removed by denudation. 
That anything like this amount of denudation can have taken 
place since the commencement of the Tertiary period some may 
find it hard to believe. A very little consideration, however, 
will convince us that we, in this country, are apt to greatly 
underrate the importance and duration of the several periods 
of the Tertiary epoch. 
It happens that in this country the Eocene and Oligocene 
strata are comparatively thin and modern-looking deposits, the 
Miocene is non-existent and the Pliocene insignificant. But in 
other areas we find startling proofs of the enormous intervals of 
time represented by these several systems of strata. 
Every foot of sediment deposited implies the destruction of 
so much old rock. Now, as shown by Lyell, a very great 
portion of the continent of Europe has been submerged at one 
