Geological Society. 



traversed by enormous and complicated faults, will hereafter be 

 comprehended at a single glance ; and the country will be visited 

 as classic ground, where the most perfect types of newer secondary 

 groups may be studied under every variety of position and com- 

 bination. Without attempting to follow the authors in their de- 

 scription of twelve of these successive groups, I may be permitted 

 to remind you of the extraordinary bed between the Purbeck and Port- 

 land formations (first noticed by Mr. Webster), containing silicified 

 trunks of coniferous trees and stems of cycadeoideae. From this 

 paper, we learn, that these trunks lie partly sunk in black earth, 

 like fallen trees in a peat-bog, and partly imbedded in the incum- 

 bent limestone j and that many of the stumps remain erect, with 

 their roots in the black soil, and their upper portions in the lime- 

 stone : and from these facts the authors conclude that the surface 

 of the Portland rock was once dry land and that on it grew .a 

 forest containing plants of a tropical form that this forest was 

 submerged under the waters of an estuary or a lake, but with a 

 movement so gentle, that neither the plants nor the soil were swept 

 away that upon this ancient forest were accumulated the mixed 

 formations of the Wealds, not much less than 1000 feet in thickness 

 and lastly, that the whole region was again sunk under the waters of 

 a deep ocean, in which were deposited the great formations of green- 

 sand and chalk. Continuing in the same spirit of induction, we might 

 add that these marine deposits again became dry land, upon which 

 lived great tribes of palaeotherian animals, now become extinct- 

 that during this period were formed the lacustrine rocks of Hamp- 

 shire and of the Isle of Wight that it was succeeded by a sudden 

 and violent convulsion, heaving on their edges the great deposits of 

 the Isles of Wight and Purbeck, and at the same time producing the 

 anticlinal axis and great longitudinal fractures, so well described in 

 this memoir. 



There can be no doubt that the same cause which upset the Isle of 

 Wight, also produced the great breaks and fissures of the Weymouth 

 district ; and that this upheaving force (for such we must consider 

 it) came into action at a recent geological period, is proved by 

 the vertically of the lower lacustrine beds at the east end of the Isle 

 of Wight. Whether this period was contemporaneous with the last 

 elevation of the Eastern Alps may well admit of doubt : to substan- 

 tiate a fact like this, many links are yet wanting in the chain of evi- 

 dence; and England has, if I mistake not, been acted upon by far too 

 many local disturbing forces, to be ever brought rigidly within the 

 systems of the great European chains considered in the researches 

 of M. Elie de Beaumont. 



The investigation of the faults and dislocations interrupting the 

 continuity of our secondary deposits is becoming, daily, a sub- 

 ject of increasing importance ; and we are now called upon, not 

 to regard them as solitary phaenomena, but to trace them through 

 whole regions, and to examine their relations to each other. These 

 N.S. Vol. 9. No, 52. April 1831. 2 P great 



