RECENTLY EXPOSED NEAR BEAUMARIS. 471 



abouts appears to be about E., or even a little IS", of E., but it bends 

 back again to the S.E. The last schist exposed is of a greenish 

 colour and rather compact structure, with some epidote and quartz- 

 veins, which dips roughly 20° E.S.E.* Here we are on the higher 

 ground, a little west of Gallows Point, overlooking the strip of flat 

 land already mentioned. These schists are cut by two or three basalt 

 . dykes f. 



I have had slides cut from the principal varieties of the schist for mi- 

 croscopic examination. The purplish schist (about 150 yards from the 

 entrance to the drive) consists of quartz, a flaky green mineral, and 

 an iron-oxide (probably haematite) associated with a little manganese. 

 The quartz is in irregular granules of chalcedonic aspect, I believe 

 developed in situ. The other two minerals are to some extent scat- 

 tered over the slide, but are also associated in wavy bands. In part 

 the former may be a chlorite ; but I am disposed to regard most of 

 it as a hydrous mica akin to biotite. I have examined these mine- 

 rals with considerable care, but cannot say that I feel much confi- 

 dence in determinations of the optical characters of these small 

 crystallites, as there are so many obvious sources of error. In the 

 compact chloritic rock, near the entrance-gate, there is more of the 

 green mineral, some of which more closely resembles a chlorite, and 

 less quartz and ferrite ; calcite also occurs in a vein. The highest 

 schist exposed in the drive has a general resemblance to the first 



* An interesting section is exposed in a pit near a house called, I believe, 

 Pen-y-Parc, a short mile from the cemetery-gate. Here is a compact greenish- 

 white quartzite overlain by a dull greenish-grey schist. The upper surface of 

 the former is rather uneven ; but I incline to consider this the result of a bend- 

 ing of the beds, and not to indicate an unconformity. The former consists of 

 quartz-grains of variable size, subangular to rounded, the larger being the most 

 rounded, imbedded in a minutely granular quartzose matrix, the whole being 

 occasionally cracked and recemented by very minutely crystalline quartz, in 

 which are occasional flakes of a pale greenish micaceous mineral. The quartz- 

 grains are generally crowded with small cavities, in very many of which are 

 minute moving bubbles, occasional small prisms of a pale green mineral, and 

 fine " hairs " like rutile. The schist is less altered than one would expect ; it 

 consists of small subangular grains of quartz in a matrix of quartz and the usual 

 filmy green mineral, with an occasional larger flake of pale mica. The whole 

 has evidently been much compressed. Some twenty feet or so of the quartzite 

 are exposed, and a little lower down the hill schists resembling those already 

 described crop out. Maeroscopically one would correlate these beds with the 

 other sohists ; but the dip, which is about N.N.E., does not agree very well, 

 the quartzite is not seen on the scarp below, and the retention of a fragmental 

 condition , probably original, in the upper schist is a good reason for hesitating. 

 The quartzite has a considerable resemblance to that on Holyhead Mountain, 

 though in the latter bubbles seem to be much less frequent. Both, however, 

 may very well have obtained their materials from such rocks as the granitoid 

 series near Ty Croes. 



t The last seen of these consists of a plagioelastic felspar well preserved, with 

 rather large angles (up to 30°) between the extinctions of successive lamella?. 

 In these are many colourless belonites. The augite has lost its characteristic 

 aspect, consisting of a mass of granules partly dusky, partly bright-coloured 

 with crossing nicols ; there are many scattered rods and wel -defined sharply 

 angular crystals of haematite or perhaps, in some cases, ilinenite. The minerals 

 appear to have consolidated in the inverse order to that in which they are 

 described. 



