S42 



ELEVATION OF CONTINENTS A DISTINCT 



I consider it probable, that all large tracts of country or continents 

 emerged slowly from the ocean, forming at first mountainous islands, 

 before the lower countries were raised above the level of the sea. 

 The power which could upheave a continent, or, in other words, oc- 

 casion a large portion of the crust of the globe to swell out, must be 

 very different from the force which acted along certain lines, and 

 elevated mountain ranges. This power may be dependent on a 

 more general law of subterranean motion, with which we are at 

 present unacquainted ; for I deem it would be the extreme of pre- 

 sumptuous absurdity to maintain, that the causes we observe in pres- 

 ent operation, comprise the whole agencies of the material Universe. 

 The discoveries of electric and voltaic energy, and several laws of 

 crystalline and magnetic polarity, have been made only during the 

 life-time of some of the present generation ; shall we then presume 

 to fix limits to the discoveries of other powers and properties of Na- 

 ture, of whose existence we cannot at present form the most remote 

 conjectures? We might offer many instances in our own island, in 

 which the forces that have broken and lifted up the strata along cer- 

 tain lines, appear to be very different from that which elevated con- 

 tinents or large islands. The elevating force that broke and tilted up 

 the chalk strata, and the tertiary strata, along a line extending east 

 and west through the Isle of Wight into Dorsetshire, does not ap- 

 pear to have produced any considerable change on each side of the 

 line. 



In passing from Alum Bay, where the chalk strata are nearly ver- 

 tical, to the south side of the island, it is truly extraordinary to ob- 

 serve, how little the lower beds beneath the chalk, and adjacent to 

 it, appear to have been disturbed. The force which uptilted the 

 strata is altogether distinct from that mighty upheaving force, which 

 raised the whole chalk hills in the south of England from the ocean, 

 without disturbing the relative position of the strata. 



The same conclusions may be formed respecting the Wealden 

 beds (see Chap. XIII.) ; but in this case the strata have been up- 

 heaved and submerged more than once, without any great change in 

 their relative position. The repeated upheaving and submergence 

 of the secondary strata is proved by the occurrence of fresh water 

 strata, or of strata containing freshwater shells and land plants, rest- 

 ing on marine strata, and also covered with a great thickness of ma- 

 rine formations. (See Chap. VIII.) The strata in the great coal 

 formation, were deposited in the freshwater lakes or marshes of an 

 ancient country. The coal is composed of vegetable matter, and 

 sometimes contains cortical impressions of plants. The beds of 

 sandstone and shale that accompany coal, contain trunks and stems 

 of large terrestrial plants, sometimes standing in the position in which 

 they grew. In the greater number of coal fields not a vestige of any 

 marine shells is found, though they frequently contain freshwater 

 shells. In the lower part of some coal formations, indeed, there are 



