TRANSACTIONS OF THE SECTIONS. 5? 



These masses of igneous antl sedimentary rock are traversed by numerous trap 

 dykes or veins, often accompanied (always on the north side) by mineral veins, to 

 which they serve as the under walls. The trap dykes generally dip northward. 



Channels of slate several yards wide inclosing mineral veins are also frequently 

 found ; the slate is highly laminated, and the laminse are parallel to the dip of the 

 vein. 



On the Explanation of certain Geological Plicenomena hy the Agency of 

 Glaciers. By Edmund Batten, M.A. 



The object of the author in this communication was chiefly to excite discussion 

 concerning the transport of large boulders and erratic blocks observed in different 

 parts of Europe. His account was restricted to the gigantic boulders of Switzerland 

 and the shores of the Baltic, and the erratic blocks traceable to the Grampian chain of 

 Scotland. The former have been frequently described, and are considered by the 

 Swiss geologists to have been conveyed by immense glaciers extending across the 

 great valley of Switzerland ; and near Edinburgh, appearances are observable which 

 seem to indicate something like a similar cause having acted. It is a question, how- 

 ever, whether any theory of glacier motion will account for the passage of glaciers 

 over these districts, and the improbability of a great extent of glaciers moving like a 

 river across a country was pointed out. Allusion was then made to the iceberg 

 theorj', and its greater probability as a means of transporting heavy blocks ; and the 

 author concluded by enforcing the necessity of numerous observations, with a view to 

 the solution of the problem. 



On the Occurrence of Marine Shells in tJie Gravels of Ireland. 

 By Thomas Oldham, M.R.I.A., F.G.S. 



The author commenced by noticing the prevalence of gravel and diluvial deposits 

 in Ireland, where they occur in long, low rounded ridges called Eskars, which stretch 

 for many miles in nearly a right line ; or in detached rounded hills, or forming undu- 

 lating grassy plains. These gravels have hitherto been considered not to contain any 

 organic remains, and have been carefully distinguished from some deposits of clay 

 containing marine shells which have been noticed in several places along the coasts, at 

 elevations varying from 50 to 300 feet above the present level of the sea. Mr. Oldham 

 did not consider this distinction well-founded. There were with the gravel deposits, 

 patches of clay identical, in general mineral character and in the pebbles of the trans- 

 ported blocks which they contained, with those known to contain marine shells ; and 

 similarly, with the clay deposits, were layers of gravel, consisting of the same ingre- 

 dients, and similarly arranged with the gravels of the undoubted eskars. Tracing 

 further, he had extended the range of these fossiliferous clays, finding them in very 

 many places, and in the centre of the island as well as along the coast; and at eleva- 

 tions above the present sea level of 200 to 600 feet ; in several cases also in distinct 

 eskars. Taking these facts as proof of a general alteration of level, he showed two 

 maps, on which were represented the amount of land which would be visible were this 

 alteration to have taken place to the extent of 1000 feet and 500 feet. In the former 

 case what is now Ireland would only have existed as a few small scattered islands in 

 the north and south ; and xhe same would have been, in a general view, the case, if the 

 alteration were only to the extent of 500 feet elevation or depression. 



These deposits the author referred to the aera of the Newer Pliocene or Pleistocene, from 

 the occurrence of the characteristic shell, the Nucula ohlonga (Brown) ; with this was 

 found the Astarte gairensis, and about twenty species now existing in the adjoining seas. 



Under these so-called diluvial deposits the rocks were almost in variably found polished, 

 furrowed and scratched; the edges of the projecting beds rounded off and smoothed, 

 and the whole ploughed up in parallel lines. These scratches were to be found nearly 

 at the present level of the sea, and also at very considerable elevations above it. 



On the Physical Character and Geology of Norfolk Island. 

 By Capt. Maconochie, R.N., K.H. 

 The group of which Norfolk Island is the principal is situate in lat. 29° 2' S. and 

 168° 2' east long., 900 miles E.N.E. of Sydney, and 1350 N.E. from Cape Pillar in 



