1847.] CUMMING ON THE GEOLOGY OF THE CALF OF MAN. 183 



There are red and grey syenites, porphyries, granites, grits and sand- 

 stone, either from Cumberland or the south of Scotland. And though 

 there is no doubt that the drifting currents of this period passed over 

 the limestone area of the south of the island in this direction, the 

 author has not met with a single pebble of the limestone in this mass 

 of boulders and gravel. A good section is developed in consequence 

 of a large excavation having been made into the hillock for the pur- 

 pose of procuring gravel for the neighbouring road. 



It will be observed that the stratification or quasi-stratification is 

 not horizontal ; it seems in fact to follow in general the outline of 

 the surface of the hillock itself, and to consist of concentric layers 

 forming a semi-ellipsoidal mass. 



As before noticed, it is situated on an elevated ridge of the schist 

 — not exactly on the summit, but rather to the western side ; on the 

 eastern side, in the direction over which the materials constituting 

 this hillock must have passed, is a deep depression*, in which is a 

 turf bog, whence a small rill takes its rise. The depression is such 

 that a person standing there has no view of the sea in any direction, 

 yet the author could discover in this hollow no traces whatever of 

 gravel, boulders, or sand, nor in any other similarly situated hollows 

 on the island. The gravel beds on the low ground at the eastern 

 and western extremities of the island f belong to raised beaches of a 

 more recent geological period. At the highest point of the island, 

 near the western pile, he found one or two small boulders of granite, 

 and on the Mull Hills J, at a corresponding height, large boulders of 

 syenite and porphyry, where also we have the appearance of a ter- 

 race (rather inclining towards the sea) of gravel and loamy sand, 

 but not exhibiting any clear evidence of regular stratification. 



With respect to the origin of the gravel boss on the elevated 

 eastern extremity of the Calf, the author cannot conceive it attribu- 

 table to any violent diluvial action, as the rushing of great waves of 

 translation over the surface of the island, though he has no doubt of 

 the fact of such diluvial action at some period or periods. Any 

 such waves must rather have exercised a denuding force upon so 

 elevated and moveable a mass, and are inconsistent with the occur- 

 rence of the large bed of fine sand in the lower portion, as vt^ell as 

 with the absence of any like deposit in any of the neighbouring 

 hollows. 



The absence of any such deposits seems also to militate against 

 the idea that this boss is to be regarded as a relic of a larger extent 

 of sand, gravel and boulders spread out on the then sea-bottom. It 

 appears perfectly isolated, and at unity only with itself. The only 

 remaining hypothesis, (as it seems to the author,) and the one which 

 he ventures to propose for the solution of the problem, is that of a 

 grounded iceberg, melting and depositing quietly its load, subjected 

 however to the gentle action of the drifting current from the E.N.E. 

 {i. e. nearly magnetic east), of which the evidence was detailed in 



* See Section 3. f See Map of Island. 



X See Section 1, and Map of the Calf Islet. 



