342 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



the steep face of the eastern side of the mountain, and rolled down 

 on the other side. The granite blocks appear quite distinct from 

 any Irish granite, and in no respect differ from the insular kind 

 wherever that is seen in situ^. 



3. Drift Gravel. — It would seem that a deposit of this kind has at 

 one time been extensively distributed, but has suifered greatly during 

 the partial upheavals of the whole island, and the constant beating 

 of the sea into the insular valleys. It is generally found capping the 

 lower hills, and sometimes spreading out in extended platforms, as 

 in the parishes of Andreas and Jurby, and in the Vale of St. John's. 

 This deposit exhibits all the appearances of an ordinary sea-beach, 

 consisting of beds of pebbles, shingle, gravel and sand irregularly 

 stratified, and it contains (in addition to the insular rocks) chalk 

 flints. These are not uncommon even in the south of the island, 

 and have been found in digging the foundations of houses in the 

 higher part of Castletown. The sifted gravel is the great material 

 for road-making in the northern parishes, and is found reaching to 

 a height of more than sixty feet above the present high-water mark. 

 It caps the old red sandstone and the boulder formation at Peel, and 

 occurs on the western side of the Calf of Man. I consider it to be 

 a drift from the north-west f? and deposited when the level of the 

 land was from sixty to eighty feet lower than at present. Its oc- 

 currence in the Castletown basin is easily accounted for by remem- 

 bering that a channel would then exist from Port-le-Murray to Port 

 Erin ; and in the same way, by the central valley from Douglas to 

 Peel, we may account for the patch of this gravel near the Douglas 

 Light-house and in the upper part of the town of Douglas. 



The denudations of this drift during the subsequent upheaval of 

 the island are extremely interesting. The extensive swamp of the 

 Curragh, in the north of the island, seems to repose in a hollow 

 scooped out in it, so that in proceeding northward from the Cur- 

 ragh you ascend at once upon the platform of gravel and sand, 

 which appears to form a kind of fringe, like the banks of some 

 large inland lake. The same is the case in the Vale of St. John's, 

 where the turf bogs lie in hollows formed in a similar way. But 

 the most remarkable appearances are in the southern basin of 

 the island, and give the impression that the great denuding action 

 has come from the south-west by south, or up the Irish Channel, as 

 this is the direction of the long valleys which run down to the sea 

 and form the river-courses. Doubtless this form has been aided by 

 the circumstance that the strike of the undulations of the subjacent 

 limestone runs in general in this same direction ; and it is highly 



* I believe there is no point north or north-west of Barrule at which the gra- 

 nite is developed, as I have crossed SlieuhalUn (the most likely point for its de- 

 velopment) and inquired for it in vain amongst the miners in that neighbourhood. 



The existence of granite in this district would indeed relieve us fiom a con- 

 sideraljle difficulty, as we can hardly otherwise understand the pha^nomena pre- 

 sented in the distribution of the boulders. 



t There is however no necessity for supposing any other currents than those 

 at present existing in the Irish Sea, and the materials of this drift gravel aie evi- 

 deutly derived in great part from the boulder formation. 



