G, H. Kinahan — Re-arranged Glacial Drift. 169 



of whicli the cliffs were composed. These varieties of the re-arranged 

 drift dovetail or graduate into one another, but most of the mud is 

 deposited far out, or in deep still places, while the sand and gravel 

 accumulate nearer in shore, or in places where there are currents, 

 and the Glacialoid drift is characteristic of the shore deposits. The 

 last is principally formed after heavy weather, where the cliffs have 

 been undermined or shaken, so that landslips take place. In heavy 

 weather these materials due to landslips will be carried out much 

 further than ordinary, forming widespread thin sheets, while at 

 other times they will be more compact. Sections of such recent accu- 

 mulations can seldom be examined, but on rare occasions they are 

 exposed during extensive excavations for docks and other sea works. 

 It can easily be understood, as the sea only denudes the drift forming its 

 margin to a certain depth, that underneath these recent marine deposits 

 there may be a continuous mass of undisturbed Boulder-clay drift 

 (unless it is displaced by Post-Glacial faults) ; while the Glacialoid 

 drift may join into the glacial drift, but although it may be very 

 similar in aspect, is in reality unconnected with it, and a member of 

 the more recent marine drift, the blocks and fragments that give 

 it its supposed glacial character having been derived nearly un- 

 changed from the Boulder-clay drift. It should also be mentioned 

 that in many of the deposits of Glacialoid drift accumulating in these 

 estuaries and bays, most of the blocks and fragments of stone, as in 

 some river gravels, are arranged more or less on edge.^ 



What is now happening in places on the west coast of Ireland 

 seems to be nearly similar to that which in former ages took place 



1 This pitching or being on edge of the blocks and fragments of the " re-arranged 

 glacial drift" I have observed in the drift in different places ; but in none do they ap- 

 pear to be so conspicuous as in the co. Wexford, where they are characteristic of the 

 Glacialoid drift, some of these drift sections being a mile or more in length. In accumu- 

 lations forming at the present day I have observed blocks or fragments on edge in the 

 following : at the bends of rivers, especially in mountain streams ; in masses of drift due 

 to landslips, where the mass has slipped outwards, and not gone down perpendicularly ; 

 and in the in-shore accumulations in estuaries, where the drift between the base of 

 the cliff and low water-mark may have all or most of the contained blocks and frag- 

 ments on edge. I can also imagine shore-ice or an iceberg pushing along on a mass 

 of drift would shove up the blocks and fragments. Mr. A. Wyley, late geologist to 

 the Government of the Cape of Good Hope, thus writes on the subject : — "A solid 

 body, such as a landslip or a moving iceberg, would, I fancy, lift stones off the flat, and 

 set them on edge; the horizontal thrust in either case overcoming the force of 

 gravity and acting at right angles to the same. In other words, as, under the action 

 of gravity, flat stones arrange themselves at right angles to the force, so, in case of a 

 force acting at right angles to the force of gravity, it is natural that the flat stones 

 should change their position in the same degree; but as the force of gravity would 

 still be acting, their position would in most cases be determined by a ' component ' 

 of the two forces. This explanation will only apply to where the mass of mud has 

 been moved by some strong horizontal force, and may also account for the fact of the 

 more or less upright position of slates and such like stones at river bends, where there 

 is always a strong horizontal force in the eddy." In the co. "Wexford the upright 

 position of the stones may in part be due to shore-ice or stranded icebergs ; but it 

 seems more probable that the drift was similarly formed to the shore accumulations 

 of some estuaries of the present day, as all these drifts are adjoining what must have 

 been land when the shelly drifts were being deposited, the great lengths of the 

 sections being due to the present cliffs running with very similar, if not nearly 

 identical, bearing to the cliffs that bounded the Fre-drift islands. 



