40 J. Clifton Ward — Modern Vulcankity. 



Upper Silurian beds were deposited upon them. • Can any one con- 

 ceive of such a denudation as is here implied being effected during 

 a more or less speedy movement ? A sweep of waters during some 

 rapid action could not have effected the truncation of many thousands 

 of feet of contorted strata, as Mr. Mallet will probably allow. But 

 given such an action as is now going on around our coasts, and given 

 long periods during which denudation could take effect upon land 

 being slowly upraised, and then as slowly depressed, such an amount 

 of work done between the deposition of the Lower and Upper Silu- 

 rian strata can be realized. Or to take another example. In Cumber- 

 land, conglomerates assigned to the Upper Old Eecl, or perhaps with 

 more truth to the base of the Carboniferous, lie unconformably upon 

 Upper Silurian beds, upon the Cumbrian Volcanic Series, and upon 

 the Skiddaw Slate. At the close of the Upper Silurian period, the 

 Skiddaw Slate of the Lake-district was probably buried beneath at 

 least 12,000 ft. of volcanic rocks and some 14,000 ft. 1 of Upper 

 Silurian strata ; yet between the period of deposition of the upper- 

 most of the Kendal Silurians and the formation of the Conglome- 

 rate of Mell Fell, there must have been a removal by denudation of 

 this 26,000 ft. of rock, to say nothing of any thickness of Skiddaw 

 Slate which may have been swept away also. I believe that this 

 denudation took place during the first upheaval of the present Lake- 

 district group of mountains, and it is hard to conceive of any pro- 

 cess by which it could have been effected other than the slow but 

 sure gnawing and planing action of the sea upon the slowly rising 

 tract, and the action of atmospheric powers upon those parts fairly 

 above the sea-level. Such a denudation, carried on by such means, 

 gives a forcible idea of the length of the Old Eed Sandstone period, 

 and there exists somewhere a thickness or an extent of strata formed 

 during that period, strictly correlative with the amount of denudation 

 produced. If we are to believe that the denudation of a great thick- 

 ness of rock could be effected during a rapid rate of elevation, we 

 must also believe that a great thickness or extent of strata could be 

 as rapidly deposited. But we know from fossil evidence that sedi- 

 mentary deposition has been in most, if not in all cases, exceedingly 

 slow ; therefore the denudation must have been proportionately so. 



With regard to the existing mountain-chains, evidence is not far 

 to seek, showing that in the main their formation dates from recent 

 geological periods. If all such giant chains as the Alps or the 

 Himalayas could be proved to be of early Palaeozoic origin, and such 

 diminutive mountain groups as those of Wales and Cumberland to 

 be of recent origin, then indeed one might be inclined to argue that 

 forces which raised the former had well-nigh spent their power, and 

 were now only equal to producing slow elevations of 2000 or 3000 

 feet. But when oftentimes the very reverse of this is found to be 

 the case, when the mountain groups of Cambria and of Cumbria are 

 representatives of some of the earliest tracts of land, when the rocks 

 forming the bulk of the Alps and the Himalayas were being formed 



1 Thickness of Upper Silurian in the Kendal district, according to Mr. AYeline. 



