470 PROT. T. G. BONNET ON A SECTION 



26. On a Section recently exposed in Baron Hill Park, near Beau- 

 maris. By T. G. Bonnet, M.A., F.B.S., Sec. G.S., Professor of 

 Geology in University College, London, and Fellow of St. John's 

 College, Cambridge. (Eead May 23, 1883.) 



In the autumn of 1 880 I observed by the roadside leading up the 

 hill from the gates of the Beaumaris Cemetery towards Llandegfan 

 some peculiar grits which reminded me much of certain beds ex- 

 posed in the district near Perfeddgoed House and other places in 

 the neighbourhood of Bangor. The rock, which crops out here 

 and there by the roadside (perhaps about one third of a mile from 

 the road to Menai Bridge) varies from a green " bastard " slate to a 

 grit containing small grains of reddish felsite. These beds are suc- 

 ceeded, after a very short interval, by the normal greenish micaceous 

 or chloritic schists of the region. Although convinced that this 

 indicated an extension of the group of beds which in the Bangor 

 area underlie the conglomerate now generally taken as the base of 

 the Cambrian, such specimens as I could obtain mig^ht not have 

 convinced others, and I waited for a more favourable opportunity 

 of examining the district. Last summer, while on a visit to some 

 friends in the neighbourhood, I was informed by them that a new 

 drive was in process of construction through the woods on the face 

 of the hill mentioned above ; and I applied, as the grounds of the 

 Baron Hill estate are strictly private, to the owner, Sir E. Williams 

 Bulkelcy, for permission to examine the sections. This was at once 

 accorded to me most courteously, and the results proved even more 

 interesting than I had anticipated. 



The new drive is carried along the face of the craggy scarp which 

 overlooks the Menai Straits, and is obviously an old line of cliffs, 

 the base, as we approach Beaumaris, being now separated from the 

 water by a considerable tract of nearly level ground. The drive 

 ascends gradually along the face of the scarp, and crosses by means 

 of a bridge the lane already mentioned close to the outcrop of the 

 aforesaid grits. 



On entering the grounds from the main road, some little distance 

 north-east of the Ferry from Garth, we find greenish and purplish 

 schists, overlain by a compact chloritic schist, which dip at a rather 

 low angle, roughly S.E. Then come other greenish and purplish 

 schists with thinner bands of the more compact rock, followed, yet 

 higher, by a fissile green micaceous schist. This is succeeded by a 

 compact purple variety, traversed by quartz -veins and looking as if 

 silicified. So compact is it in structure that it might readily be 

 mistaken for a flinty argillite. 



These schists may also be seen, though in a condition less favour- 

 able for examination, cropping out by the roadside below, and the 

 last named is identical with a rock exposed in a knoll by the turn- 

 pike, which had always been a great puzzle to me. The dip here- 



