594 MR. W. W. WATTS ON THE [Nov. 1 89 5, 



to discriminate between them. A careful study of the illustrations 

 will give a clear idea of the general relations of these two primary 

 constituents of the ' crush- conglomerates.' 



[E. 2412.] — A dark slaty rock or phyllite containing fragments 

 of pale grit. The rock splits into slabs, which are at an angle of 

 about 30° to the minutely puckered foliation ; these slabs are 

 defined by the ' shear-cleavage.' The elongation of the fragments 

 is in the plane of foliation. Owing to the less-marked character of 

 the second movement, this specimen is very valuable as showing 

 the origin of the conglomeratic structure. Three slides have been 

 prepared : two are in the plane of intersection of the strain-slip 

 with the contorted foliation, and almost at right angles to the elon- 

 gation of the fragments ; they consequently show only the strike 

 of the divisional planes, which appear as cleavage-cracks. The 

 slide has a damascened appearance, owing to the direction in which 

 the mica-folia are cut, and the matrix of the rock is rich in sericite 

 which is clearly a secondary product. The fragments do not show 

 any decisive orientation in these slides, nor do they seem to be in 

 any way related to the foliation-planes. 



The other slide [E. 2412 C], however, is cut at right angles to 

 the cleavage and foliation, and parallel to the elongation of the 

 fragments, so that it is very instructive. The phyllitic matrix is 

 rich in sericite, aud is well foliated. The folia are in wavy bands, 

 with the development here and there of strain-slip cleavage-planes 

 which traverse matrix, or fragments, or both, according to the 

 nature of the material of which they are made ; such planes define 

 the slabby surfaces of the hand-specimen. The grit- and slate- 

 fragments are all phacoidal in outline, and are drawn out along the 

 foliation-planes, folded, torn, and enwrapped by the folia of the 

 matrix. Fragments are occasionally but rarely cut off abruptly, 

 and even when this is the case with one end, the other is frequently 

 drawn out into the matrix. The nature of the fragments and the 

 absence of any extraneous types of rocks must be relied on here to 

 prove that the brecciation has occurred in situ. The whole rock 

 has undergone more mineral change than the specimen [E. 2413] 

 described. 



(5) ' Pebbles ' in the Conglomerate. — The following specimens are 

 described : — 



[E. 2409.]— Narradale Stream, W. 5° S. of 838 level on road, 

 Sulby. Fragment measuring 14 feet across. 



[E. 2410.] — Sulby Glen under Close. Grit-inclusion in con- 

 glomerate. 



[E. 2411.] — Sixty yards north of Druidale Junction, Sulby 

 River. 



[E. 2419.]— Crag in Sulby Glen, south-east of Killabraggah. 



[E. 2421.] — Road-cutting in Narradale, south of stream, 

 Sulby. 



[E. 2409.] — This is the largest fragment hitherto found in 

 the conglomerate ; it is 14 feet in diameter, and its outer face is 

 smoothed and striated. Within the surface-layer the rock has not 



