338 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



form a concretionary mass on the lee side of any obstruction, (as^ 

 for instance, of a pebble bedded in the sand,) the action of the water 

 forming elongated cavities or pipes in other portions. In the in- 

 stance occurring in the south of the island, not only is this seen 

 with respect to the pleistocene sands, but a raised beach of more 

 modern date, resting on a partially denuded bed of the boulder clay, 

 has acquired a similar consolidation and concretionary structure ; 

 and still further, a quantity of moss growing on the cliff' is now 

 being gradually converted into travertine. If this explanation should 

 be accepted for the phasnomena occurring in the north of the island, 

 it will remove any difficulty which might arise from considering the 

 concretionary structure as necessarily coincident in time with the 

 pleistocene deposit. 



In the central valley of the island running from Douglas to Peel, 

 and also in the Baldwin valley, it appears difficult to determine what 

 portion of the water-moved mass belongs to the boulder clay forma- 

 tion. There is no exposure in the sea-cliffs and in the interior, but the 

 superficial gravel and alluvium conceal everything*, and in the south 

 of the island we have evidence of its existence through the whole 

 of the limestone basin. All along the coast it appears as a loamy 

 clay resting immediately on the older rocks, and occasionally we find 

 thicker patches of it containing, in the greatest abundance, scratched 

 fragments of the limestones, &c. of this basin, with a few rounded 

 pebbles of the foreign rocks before mentioned. The mass of it form- 

 ing Hango Hill, at the head of Castletown Bay, exhibited in the 

 annexed sketch, and presenting a cliff" to the south twenty-four feet in 



The cliff at Hango Hill, near Castletown. 



1 



4. Modern raised beach of gravel and shingle, with bones of mammalia. 

 3. Ancient raised beach consisting of fine sand stratified. 

 2. Drift gravel. 



1 . Boulder clay with angular scratched boulders of limestone and some roxmded pebbles of 

 foreign rocks. 



height, aff'ords an excelleiit study of the general arrangement, though 

 the clay at the base is mostly covered up by the sands of the present 

 sea-beach. The blocks of limestone (some weighing upwards of a ton), 

 almost angular, with parallel scratchings on their broader faces, lie 

 piled one over the other in the utmost disorder, like masses of ice 

 drifted down a stream after a thaw. They all have the appearance 

 of having come from Skillicore, near Coshnahawin, a mile and a half 

 to the north-eastward, where the beds, having been altered by heat 

 and traversed by deep intersecting cracks, break up naturally into 

 rhomboidal blocks, which are largely used for building purposes. 



But the best evidence of the direction in which the drifting cur- 

 rent has most powerfully acted is seen near the Stack of Scarlet, on 



* Two road cuttings made in the spring of the present year (1846), the one at 

 Douglas and tlie other at Peel^ exhibit the stratified drift gravel resting upon 

 masses of the boulder formation from twenty to thirty feet tluek. 



