D. MACKINTOSH ON HIGH-LEVEL MARINE DRIFTS. 



355 



derangement is the violent stranding of an iceberg or mass of floating 

 ice from the N.W. on the previously accumulated clay, which it 

 pressed forwards and downwards until it reached the sand, which it 

 ploughed up and inverted, and then bent and shattered the edges of 

 the slaty laminae, so as to be able to roll up parcels of clay and 

 slate- chips in the sand. The line marking the commencement of 

 the slaty curvature is nearly horizontal ; but the upper termination 

 inclines slightly in the direction of the movement of the floating ice 

 (at first probably raised a little above the level of flotation by the 

 impact, and afterwards slightly lowered so as to regain its normal 

 level). This section bears no real resemblance to some which are 

 found in districts where traces of ice-action are absent, and which 

 are believed by some geologists to have been caused by ordinary 

 atmospheric action. On Moel Tryf an the finely laminated sand shows 

 no trace of having ever been disturbed by the percolation of rain- 

 water or by frost, while the preservation of the numerous shell- 

 fragments in continuous though contorted layers of sand and fine 

 gravel has evidently (as Darbishire long ago pointed out) been 

 owing to the clay preventing the downward passage of rain-water. 

 As Moel Tryfan is in the midst of a glaciated district, and as ice 

 capable of bending the slates and contorting the sand must have 

 brought the erratic stones, including chalk-flints from Ireland, why 

 have recourse to any other supposition to account for the phe- 

 nomena ? 



Fig. 1. — Laminated Sand and Bent Slates on Moel Tryfan. 



B.E. N.Wo 



A A, Slates ; B B, Sand, with parcels of slate-chips and Boulder-clay ; 

 C C, Boulder-clay. 



7. Direction of Floating Ice in Ireland. — According to the Bev„ 

 M. H. Close the principal direction of floating ice in Ireland during 

 the glacial submergence was from about to S.E. ; so that the 

 local floating ice would only have to persevere in this direction, 

 after leaving Ireland, in order to reach Moel Tryfan. 



8. Were all the Moel-Tryfan Shells brought by Floating Ice ? — 

 This idea would appear to be untenable for the following reasons : — 

 (1) The shells must at first have been somewhere in situ, and why 

 not on Moel Tryfan ? (2) The Mollusca may have lived where the 

 erratic stones were imported as well as where they were exported. 



