Curiosities of Science. 107 



other, and which frequently seem to have brought them from 

 a distance. There are also similar masses of pebbles found 

 at very great elevations, to which the sea appears never to 

 have been able to reach. We find them in the Alps at Valor- 

 sina, more than 6000 feet above the level of the sea ; and on 

 the mountain of Bon Homme, which is more than 1000 feet 

 higher. There are some places little elevated above the level 

 of the sea, which, like the famous plain of Crau, in Provence, 

 are entirely paved with pebbles ; while in Norway, near Qued- 

 lia, some mountains of considerable magnitude seem to be 

 completely formed of them, and in such a manner that the 

 largest pebbles occupy the summit, and their thickness and 

 size diminish as you approach the base. We may include in 

 the number of these confused and irregular heaps most of the 

 depositions of matter brought by the river or sea, and left on 

 the banks, and perhaps even those immense beds of sand which 

 cover the centre of Asia and Africa. It is this circumstance 

 which renders so uncertain the distinction, which it is never- 

 theless necessary to establish, between alluvial masses created 

 before the commencement of history, and those which we see 

 still forming under our own eyes. 



A charming monograph, entitled " Thoughts on a Pebble," 

 full of playful sentiment and graceful fancy, has been written 

 by the amiable .Dr. Mautell, the geologist. 



ELEVATION OF MOUNTAIN-CHAINS. 



Professor Ansted, in his Ancient World, thus characterises 

 this phenomenon : 



These movements, described in a few words, were doubtless going 

 on for many thousands and tens of thousands of revolutions of our 

 planet. They were accompanied also by vast but slow changes of other 

 kinds. The expansive force employed in lifting up, by mighty move- 

 ments, the northern portion of the continent of Asia, found partial vent; 

 and from partial subaqueous fissures there were poured out the tabular 

 masses of basalt occurring in Central India ; while un extensive area of 

 depi'ession in the Indian Ocean, marked by the coral islands of the 

 Laccadives, the Maldives, the great Chagos bank, and some others, were 

 in the course of depression by a counteracting movement. 



Hitherto the processes of denudation and of elevation have 

 been so far balanced as to preserve a pretty steady proportion 

 of sea and dry laud during geological ages ; but if the internal 

 temperature should be so far reduced as to be no longer ca- 

 pable of generating forces of expansion sufficient for this ele- 

 vatory action, while the denuding forces should continue to 

 act with unabated energy, the inevitable result would be, that 

 every mountain-top would be in time brought low. No earthly 

 barrier could declare to the ocean that there its proud waves 

 should be stayed. Nothing would stop its ravages till all dry 



