62 Royal Society : — 



tortious. He shows this to exist in England and in France, and 

 supports the case by quotations from various French authors. It 

 is then shown that in the valley of the Somme these phenomena 

 are most marked and decisive, — large blocks of sandstone, some 

 weighing four to five tons, and derived from tertiary strata twenty to 

 forty miles above Amiens, being found in the St. Acheul gravels, 

 and the beds being much contorted. These contortions do not depend 

 on any pressure exercised by the blocks, but result from some dis- 

 turbing power applied and removed. To illustrate this point refer- 

 ence is made to two sections in his former paper (Phil. Trans, for 

 1860, p. 299). 



The author conceives that the only adequate cause to produce many 

 of these effects is river-ice, the transporting power of which is well 

 known, whilst he quotes the observations of travellers in Northern 

 America to prove the power of such ice to pile-up the shore 

 shingle in great conical heaps. That the old pleistocene rivers were 

 also larger and more rapid than the existing rivers is evident from 

 the great quantity of debris, the prevalence of gravels, the coarseness 

 of the sands, and the general absence of mud-sediments. Another 

 agent of considerable power is referred to, viz. ground-ice, but is re- 

 served for consideration further on. 



The Fauna of the High-level Gravels. — The organic remains are 

 considered with reference especially to the climatal conditions of the 

 period ; and it is regretted that, owing to the scarcity of fossils 

 except at a few places, and to the want of specific information with 

 regard to the mammalian remains and the levels, the evidence on 

 many points is unavoidably incomplete. The best-determined group 

 is that of the Mollusca, in examining which the valuable assistance 

 of Mr. Gwyn Jeffreys is acknowledged. The author gives a Table 

 showing the group of land and freshwater shells inhabiting, in 

 England and France, the area now described, from which comes out 

 the striking result, that out of 109 living species 43 are found in 

 the deposits of the high-level gravel period. There is a scarcity 

 of Unionidse and Paludinidse, whereas Limnseidse and Helicidse are 

 very common. In many places shells are scarce or altogether want- 

 ing ; but this is common in all rivers subject to floods or bringing 

 down much shingle. All the species are of existing forms, and all, 

 with four exceptions, inhabit the same districts as formerly. Their 

 range is then reviewed, and it is shown that though a considerable 

 proportion of them are found in the South of France, a still larger 

 proportion exist in Scandinavia, and that as many as thirty-five out 

 of the forty-three species are met with in Finland, including the 

 common forms, such as Succinea putris, S. Pfeifferi, Helix hispida, 

 H.nemoralis, H. pulchella, Pupa muscorum, Limnceus pereger, L. pa- 

 lustris, L. truncatula, Planorbis corneus, P. vortex, P. marginatus, 

 P. albus, P. spirorbis, Bythinia tentaculata, Valvata piscinalis, Pisi- 

 dium amnicum, &c. From these and other facts it is concluded that, 

 while there is nothing in the Mollusca to necessitate a climate different 

 from that of the present day, there is nothing to require restriction 

 to an identical climate, while at the same time the tendency of deve- 



