10 o\ THE ORIGIN OF MOUNTAINS. 



In Cretaceous times, as Prof. Duncan remarks, " evidently the 

 greater part of Europe, North Africa, Arahia, Hindostan, and much of 

 northern and eastern Asia, Australia, South America, and large tracts 

 of North America were under water. But cretaceous land-surfaces, 

 the edges of the deep sea, may be traced in Queensland, the Eastern 

 Himalayas, Central Europe, and in the north-western States of 

 America.'' 



Indeed the present distribution of tbe land-masses was mainly 

 sketched out in Tertiary times. 



Our Welsh and Lake Mountains were, bowever, true mountains 

 long before that period. They were depressed in the Chalk Sea, and 

 perhaps only isolated peaks appeared above tbe surface of the waters, 

 just as, no doubt, there are now old land-surfaces beneath the ocean, 

 indicated by certain oceanic islands. 



Again and again have our mountains been submerged, even, 

 perhaps, as late as Glacial times, for on Moel Tryfaen, near Caernar- 

 von, at a height of over 1,300ft., recent marine shells have been found 

 that may indicate submergence to that extent. But, with all these 

 fluctuations, tbe mountains have continued much as they were before, 

 and we have no right to say that their upheaval is of Glacial or Post- 

 glacial date, because we have vestiges of such comparatively recent 

 deposits on their sides. Their form and structure bespeak their 

 antiquity. 



We know too little at present to write a connected history of the 

 formation of the great mountain systems. Nor can we do more than 

 remark upon this connection between the outlines of the great 

 continents. When, however, we look at a diagram showing the 

 relation of the highest mountain (29,000ft.) to the deep ocean, (we 

 don't know its greatest depth yet,) how trivial seem the ups and downs 

 of twenty or thirty thousand feet. 



Mr. Grove compares mountains to "the heads of the nails which 

 fasten the lead to the dome of St. Paul's." We are seldom able to 

 realise the entire height of the mountains. The valley of the 

 Chamouni is 3,500ft. in height; and those who ascend Snowdon 

 usually commence at some distance above the sea-level. 



Then, agaiu, as Mr. Grove remarks, "few mountains rise at a 

 Btedper angle than 45°, and most are much less." This means an 

 elevation of one in one. The Peak of Teneriffe, which, from the 

 harbour, seems to be almost over your head, is said to slope only at an 

 angle of 12°, or about one in five. The slope is, no doubt, intimately 

 connected with the stratification or structure of the rocks, and is thus 

 but the unglo of repose. 



(To be continued.) 



Up. cit., i>. 19. 



