Reviews — Radiolarians, etc., in Pre- Cambrian Rocks. 417 



the side of the old Wealden Hill-range or mountain, which once 

 rose about 3000 feet above where Orowborough and other hills in 

 Sussex now are. Man existed at the time of these gravels, and used 

 the flints for tools. These gravels and the implements left in them 

 were removed by natural agencies, such as rain, rivers, sea, frost, 

 and ice, and distributed by torrential streams on the Chalk slopes 

 (now part of the North Downs) at a lower level on the flanks of 

 the range. 



These rude old flint implements have an ochreous colouring, due 

 to ferruginous gravel, whence they came; and are now found on the 

 plateau, sometimes with limited patches of some of the ochreous 

 flint gravel, together with Tertiary pebbles, less-worn flints, and 

 fragments of Lower Greensand, on the red " clay-with-flints " 

 covering the Chalk. It is shown how desirable systematic excava- 

 tions, to prove the extent and thickness of the implementiferous 

 soil, would be. 



Prof. Prestwich's history of the origin of the ancient Wealden 

 Dome, Island, and Hill-ranges, and of the gradual destruction of 

 those uplands, in the course of untold ages, with the resulting 

 formation and removal of successive geological groups of strata, 

 such as the Thanet Sands, Woolwich and Eeading Beds, London 

 Clay, Lenham Beds, and the old ferruginous gravel with its rude 

 implements above mentioned, are noticed in detail. 



The Diestian or Lenham Beds were found in the Early Pliocene 

 period ; and the denudation of Holmesdale probably began directly 

 afterwards, at about the time of the Bed or the Chillesford Crag in 

 Late Pliocene, or in post-Pliocene times ; and the old ferruginous 

 gravel had not only been formed, but washed away to a lower level 

 before that time. 



The ultimate denudation of the valley cutting ofi" the Chalk from 

 the Weald being subsequent to the formation and removal of that 

 gravel, the latter must have been pre- Glacial in age. 



I^ E "V" I IB "VT" S. 



I. — (1) Les preuves de l'Existence d'Oeganismes dans le 

 Terrain Pre-Cambrien, premiere note sue les Radiolaires 

 Pre-Cambriens. Par M. L. Cayeux. Bulletin de la Societe Geolo- 

 gique de France, 3® s., tome xxii. pp. 197-228, pi. xi,, annee 1894:. 



(2) SUR LA PRESENCE DE RESTES DE F0RA.MINIFERES DANS LES 



Terrains Pre-Cambriens de Bretagne. Note de M. L. Cayeux, 

 presentee par M. Fouque. Comptes Rendus de I'Academie des 

 Sciences. Tome cxviii. No. 25 (18 Juin, 1894), pj?. 1433-1435. 



(1) Proofs of the existence of Radiolarians in Pre-Cambrian rocks. By M. L. Cayeux. 



(2) Remains of Foraminifera in the Pre-Cambrian of Brittany. By M. L. Cayeux. 



ABOUT two years since Dr. Charles Barrois announced, in a 

 brief note to the " Comptes Rendus," the discovery of Radiolaria 

 in Pre-Cambrian rocks of the horizon of the mineral schists and 

 phyllites of St. L6, in the north of Brittany. The further description 



DECADE IV. — VOL. I. — NO. IX. 27 



