Vol. 55-] AND TQJi'FS NEAE CONWAY. 171 



crossed nicols, this is barely if at all apparent, being obliterated by 

 the mosaic formed by the coarse grains of the felsitic matter. 

 Pseudomorphs of cryptocrystalline matter after felspars, white 

 opaque particles which appear to be kaolin and limonite, with a few 

 small specks of unaltered pyrites, may also be seen in this section. 



No. <? is a pale pinkish to yellowish-grey nodular f el site. 

 Only one specimen was collected, containing a single nodule about 

 1^ inch in diameter and of a plano-convex form, somewhat re- 

 sembling the head of a mushroom. A section was made through 

 the centre of this nodule in a vertical direction, but in the process 

 of grinding the nodule became separated from the surrounding 

 felsite. The latter is characterized by an extremely beautiful 

 damascened fluxion-structure, the bands being corrugated and pro- 

 ducing a mottle like that on a gun-barrel or a Damascus blade. 

 It contains granular patches of a pink or white opaque substance, 

 about the nature of which I do not venture to speculate. The 

 nodule is solid throughout, and possesses an irregular, undulating, 

 banded fluxion-structure : the bands, although, in places, more or 

 less folded, passing in a comparatively straight, general direction 

 through the nodule, and exhibiting far less plication than the 

 banding in the surrounding rock. From this the nodule difl*ers in 

 translucency, a circumstance which seems to be mainly due to an 

 impregnation of chlorite in extremely small scales. ISfumerous clear 

 spots, mostly oval or circular, occur in the section of this nodule. 

 In most cases they consist of small aggregates of crystal-grains 

 with, usually, scales of chlorite, and afford no satisfactory inter- 

 ference-figures ; but in one or two instances they show a positive 

 uniaxial figure in convergent light, and are probably quartz. A 

 hazily-defined, nearly semicircular band can be seen in the section 

 on viewing it with the naked eye against the light, but this, 

 under the microscope, shows no definite boundaries and merely seems 

 to differ from other parts of the nodule in containing less chlorite. 

 A few minute cracks, now sealed, either traverse the nodule or pene- 

 trate for short distances from its surface. Being a solid nodule, 

 it seems to have originated by contraction on cooling, but whether 

 the segregation of matter now represented by chlorite had anything 

 to do with the formation of the crack which separated this nodule 

 from the surrounding lava is a question which I am unable to 

 answer. There appears to be no distinct evidence of the divergent 

 fibrous structure which so frequently characterizes spherulites. 

 Prof. Bonney has already described lithophyses both from Conway 

 Mountain and from Diganwy. Some of the nodules described by 

 the same author as occurring above the Conway Falls Inn are 

 stated by him to be ' solid to the core,' ^ as in this example. There 

 seems no evidence that the small clear patches in this nodule are 

 or ever were vesicles. The rock is a devitrified obsidian. 



No. 4- is a rather dark, purplish-grey rock. This is seen under 

 the microscope to be a felsite, with barely perceptible fluxion- 



1 Op. cit pp. 293, 294. 



