On the Chalk and Drift in Moen and Rfojen. 1(!1 



been generally described as a lava ; but Sir A. Geikie, in his 

 ' Ancient Volcanoes of Great Britain,' suggested the possibility 

 that it might be a sill. In the present paper the author endeavours 

 to prove that the rock is really a sill. The compact dolerite rests 

 directly on marmorized Carboniferous Limestone in part of the 

 quarry ; elsewhere it is separated from it by vesicular ' toadstone ' 

 or by a bed of clay which is indurated and rendered columnar for a 

 considerable depth. Above the dolerite comes another vesicular 

 • toadstone,' Thus the dolerite does not always rest on rocks 

 of the same horizon ; while the amount of alteration effected by 

 it is far greater than is usually associated with lava-flows. Taking 

 one bed in the limestone as a datum, the author establishes 

 the following conclusions: — The dolerite does not cut across the 

 beds of limestone ; the clay varies in thickness, and is some- 

 times absent ; the clay is rendered columnar and the limestone 

 marmorized to a considerable depth, unless vesicular ' toadstone ' of 

 sufficient thickness intervenes, when the 'toadstone' itself is 

 indurated ; the base of the compact dolerite is approximately 

 parallel to that of the metamorphosed rock. The dolerite itself 

 is ophitic at its centre, granular above and below, and fine-grained 

 at its margin ; it is different in microscopic aspect from the vesicular 

 ' toadstone.' Descriptions of the limestone and marble, the lavas., 

 tuffs, and clay arc also given, and the positions of the faults 

 bounding the iulier are defined. 



March 22nd.— W. Whitaker, B.A., F.R.S., President, in the Chair. 

 The following communications were read : — 

 1. ' Relations of the Chalk and Drift in Moen and lliigen.' Bv 

 Prof. T. G. Bouncy, D.Sc, LL.D., F.B.S., F.G.S., and the Rev. Edwin 

 Hill, M.A., i'.G.S. 



These two islands are separated in a north-westerly to south- 

 easterly direction by about 6b miles of sea. They both exhibit at 

 many spots the Chalk and Drift, in relations which are peculiar 

 and abnormal. Some geologists maintain that the Glacial beds 

 have been included in the Chalk by a series of acute folds ; 

 others that they have been dropped down by a series of faults : 

 others, again, explain the relationship as the result of ice- 

 action. Simple faulting appears to be insufficient, while it is a 

 circumstance not easily explained by earth-movement or ice-action 

 that the axes of the folds in the Chalk strike roughly east-north-east 

 to west-south-west in Moen, and north and south in Biigen. 



The authors then describe a series of sections in Moen which 

 lead them to the following conclusions : — 



(a) The Chalk dominates greatly over the Clay, the latter being 



often merely a local phenomenon. 

 (6) The Chalk is stained brown, and the Clay streaked with chalk 



for a few inches from the junction. 

 {<■) The Clay is often a mere facing to the Chalk, or occupies 

 semi-cylindrical or wedge-shaped cavities, which sometimes 

 seem to terminate above sea-level. 

 (d) The Clay seems often associated with superficial ravines, 

 which are probably never much prolonged below the sea- 

 level. The Chalk is strongly folded, but rarely, if ever 

 Phil. Mag. S. 5. Vol. 48. No. 290. July 1899. M 



