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produced by great upheaving forces. Such are some of the great 

 transverse valleys of the Alps. Of valleys of denudation our island 

 offers a countless number. Some are of simple origin : for example, 

 the dry combes and valleys of the chalk, which appear to have 

 been swept out by one flood of retiring waters during some period of 

 elevation. Others are of complex origin, and are referrible to many 

 periods, and to several independent causes. Lastly, we have valleys 

 of simple erosion : such are some of the deep gorges and river chan-r 

 nels in the high regions of Auvergne, excavated solely by the long 

 continued attrition of the rivers which still flow through them. 



I should not have dwelt so long upon this subject, had it not occu- 

 pied a large portion of our attention during the past year; and I 

 may be pardoned for entering a record of my own views on a ques- 

 tion of no small complexity, and on which there is still much con- 

 trariety of opinion. 



During the past year we have been presented with several memoirs 

 describing formations superior to the chalk : which 1 shall also notice 

 in the order of the subjects, without any regard to the time when they 

 came before us. — In a Paper by Dr. Fitton on the structure of a por- 

 tion of the low countries in the north of Fiance, among other inter- 

 esting details, is a description of three of this great class of for- 

 mations. He points out deposits in the neighbourhood of Calais, 

 Antwerp, and Tongres, which resemble the Crag of Suffolk. He com- 

 pares the sands of St. Omer, Cassel, and Lille, with the sands which 

 overlie the chalk in the London basin : and he states that the arena- 

 ceous beds of the hill of Cassel (like similar beds at Brussels) con- 

 tain large suites of fossils, generally agreeing with those of the Lon- 

 don clay. Lastly, he describes in detail the structure of St. Peter's 

 Mount near Maestricht, and shows that the inferior beds form a gra- 

 dual passage into the white chalk on which they rest; while the upper 

 beds bear marks of degradation and mechanical interruption, and 

 offer no indication of a passage into the superior sands. And he 

 adds that, out of more than fifty species of organic remains collected 

 by himself from this deposit, not more than ten are found in our best 

 catalogues of chalk fossils. 



I may here remark, that the suite of fossils in the Cassel sands 

 throws no difficulty in the way of their comparison with the lower ter- 

 tiary sands and plastic clay of England, The terms London clay and 

 Plastic clay may be preserved as convenient mineralogical designa- 

 tions. They mark, however, nothing more than the subdivisions of 

 one great deposit between the lower and the higher members of 

 which there is no line of zoological separation. In the London and 

 Paris basins, there is a great chasm between the secondary and ter- 

 tiary systems to be filled up by the future labours of Geologists. The 

 Maestricht beds are so nearly related to the formation on which they 

 rest, that they may be regarded as the last term of that new series of 

 deposits which we hope hereafter to find interpolated between the 

 calcaire grossier and the chalk. 



A Paper by Mr. Murchison makes us acquainted with the structure 



