588 MR. W. W. WATTS ON THE [Nov. 1 895, 



(iv) The formation of the crush-conglomerate has occupied one 

 stage only in a series of earth-movements which had 

 previously folded the rocks and afterwards impressed a 

 shear-cleavage upon them. 



(v) There is reason to believe that the crush-conglomerate 

 marks a definite stratigraphical horizon ; and that it was 

 originally dispersed in a rude zone which afterwards 

 suffered contortion. 



Plate XIX. 



Sketch-map of the Isle of Man, on the scale of 4 miles to the inch, showing 

 the outcrop and strike of the crush-conglomerates. 



APPENDIX. — Petrographical Notes on the ' Crush-Conglo- 

 merates ' of the Isle of Man. By W. W. Watts, Esq., M.A., 

 E.G.S. 



[Plates XX. & XXI.] 



As most of the rocks collected in the Isle of Man by Mr. Lam- 

 plugh have passed through my hands, it has fallen to my lot to 

 describe the specimens of ' crush-conglomerate ' for him. At his 

 request I add to his paper a few notes on the macroscopic and 

 microscopic characters of selected examples of these specimens. 

 The microscopic observations appear to confirm, in all essential 

 points, the deductions drawn by him from the field-evidence. They 

 even enable us to go a little further on some points : — to trace the 

 disintegration of the grit-bands ; to watch the process of ' pebble '- 

 making on a small scale ; to see the breaking-up of the ' pebbles ' 

 themselves into miniature ' crush-conglomerates ' ; to follow the 

 erosion of the ' pebbles ' into single grit-particles involved in slate ; 

 and, finally, to state the amount of secondary change which the 

 rocks have undergone. 



It will be convenient to divide these notes under the following 

 heads : — 



(1) Sedimentary rocks outside the great area of movement 



and crush. 



(2) The ' crush-conglomerates ' : (a) as a whole ; (6) their con- 



tained fragments. 



(3) The dj'kes penetrating the conglomerate. 



(4) Metamorphism of the 'crush-conglomerate.' 



(1) The Sedimentary Rocks. 



It is very rare to find in the Skiddaw Series of the island any 

 sedimentary rocks, except those of very coarse grain, which have 

 not been crushed and sheared by earth-movements. Outside the 

 principal zone of crush and brecciation the rocks still possess their 

 original clastic structure, but they begin to show, by much deforma- 



