Geological Society of London. 511 



The President remarked that at a depth of 5 miles the pressure upon a rock would 

 be 120,000 lbs. to the square inch, an element which, he thought, ought to be taken 

 into consideration. 



2. " On the Physical Conditions under which the Cambrian and 

 Lower Silurian Kocks were probably deposited over the European 

 Area." By Henry Hicks, Esq., P.G.S. 



The author indicates that the base line of the Cambrian rocks is 

 seen everywhere in Europe to rest unconformably upon rocks sup- 

 posed to be of the age of the Laurentian of Canada, and that the 

 existence of these Pre-Cambrian rocks indicates that large continental 

 areas existed previous to the deposition of the Cambrian rocks. The 

 central line of the Pre-Cambrian European continent would be shown 

 by a line drawn from S.W. to N.E. along the south coast of the 

 English Channel, and continued through Holland and Denmark to 

 the Baltic. Its boundaries were mountainous ; they are indicated 

 in the north by the Pre-Cambrian ridges in Pembrokeshire, in the 

 Hebrides and Western Highlands, and by the gneissic rocks of 

 Norway, Sweden, and Lapland. The southern line commenced to 

 the south of Spain, passed along Southern Europe, and terminated 

 probably in some elevated plains in Russia. Between these chains 

 the land formed an undulating plain, sloping gradually to the S.W., 

 its boundary in this direction being probably a line drawn from Spain 

 to a point beyond the British Isles, now marked by the 100-fathom 

 line. The land here facing the Atlantic Ocean would be lowest, 

 and would be first submerged, when the slow and regular depression 

 of the Pre-Cambrian land took place. 



The author points out that the evidence furnished by the Cam- 

 brian and Lower Silurian deposits of Europe is in accordance with 

 this hypothesis. In England they attain a thickness of 25,000 — 

 30,000 feet; in Sweden not more than 1000 feet; and in Russia 

 they are still thinner, and the earlier deposits seem to be wanting. 

 In Bohemia they occupy an intermediate position as to thickness and 

 order of deposition. The author discusses the phenomena presented 

 by the Welsh deposits of Cambrian and Lower Silurian age, and 

 shows that we have first conglomerates composed of pebbles of the 

 Pre-Cambrian rocks, indicating beach conditions, then ripple-marked 

 sandstones and shallow-water accumulations, and then, after the 

 rather sudden occurrence of a greater depression, finer deposits 

 containing the earliest organisms of this region, which he believes 

 to have immigrated from the deep water of the ocean lying to the 

 S.W. After this the depression was very gradual for a long 

 period, and the deposits were generally formed in shallow water ; 

 then came a greater depression, marked by finer beds containing 

 the second fauna ; then a period of gradual subsidence, followed by 

 a more decided depression of probably 1000 feet, the deposits formed 

 in this containing the third or " Menevian " fauna. This depression 

 enabled the water to spread over the area between the south of Prussia 

 and Bohemia and Norway and Sweden, there being no evidence of 

 the presence of the first and second faunas over this area. The 

 filling up of this depression led to the deposition of the shallow- 



