200 
THE PHYSICAL GEOGRAPHY OF THE PAST. 
been accumulated and systematized, it becomes possible, by 
a comparison and correlation of results, and by the applica¬ 
tion of strict methods of reasoning, to make out the order of 
past events, and to read by the light of the present the 
physical changes which this world of ours has undergone in 
ages long past. This is, indeed, tlie highest aim of geology, 
which has been well defined as the “physical geography of 
the past,” and, I think, I shall do well by attempting to show 
you something of the methods by which this reconstruction 
of old-world features is accomplished, and by applying them 
to the elucidation of some of the past conditions of the 
portion of central England in which we live. The period 
which I have selected for this purpose is that in which were 
laid down the great mass of the Carboniferous Rocks—rocks 
including the Mountain Limestone and the Coal Measures. 
Owing to their vast superficial exposure in Great Britain 
and Ireland, and to the manner in which they have been 
explored for their mineral wealth, we have, perhaps, in the 
Carboniferous Bocks, a greater accumulation of important 
facts to work upon than we have in any other system. 
Before attempting to throw any light upon this chapter in 
the ancient physiography of our Midland district, I must, in 
the first place, call your attention to the existing conformation 
of the surface, and to the close connection there is between 
the nature of the underground rocks and the features of the 
country as now presented to us. 
If we look at any good physical map of England we notice, 
running almost down the centre of the Northern part of the 
country, a broad range of hills, which forms a great water- 
parting, from the western side of which the streams run into 
the Irish Sea, and from the eastern into the North Sea. This 
broad ridge of high ground, one of the most striking natural 
features of our country, is known as the Pennine Range, and 
has been aptly described as the backbone of England. It 
attains its highest elevation of about 2,600 feet in the North 
Riding of Yorkshire, and in the Peak, the highest part of North 
Derbyshire, it reaches about 2,000 feet above the sea level. 
When followed from the northern counties southward this 
ridge of high land is found to terminate abruptly a few miles 
to the west of Ashbourne, in the Weaver Hills, and it is this 
southern portion of the range which serves to illustrate in 
the best possible way the geological structure of the Pennine 
Chain. 
The rocks constituting the Chain belong exclusively to the 
Carboniferous System, that great division of the older rocks 
which, in its upper part, contains all the principal coal seams 
