390 Prof. Sedgwick on the New Red Sandstone Series in the 



neighbouring country. I have already noticed the accumulations of old allu- 

 vial detritus south of Eden ; but they bear no comparison to the vast heaps of 

 similar materials which cover, to an unknown depth, nearly all the tracts of low 

 land bordering on the coast of Cumberland : and all the islands off the coast of 

 Low Furness are exclusively composed of rounded masses of rock (sometimes 

 many tons in weight,) brought down from the old Cumbrian and Lancashire 

 chains, and imbedded in a kind of red alluvial loam derived from the degra- 

 dation of the red sandstone *. In some parts of the coast the alluvial con- 

 glomerates are solidified, and only to be distinguished from the true conglo- 

 merates of the new red sandstone by the greater freshness of the imbedded 

 pebbles : for the pebbles of the old conglomerates (however distinguishable 

 in mineral structure,) have, in the regions I am describing, almost universally 

 undergone a progress towards decay, and are sometimes hollow and entirely 

 incoherent f. 



Before I go on to the next section of this paper, it may be well briefly to 

 recapitulate. 



(1.) The red sandstone series above described appears among the last ra- 

 mifications of the Eden, in a position decidedly unconformable to the carbo- 

 niferous limestone;};. 



(2.) In its prolongation it rests upon the upper portion of the carboniferous 



* The erratic blocks of the Cumbrian mountains are not confined to the places above indicated, 

 but have been carried, in incredible abundance, over the plains of South Lancashire and Cheshire. 

 They are also found, at a great elevation (for example, near the top of the pass from Macclesfield 

 to Buxton), on the chain of hills which separates Cheshire and Derbyshire. I also found them 

 last summer, though generally much diminished in size, on the flanks of the Denbighshire hills, 

 above Oswestry. To what cause are we to attribute this drift of the Cumbrian rocks ? Wliatever 

 it niay have been, it must have acted at a comparatively recent period ; for many of the travelled 

 bowlders, though lying bare on the surface, are very little decomposed, and still ring under the 

 hammer. The present condition of the Cumbrian valleys confirms the previous statement ; for an 

 examination of them leads us inevitably to two conclusions : 1st, that they were not formed by the 

 erosion of the waters now flowing through them ; 2ndly, that the causes by which they were brought 

 into their present form must have ceased their action at a comparatively recent period. Every Cum- 

 brian valley which contains a lake gives an independent proof of what is here asserted. 



t Considered as mere mineral specimens, the conglomerates of the old red sandstone, in the 

 North of England, have often a much newer appearance than those of the new red sandstone. This 

 fact may be partly due to the cementing principle, and partly to the more indestructible nature of 

 the imbedded pebbles of the old red conglomerates. Both in the South-west and North of England, 

 the fragments of mountain limestone, which enter so largely into the new red conglomerates, are 

 generally well preserved where the cementing principle is highly calcareous; but where the cement 

 is siliceous, the limestone pebbles are, I believe, universally decomposing, and in some instances 

 have almost disappeared. 



+ Plate XXV. fig. 2. 



