568 Correspondence — Mr. G. H. Kinahan. 



outliers, the steps by which the isolation and removal of these 

 patches to a distance was accomplished remain to be traced ; and 

 here, perhaps, without undue exercise of imagination where 

 evidence is wanting, it may be suggested that after inversion the 

 adjacent face of the Mendips might have assumed the form of a 

 high escarpment made up of the softer Coal-measures capped by the 

 overthrown limestones, when land slippage, during the wasting 

 backwards of the escarpment, might have taken place, allowing 

 large masses of the harder rocks above to subside ; or a succession 

 of landslips might each be accompanied by an outward as well as a 

 downward movement. 



In support of this suggestion, I may mention an escarpment some 

 1500 to 2000 feet in height, with which I am acquainted, composed 

 of various soft and more consistent beds below, capped by unusually 

 hard and massive ones above. Along this scarp land-slippage has 

 taken place to such a degree that great detached masses of the upper 

 sections have settled down on the sloping outcrop of the softer beds, 

 until they have, in several instances, arrived by combined processes 

 of slipping and weathering back at distances from their main outcrop 

 quite comparable with those of the outliers in question from the 

 suggested escarpment of inverted beds. Some of these detached 

 masses exceed the dimensions of the Upper Vobster outlier ; and, so 

 far as can be judged without having seen the locality, there appears 

 to be no insuperable difficulty in accounting for the position of these 

 outliers in this way. 



It should be noticed in connexion with the subject of such great 

 inversions, that disruption or faulting may have accompanied the 

 distortion of the anticlinal arches, permitting the inverted strata to 

 fall away, or else the whole set of beds, including both the limestones 

 and those above them, must be supposed to have turned back upon 

 themselves again, as shown in the figure at E. No instance, upon a 

 large scale, in which this is proved to have occurred, has fallen within 

 my experience, though some sections have suggested it, and in the 

 absence of such recurvature, displacement amounting to faulting 

 may, after all, have been a necessity in some part of the process by 

 which these features were produced. 



Tl «f. ^. 



On the Nomenclature of Bocks. 

 Please correct the following in the Geological Magazine for 

 September : — 



Page 426, line 22, in two places, trachyte for trachalite. 



G. H. Kinahan. 

 BOULDER-CLAY IN IRELAND. 



Sir, — I can assure Mr. Birds that it is perfectly incorrect to suppose 

 that an Upper Boulder-clay in Ireland resting on " middle sands and 

 gravels " has been proved in any place. Normal Boulder-clay has been 

 found in many places resting on sands and gravels, but the latter 

 cases are of an age prior to the accumulation of the Glacial Drift 



