312 PROCEEDIIirGS OF THB GEOLOGICAL SOCIETY. [Apr. 5, 



4. On the Foemation q/" CiEaiJES," and their hearing upon Theomes 

 attributing the Excavation of Alpine Valleys mainly to the 

 Action of Glacieks. By the Kev. T. G. Bonney, M,A., F.G.S. 



The following paper is an attempt to examine how far a theory 

 which during the last few years has obtained more or less support 

 from many very eminent geologists, can be applied to one of the most 

 remarkable features in several mountain-valleys. Although " cirques " 

 are more commonly associated with the Pyrenees, they are by no 

 means infrequent or on a small scale in the Alps ; and as I know 

 the former mountain-chain only at second hand, I shall confine my- 

 self to the latter, and to those instances which I have personally ex- 

 amined. 



In venturing to treat of a subject so full of difficulty, and to op- 

 pose the opinions of persons far more eminent than myself, I may 

 venture to plead as my excuse that I do not write without some ex- 

 perience of mountain-regions, seeing that I have twelve times visited 

 the Alps, have wandered, generally on foot, over almost the whole 

 chain, and have had during many of these journeys this subject of 

 mountain-sculpture especially present before my mind, so as to be 

 constantly on the watch for evidence bearing upon the various 

 theories that have been advanced. 



First let me briefly describe a few of the most remarkable cirques, 

 beginning with the Creux de Champs. 



This is an approximately semicircular amphitheatre on the northern 

 face of the Diablerets, forming the head of a short glen terminating the 

 valley of La Grande Eau, which joins the Ehone at Aigle. Vast preci- 

 pices of limestone and shale enclose it, which are crowned with short 

 wide glaciers, and surmounted by the blunt peaks of the Diablerets, 

 the highest of which reaches an elevation of 10,666 feet above the 

 sea. The floor of this glen, though encumbered with moraine stuif, 

 and intruded upon by the great taluses beneath the precipices, is 

 tolerably level, and is probably about 4000 feet above the sea*. 

 Above the slopes an almost unbroken wall of limestone rock rises 

 for at least 2000 feet ; shales, alternating with narrower bands of 

 limestone, then reduce the precipitousness and produce the ledges 

 whereon the glaciers rest ; and, finally, the limestone peaks rise like 

 broken battlements on the summit of the wall. From these snow- 

 laden ledges numerous streams gush down the rock, some mere white 

 threads of spray, others turbid cascades, whose volume varies with 

 the hour of the day and the state of the weather. Speaking in 

 general terms, we may say that for an arc of about 80° this cirque 

 is enclosed by a nearly vertical waU of precipices rising full 5000 feet 

 above its comparatively level floor. The strata exposed, though here 

 and there contorted, and in one place at least folded, lie on the whole 

 pretty evenly, and appear to dip gently a little south of west. 



The Fer-a-ChevaJ. — This cirque differs from that last described in 

 being situated just on one side of a large peak, and in opening into 



* The Hotel des Diablerets, at its mouth, is 3832 feet ; and the fall of the val- 

 ley-bed is not rapid. 



