590 ME. W. W. WATTS ON THE [Nov. 1895., 



islands in the slate. Where this occurs the straits of slate are 

 highly puckered and often have a fine strain-slip cleavage developed 

 in them, which does not, however, penetrate into the grit. These 

 divisional planes vary in direction in different parts of the slide and 

 appear to he here merely a local phenomenon, due to the pinching 

 of the slate in the jaws of the grit. They bear no relation to the 

 incipient separation of the grit-promontories into islands, which 

 must be attributed to another and an earlier movement. 



The dividing of the grit-band into fragments can almost be watched 

 in the two slides cut from this specimen. The disjecta membra vary 

 in size, from fairly large patches to those which contain only a few 

 grit-particles, and even these are beginning to go to pieces, so that 

 one is compelled to believe that many of the separate grit-particles 

 in the slate, which are evident strangers there, have been floated 

 off from the grit-band, and are the ultimate term of the disinte- 

 gration. The illustration shows admirably the size of these frag- 

 ments and their gradual disintegration down to actual single grit- 

 particles. (PI. XXI. figs. 1, 2, & 3.) 



[E. 2415.] — This specimen shows alternate bands of grit and 

 slate on its cut surface, and the microscopic slide gives an excellent 

 example of the ' cleavage-foliation ' of Sorby. The strain-slip 

 cleavage runs at right angles to the stripe, and the cleavage-planes- 

 are planes of foliation marked by a deposit of pale brown mica. 

 Where the quartz-grains are large enough to be well seen they have 

 a phacoidal shape, but in the coarser bands the quartz is in com- 

 plex grains arranged parallel to the foliation. There is a diversion 

 of the cleavage-planes in traversing the grit-bands. The rock is a 

 mica- schist. 



[E. 2416.] — The stripe of this specimen is a plane which has been 

 minutely puckered and in the slide it is seen to be crossed, at an 

 angle of about 60°, by a strain-slip cleavage in the slate-bands. In 

 places the grit is torn off and forms lenticles in the slate. Pale 

 brown mica is developed along the planes of stripe, in the slate- 

 bands, and it runs into the strain-slip planes in wavy surfaces. 

 The amount of mica present here is very great, but there is much 

 less in the grit-bands. A few colourless needles which I take to 

 be felspar occur in the slate, and a few needles of tourmaline are 

 also present. A great quantity of ilmenite, in fine, needle-like 

 crystals, occurs scattered quite irregularly all over the slide ; it has 

 no definite orientation. The shredding-out of the coarse beds is 

 observable, but the fragments remain along the line of stripe. 



One or two other specimens which have been examined show 

 knotted structure and the development of garnet, mica, and ilmenite. 

 In one case at least this alteration appears not to be connected 

 with any igneous mass, for the rocks are all well exposed in two* 

 valleys, one on either side of the col on which the specimen was 

 collected. 



