Vol. 56.] EARTH-MOVEMENT IN THE ISLE OF MAN. 23 



research. I agree with him on the main point — that there is con- 

 clusive evidence of considerable earth-movement since the deposition 

 of the Carboniferous volcanic rocks at the southern end of the Isle of 

 Man. He seems to me to have established this point beyond dispute. 

 How far the tumultuous structures in some of the agglomerates 

 should be attributed to the original volcanic conditions of accu- 

 mulation, and how far to subsequent earth-movements, is a question 

 on which there is room for difference of opinion. Possibly some of 

 those structures which Mr. Lamplugh would regard as subsequent 

 are among those which seem to me more probably original. We 

 can hardly exaggerate the confusion of arrangement in the materials 

 of many volcanic agglomerates. And when these materials come 

 subsequently under the operation of movements of the terrestrial 

 crust, it is obvious that the task of separating the one set of effects 

 from the other becomes exceedingly difficult.' 



Prof. C. Lapwoeth expressed his admiration of the clear and 

 convincing way in which the Author had laid his most interesting 

 results before the Society. It was most instructive to note how 

 phenomena once regarded as depositional and of unquestionably 

 contemporaneous origin, had shown themselves to be dynamic and of 

 subsequent date. Although the Author and others still adhered to 

 the view that the volcanic phenomena were of Carboniferous Lime- 

 stone age, he felt himself that, as interpreted by the fold-theory of 

 deformation, there was much to be said in favour of the view that 

 they also were of subsequent date and of the age of tbe crust- 

 movement. In great crust-movements tbe differential deformation 

 and friction of the stratified masses moving on opposite sides of a 

 plane of contrary movement gave origin to mechanical breccias, and 

 caused the rolling-out of masses and fragments into ball- like forms. 

 Igneous matter, making its way between the moving masses, may 

 consolidate as sills where the pressure is great, and as amygdaloidal 

 masses where the pressure is locally relieved. The presence of 

 associated superheated waters, etc. would account for the dissolution 

 of limestones, the formation of cherts, with included derivative 

 fossils, and even for the simulation of natural bedding. As move- 

 ment progressed intermittently, we should have tbe formation of 

 subterranean agglomerates, tuffs, and breccias, which would be 

 forced locally sometimes between bedding-planes, sometimes into 

 dyke-like fissures. Where, finally, the impounded waters, gase?, 

 igneous matter, and mixed materials found an exit to the surface, a 

 vent of escape for some of them would be formed. If vertical, it 

 would be an ordinary pipe-vent or neck ; if oblique, it might be 

 mapped as a sheet of agglomerate, or a row of volcanic necks. 



As respects the relationships of these Isle-of-Man structures to 

 the Pennine knoll-reefs described by Mr. Marr, he had himself 

 little or no doubt that both were primarily of dynamic origin. The 

 axes of the great crust-folds recognizable in Britain and Western 

 Europe were four in number — two primary (parallel to the lines of 

 latitude and longitude), and two resultant (diagonal to these) ; while 

 the ' swirl' or direction of the overcreepwas left-handed, answerirg 



