46 Notices respecting New Books. 



natural consequence of this convergence of layers of stone,) and 

 it becomes a valley with a rivulet ; both the valley and the rivulet 

 enlarge by the accession of other coombs and rivulets, the effects of 

 the branches of one greater river fissure ; and the eye of the observer 

 may, from any considerable eminence, embrace the courses of these 

 valleys, as they converge towards some of the river outlets*." 



The theory is satisfactorily illustrated from the phenomena ob- 

 servable in the valley of the river Arun, and in the vale of Green- 

 hurst. A few pages of concluding observations present some acute 

 criticism on the reasoning of the French naturalists on the sera of 

 the formation of chalk-basins, &c. : and here occurs a remark on the 

 geological site of the Thames Tunnel, which, as this analysis has oc- 

 cupied more space than was originally intended, we shall offer a 

 reply to in our next Number. 



The last section of the memoir, " On Outliers-by-protrusion," we 

 give entire; and also, as a summary of the facts relating to the geo- 

 logical structure of the weald, we copy Mr. Martin's Synoptical 

 Table. — Our opinion of the merits of the work is sufficiently evinced 

 by our remarks in the commencement of this article, and the full 

 account we have given of its contents, without the necessity of ex- 

 patiating further on the subject. 



" On Outliers by Protrusion. — In reviewing the outskirts of the 

 district made the object of the ' Survey ' of the foregoing Essay, 

 the writer's notice was drawn to a remarkable chalk-eminence 

 upon the coast, between Worthing and Little Hampton, called 

 High-Doxvn. 



" High-Down stands considerably in advance of the general line 

 of chalk-hills, and is insulated by a breadth, between them, of two 

 miles of plastic clay, covered by the woods of Patching, Clapham, 

 and Castle-Goring. It has, therefore, the character of an outlier ; 

 and upon a closer inspection, was found to present an escarpment 

 to the sea, from which it is about two miles distant, and to have a 

 northerly dip, — in opposition to the general inclination of the South 

 Downs. The observation of this phenomenon immediately sug- 

 gested the thought, that the well-known outlier of Ports-Down, in 

 Hampshire, would be found to be in the same predicament. And 

 as there is nothing to be observed of High-Down, which will not 

 apply to the larger outlier above-mentioned, a description of the 

 latter will suffice f . 



" Ports-Down is a long narrow ridge of chalk, running east and 

 west, which, rising three or four hundred feet above the level of the 

 sea, overlooks the Island of Portsea, and the several islets and in- 



* " It will not be supposed that the author means that this should apply 

 to the courses of all rivers, and in all their parts. He is now talking of the 

 Arun and the Adur, and not of the greater rivers of the globe. But the 

 principle is capable of extension to the tributary streams of these also ; and 

 all perennial rivers must have their sources in disruption, — for disruption 

 and displacement are the essence of springs and fountains." 



f " The reader may take the Ordnance Survey, or any other good map 

 which marks the high grounds, for a guide." 



lets 



