140 PROF. T. m'kenny hughes on the 



The conglomerate above described, from its hard nature, generally 

 forms a ridge, and so is known to be almost always present at the base 

 of the green and purple grit and slate series. It may be followed along 

 the shore N.E. of Gored Gith, near Bangor, and can be seen at 

 intervals striking S. across the ridge E. of Eriddodd and W. of 

 Bangor Station, with a general easterly dip. 



It is then thrown about half a mile east by the N.E. and S.W. 

 faults. The first place where I found it S.E. of the fault was in a road- 

 section leading up from the city towards the Mount ; it crops out 

 on the hill known as Bryniau, and is pierced by the east shaft into 

 the railway-tunnel, and is again seen in projecting ridges N.E. of 

 Want Gwtherin. 



It occurs at intervals N.W. of Llanddeiniolen for about three 

 quarters of a mile, associated with grits, striking N.E. and S.W., 

 almost parallel to the Caernarvon road. It is seen by the road S.E. of 

 Gorphwysfa, where it seems to be twisted over close to the fault, as 

 if an anticlinal had been cut obliquely by the fault. This con- 

 glomerate is made up, as has been stated above, of pebbles in a gritty 

 matrix. The pebbles consist of quartz-felsites, porphyries, a rock 

 like a granite with no mica, all of which can be identified in the 

 underlying series next to be described, and a quartzite, which I have 

 not yet succeeded in finding in place among the undoubtedly under- 

 lying rocks, but which can be matched in a bed occurring among 

 the mica-schists of Anglesey. The pebbles stand out conspicuously ; 

 and where the rock is weathered it falls to pieces, and can seldom 

 be broken across the pebbles. 



Under the grit and conglomerate, which seem to form every- 

 where the basement bed of the Cambrian, we have a series of stra- 

 tified rocks, many of which are of a very marked character, easy to 

 identify and trace, others variable and not very characteristic. Im- 

 mediately to the W. of the east shaft to the tunnel, below the conglo- 

 merate, there are some greenish and purplish beds of schist and tough 

 felsite, breaking with a conchoidal fracture, and ringing under the 

 hammer. Below this there are several beds of breccia, and fine 

 green slate, with the lines of bedding very distinctly marked, and 

 often crossed by small faults healed by the later cleavage. The 

 dip is about 58° S.E. Eurther to N".W. we cross some more green 

 chloritic schists and schalsteins ; but this part of the section is 

 troubled by frequent greenstone dykes, and obscured by talus and 

 remains of drift. Nothing is seen below the conglomerate by Gored 

 Gith, as it there comes against the great fault, and seems to have 

 got turned along it so as to form the cliff almost all the way to the 

 baths near Garth Point. Along the road to Menai Bridge, however, 

 beds of pale altered slate are seen, dipping as though they would 

 pass under the conglomerate. In the corresponding position W. of 

 Bangor Station we find, also dipping under the conglomerate, and, 

 like it, at angles of from 40° to 50°, pale altered slates, below which 

 a brecciated conglomerate is seen, having a very crystalline appear- 

 ance ; and below this there are more pale slates, with an altered grit, 

 in which the quartz appears in sago-like granules. S.E. of Gor- 



