Correspondence — Mr. J. R. Dakyni. 239 



crushings, such as bespeak ice -action, or inclose small masses of 

 Boulder-clay in their lower layers ; so that I consider it established, 

 independently of further considerations, that these gravels at all 

 events elate back to glacial times. I have other reasons for thinking 

 so, but content myself at present with the above. I would only add 

 that it by no means follows, because these gravels began to be 

 deposited before ice-action had ceased in this area, that their deposition 

 did not continue down to Post-glacial times. In other words, while 

 their lower part is of Glacial, their upper part may be of Post- 

 glacial age. 



South of the town is a corresponding cliff, consisting of current 

 bedded sand and gravel, and finely laminated sandy clays (Phillips' 

 Warp Beds). These do not show any undoubted signs of ice-action ; 

 they would seem, however, to have once been continuous with the 

 Sewerby gravels, but to have had their continuity interrupted by the 

 denudation of the valley by which the Gypsey Pace escapes to sea. 



In none of the above-mentioned beds have any shells been found 

 as yet ; this, though it proves nothing, is quite in keeping with the 

 idea of their being of Glacial age, and is possibly due to their having 

 been deposited in shallow seas freshened by the melting of the great 

 ice-sheet; the current bedding, dipping now in one direction and 

 now in the opposite, bespeaks tidal currents in shallow water, and 

 the warp-like character of the laminated clays is equally suggestive 

 of a tidal estuary. 



I may mention that I have found fragments of marine shells in 

 sand-beds in the interior in localities where they have not been 

 noticed before — viz. in the remarkable series of sand-hills running 

 south from Harpham Moor and at Brigham. These, I suspect, will 

 turn out to belong to the set of beds described by Phillips at pages 

 61 and 62 of his work on the Yorkshire Coast. 



It is right to add that the gravels at Bridlington mentioned above 

 are here and there overlaid or replaced by more recent fresh- water 

 deposits, gravels, and marls. This, of course, is well known. 



Bridlington Quay. J- K- Dakyns. 



GLACIAL TROUGHS BENEATH THE GLACIER DES BOSSONS. 

 Sir, — Glacial grooves and furrows are always described in 

 geological works as running in the direction of the ice-flow which 

 formed them. That this should, perhaps generally, be the case, is 

 so obvious that it may seem superfluous to give proofs thereof; nor 

 are such far to seek ; they are these : the direction of the grooves is 

 often found to coincide with that of glacial striae, with that of the 

 transport of erratics, and with the direction of motion indicated by 

 crag and tail, and by the forms of roclies moutonnees. Yet it is not 

 always so. In many cases grooves and furrows, such at least as are 

 broad and shallow, must have been formed by ice moving not along 

 but across the direction of the grooves. This would be apt to be 

 the case especially on steep ground, and such I would call troughs. 

 I saw a very good instance of this in the year 1873, in the case of 

 the Glacier des Bossons. From a point in the hill-side beyond the 



