Vol.51.] CRUSH-CONGLOMERATES OF THE ISLE OF MAN. 579 



not for the definite pronouncement of palaeontologists to the con- 

 trary, I should have been inclined to doubt its organic origin, 

 and to consider it the cleavage-marked cast of a lenticle of grit. 

 The presence of an isolated fossil in a rock of this character might 

 perhaps be explained by supposing that it was separated out from 

 its matrix during the breaking-up of the bedding, and preserved its 

 existence throughout as an independent ' pebble.' ' But the occur- 

 rence is rendered the more curious by the fact that the closest 

 search has hitherto failed to reveal similar fossils in the unbroken 

 strata. 



The Skiddaw rocks emerge rather suddenly in the cliff about 300 

 yards east of the termination of the Ballastowell ridge, and there 

 consist of crumpled blue argillaceous slates. There is a narrow 

 strip of the crush-conglomerate, 20 to 30 feet wide, in the little 

 headland 150 yards farther east, apparently let down between two 

 strike-faults ; but, as mentioned above, the main mass is cut off 

 from the coast-section by the drift-terrace. 



In summing up the evidence thus presented, I have full con- 

 fidence in stating that the breaking-up and re-arrangement of once- 

 continuous strata on a large scale by earth-movements is proved 

 beyond doubt. But the general stratigraphical relations of the 

 crushed material are less clearly established ; and in attempting to 

 deal further with this part of the subject I can, at the most, hope 

 to make a preliminary essay with the evidence in hand, in the 

 expectation that future work will supply the requisite proof or 

 correction. 



V. The Stratigraphical Relations of the Crush-Conglomerates. 



In the above descriptions attention has frequently been called to 

 the proximity to the brecciated zones on the one side of contorted 

 gritty beds, and on the other of more purely argillaceous slates. 

 These conditions, though not quite universal, are so common as to 

 constitute an important factor in the consideration of the structure. 

 In fact I have come to look upon the junction of such masses of 

 different lithological character as essential to the formation of the 

 crush-conglomerate, and where in a few instances I have not been 

 able in the field to detect this relationship, I have considered that 

 the inability was probably due to the obscurity of the sections, or to 

 later faulting or other complications. In any case, a question of the 

 utmost importance has been whether the grits and slates flanking 

 the breccias represent the same horizon throughout, or whether 

 they, in the different exposures, represent the individually distinct 

 members of a variable succession. Unfortunately the evidence at 

 present available is not convincing either way ; though I may state 



1 [That there is nothing improbable in this supposition is abundantly proved 

 by the statement of Mr. McHenry, in the discussion on this paper, that fossil- 

 if'erous pebbles do occur in a crush-conglomerate in Ireland. See p. 598. — 

 Aug. 4th, 1895.] 



