button to main menu   Otley's Guide 1823 (8th edn 1849)


This version of the essay on geology is from Jonathan Otley's Descriptive Guide to the English Lakes, 1823, 8th edn 1849. The copy used is in the Armitt Library, item AMATL:A1180.
It is amended from the essay in the 1st edn 1823, to accomodate advances in geological understanding.
I am grateful to Tim Pettigrew for his comments on the essay.

The Latest Geology

Jonathan Otley recognised the broad tripartite nature of the rocks in The Lakes, each characterised by a distinct topography.
The earliest rocks consist of slates of a soft character giving rise to the more rounded fells of Skiddaw and Grassmoor in the north west of the area. These Skiddaw Slates are now known to be of early Ordovician age.
The second group he described form the craggy volcanic peaks of the central area of The Lakes. These Borrowdale Volcanic rocks are now interpretted as the remnants of a volcanic chain erupting partly underwater and partly into the open air. Later than the Skiddaw Slates, these rocks are also believed to be of the early Ordovician age.
The third group includes the Coniston Limestone, late Ordovician, and the Brathay Flags which Jonathan Otley correctly, in the 8th edn 1849, interprets as belonging to the early Silurian age. The Silurian system had been described by Adam Sedgwick; he had talked with Jonathan Otley who was able to incorporate the ideas in his notes.
The 1849 essay predates the recognition of the Ordovician period, which was defined by Charles Lapworth, 1879. This introduction to geological theory resolved a dispute between Adam Sedgwick and Roderick Murchison, who were allocating the same beds of rocks in north Wales to the Cambrian and Silurian respectiveley. Charles Lapworth recognised that the fossils in the disputed beds were different from those in either the Cambrian or Silurian, and should be in an intermediate period of their own.
Jonathan Otley describes various igneous rocks, Skiddaw Granite etc, which were thought to lie beneath and be older than the rocks above and around them. These are now known to have been intruded, in a molten or part molten state, into the overlying rocks which already existed.
A new theory of glacial erratics is mentioned, but Jonathan Otley still has his doubts about glaciers, and prefers to ascribe the position of the erratics to the action of water. The coming of railways is noticed in remarks on the transport of slates from quarries to the coast.

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Page 144:-
WHEN this essay was first published, in 1820, the structure of the mountainous district of Cumberland, Westmorland, and Lancashire, was but little understood; scientific travellers had contented themselves with procuring specimens of the different rocks, without taking time to become acquainted with their relative position. Since that time, the subject has received more attention from persons conversant with geological inquiries; especially from the distinguished Professor Sedgwick, who in 1824 and following years, subjected this district to his untiring examination. In his address to the Geological Society, Feb. 18th, 1831, the Rev. Professor deigned to compliment the author, as being the first to point out that 'the greater part of the central region of the Lake Mountains is occupied by three distinct groups of stratified rock of a slaty texture.'
On a cursory glance at the lake mountains, they present little of that regularity in appearance which is usually observed in a stratified country; yet, on a nearer inspection, the stratification may in many places be distinctly made out; and the following remarks are offered to the notice of such as require only a general outline
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