Vol. 51.] ' CRUSH-CONGLOMERATES ' OE THE ISLE OF MAN. 597 



EXPLANATION OF PLATES XX. & XXI. 

 Plate XX. ' Crush-conglomerate.' 



Fig. 1. [E. 2413.] Sulby G-len. 'Pebble' in slate matrix, showing diversion 

 of cleavage by it. Also, to the left of this, a hard ' pebble ' jammed 

 into the softer part of another ' pebble.' The passage of the strain- 

 slip cleavage into the gritty band is also to be seen. X 10. 



2. The same slide. The ' pebble ' in this is part of a contorted band, 



which is itself being pinched up into several isolated pieces. The 

 effect of another hard fragment to the right is also seen. X 11. 



3. The same slide. 1 This, the whole slide, shows a band of grit with bands 



of ' pebbles ' and slate on either side of it. The later strain-slip 

 cleavage makes an angle of 30° with the earlier planes of brecciation. 

 It is best seen in the slate, but traverses the grit-band and the slate 

 ' pebbles ' ; it is, however, diverted by the grit ' pebbles.' X 3 - 3. 



4. The same slide. A slate ' pebble ' traversed by strain-slip cleavage. 



This is due to a contortion which has influenced ' pebble ' and matrix 

 alike (see the ' S.W.' margin). X 11. 



5. [E. 2412.] Druidale, Sulby. The rock breaking up into phacoidal 



patches of grit and slate. Development of strain-slip, X 10. 



Plate XXI. 



Fig. 1. [E. 2414, B.] Glen Dhoo. Grit- and slate-bands outside the great 

 zone of brecciation. The distorted grit-band is breaking into frag- 

 ments, and these are again becoming disintegrated into smaller and 

 smaller patches, some of which consist of several quartz-particles, 

 others of only one. X 10. 



2. [E. 2414, A.] Another slide from the same rock-specimen. The 



separation of a ' pebble ' from the grit-band and the breaking-down of 

 it and the band into particles. X 17. 



3. The whole of the slide [E. 2414, A] to show the ragged edge of the grit- 



layer and its separation into ' pebbles.' The centre of this is enlarged 

 in fig. 2. x3'5. 



4. [E. 2411.] Druidale, Sulby. Small 'pebble' of coarse grit in ' crush- 



conglomerate.' The phacoidal outline of the quartz-grains, their 

 incipient granulation, and the ' shredding' of their ends can be seen. 

 Films of crushed slate occur between some of the quartz-grains. 

 XlO. 



5. The same, more highly magnified, and seen with polarized light. One 



quartz-grain shows undulose extinction and the beginning of the 

 granulation, which is carried a stage further at the end of the fragment. 

 The other grain is completely granulated, and in shredding off at the 

 end the granular quartz is mixed with flakes of mica. Granular 

 patches run into and even across the grains. X 17. 



Discussion. 



The President congratulated the Author, Mr. Lamplugh, who, 

 although absent, had the advantage of so able an exponent as 

 Mr. Watts. In reference to the trilobite mentioned by the Author 

 as having been obtained by Mr. Bolton, he was not aware that 

 it was derived from these altered beds, but he believed it to be 

 a true trilobite, although too imperfect for determination. 



Dr. Hicks said that he had listened with much interest to the 

 paper, as the question was one to which he had devoted considerable 



1 Mr. Lamplugh tells me that these illustrations of microscopical structures 

 might stand equally well for pictures of crags and quarries in these rocks. 



Q.J.G.S. No. 204. 2v 



