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At first sight, hardly any rock could seem to present so un 

 promising a field for investigation as the Penrith Sandstone does. 

 The rock itself is almost entirely devoid of traces of fossils ; and it 

 is so remarkably uniform in general character that from top to 

 bottom there is hardly a single bed in it that can be separately 

 traced more than a few yards. Then, again, the planes of stratifi- 

 cation generally found in most sedimentary rocks are replaced 

 here by what are called planes of false-bedding, which afford us no 

 trustworthy information as to the amount of inclination the rock 

 has undergone, and therefore present us with no data for determining 

 the true thickness of the rock. Altogether, it is a most unsatis- 

 factory rock for the geological surveyor to have to deal with. 



In attempting, therefore, to work out the physical geography of 

 this part of England at the time the Penrith Sandstone was being 

 accumulated, we often have to go far afield for evidence, and to 

 pursue lines of inquiry different from what are generally taken in 

 the study of the other rocks. First of all we have to make out its 

 relations to the older strata. I have before taken occasion to 

 point out that this rock lies indifferently upon the edges of widely- 

 separated members of the older strata, and that it may be found 

 reposing upon the upturned edges of the newest Carboniferous rocks 

 of Edenside, as well as upon the contorted Silurian strata of the 

 Lake District. This means that a vast interval of time had elapsed 

 between the completion of the Carboniferous Series and the advent 

 of the Penrith Sandstone. The older rocks had been consolidated, 

 let down many thousands of feet nearer the centre of the earth, 

 and consequently squeezed into folds to adapt themselves to the 

 smaller space, afterward they were again upheaved, broken up into 

 great wedges by faults, and then were worn away by denudation, 

 until the upturned edges of the rocks were shorn off to one general 

 level, so that in the end a vertical thickness of nearly twenty 

 thousand feet of strata had been removed. The time required to 

 accomplish this result must have been vast beyond conception. 

 More than this, sufficient time had elapsed for the almost complete 

 replacement of the teeming life of the Carboniferous Period by a 

 group of animals of a character decidedly different in many respects. 



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