Yol. 56.] EARTH-MOVEMENT IE" THE ISLE OF MAN. 13 



III. Eelation oe the Carboniferous Limestone 

 to the Volcanic Series. 



These patches of limestone among the finer ash have hitherto 

 been held to be truly interbedded, and to denote intervals of 

 quiescence in the volcano during which calcareous sediment 

 accumulated in hollows of the surface of the submarine tuff. The 

 similar patches among the basaltic rocks and coarse agglomerates at 

 Scarlet Point have been, however, generally recognized as out of 

 place, and have been usually supposed to owe their position to some 

 peculiar effect of the eruptive activity which is considered to have 

 had its focus in this quarter. 



But in all the sections alike these strips of limestone have 

 undergone disturbance of a singular type, for which no adequate 

 explanation seemed forthcoming, while a serious difficulty in 

 considering them to have accumulated in hollows of a sea-floor of 

 pumiceous ash was that in most cases they are free from ashy 

 admixture. And it is now my opinion that all the larger of these 

 lenticles, as well as most of the smaller blocks of dark argillaceous 

 limestone among the coarse agglomerate, have been torn up from 

 the underlying limestone-floor during a sliding forward or over- 

 thrusting of the volcanic series upon this floor. The only calcareous 

 deposits which I can definitely recognize as having been originally 

 interbedded with the Volcanic Series are certain thin bands of ashy 

 limestone associated with finely-laminated, and sometimes nodular, 

 calcareous tuff in the middle portion of the outcrop, between 

 Cromwell's Walk and Close-ny-Chollagh Point. These beds have 

 been implicated in the general disruption brought about by the 

 overthrusting, but are seen here and there in large patches in a 

 comparatively unbroken condition. The grounds for my conclusions 

 are contained in the following descriptions of three typical sections, 

 of which the first lies at the eastern extremity of the volcanic out- 

 crop, the second at its western extremity, and the third in the 

 midst of the series. 



IV. The Section at Scarlet Point. (Pig. 1, p. 14.) 



When the section on the eastern side of Scarlet Point, south of 

 the little gully which separates the broad undulating scars of the 

 dark flaggy Lower or Castletown Limestone from the jagged mass 

 of the volcanic rocks, was examined at the lowest tides, it was 

 found that the flaggy strata did not terminate, as previously 

 supposed, at the gully, but were prolonged beneath a confused pile 

 of massive limestone and limestone-breccia which occurs in close 

 association with the volcanic rocks on the southern side. The 

 edges of the rolling limestone-flags were truncated by a plane 

 dipping gently southward, upon which rested massive recemented 

 limestone-breccia. The dark stratified limestone was traceable as 

 a low-water reef almost up to the northern front of the great 

 basalt-pinnacle known as the Stack of Scarlet, encircling the base 

 of the high crags of vesicular basalt and coarse agglomerate which 



