TRANSACTIONS OF SECTION C. 711 



view of the Untergrund or sub-oruatal region as the layer that induces superficial 

 flow by dragging the solidified crust upon its surface. Carrying the question into 

 still more speculative regions, he asked if the cause of epochs of mountain-building 

 on the earth as a whole might not be due to some primordial periodic change of 

 temperature in the interior, inherited from the time when OUV pUnet formed part 

 of what we call a variable star. 



The following Reports and Papers were then read :^ 



1, Third Report on the Crystalline Rocks of Anglesey. 

 See Reports, p. 283. 



2. On the Finding of Silurian Beds in Kent. By W. Whitaker, F.R.S. 



A boring has lately been made, to a great depth, at Messrs. Curtis & Harvey's 

 works, on the Thames Marshes at Cliffe, for the purpose of getting a supply of 

 water, firstly from the Chalk and then from the Lower Greensand. It has failed 

 in this, the wafer from both formations being too salt to be of any use ; but it has 

 succeeded in adding a geologic formation to the Kentish list, and that the oldest 

 yet found in the county. 



Details of the section will be given in a forthcoming Geological Survey Memoir 

 on the Water-supply of Kent. It should be noted that the division between some 

 of the formations is doubtful, but any error from this cause is imwateria.! in tha 

 following abstract :-^ 



Alluvium and Eiver Gravel . 77 ^ 



Upper, Middle, and Lower Chalk 656 (or more) 



Gault 208 (or less) 



Lower Greensand ... 96 (or less) 



Dark grey clayey rock . . 37 (or more) 



1074 feet. 



Nearly the whole of the Chalk has been pierced, the topmost part only being 

 absent. The thickness given to the Gault is a little more than in the borings at 

 Chatham, Friudsbury, and Strood eastward, and still more than at Erith (Cross- 

 ness) westward. The thickness given to the Lower Greensand is also more than 

 at Chatham, whilst at Erith there is none of this formation. 



The chief interest of the boring, however, lies in the facts that the floor of the 

 older rocks, which has been proved in many places in Kent, was reached at a level 

 of about 1,030 feet below Ordnance Datum, and that the Palseozoie foruuation 

 found is of Silurian age, nothing older than Devonian having been hitherto 

 recorded from the deep borings of the county, and that only at Brabourne, unless 

 the red rocks at Crossness should turn out to be of like age. 



The proof of the Silurian age of the lowest beds is given by the occurrence of 

 fossils at the depth of 1,063 feet, Atrypa reticularis a,nd Plectambonites ha,vmg 

 been determined at the Palseontological Department of the Geological Survey 

 by Mr. H. A. Allen, from samples of the cores sent by Mr. Baldwin Latham. 

 There are traces of other fossils. 



The practical value of the boring is that it puts a northern limit to the Kent 

 coal-field in its neighbourhood. 



3. On a Case of Thrust and Crush Brecciation in the Magnesian Lime- 

 stone, Co. Durham, By David Woolacott, D.Sc, F.O.S. 



Along the two miles of cliff between South Shields and Marsden the breccias 

 that form so marked a peculiarity of the Magnesian Limestone of north-east 

 England are best exposed. The rocks seen are the Yellow Sands, Marl Slate, and 

 Mftgnesian Limestone, but tjie ^exposure pf the first two are too small for the 



