98 • PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 18, 



first of these. Pinnacle Island, is a perfectly bare, craggy rock, 

 with a pinnacle at either end. The rock was whitened with the 

 dung of sea-birds ; and as we could not land, I was unable to deter- 

 mine with certainty its mineralogical composition. 



The other two I had better opportunities of observing. The 

 whole of Craig Island is a mass of trachytic lava broken up into 

 smalHsh rough masses, even to the very summit. These blocks, 

 upon the seashore, are very large, and piled up in picturesque confu- 

 sion. On the eastern side is a series of pinnacles, or aiguilles, form- 

 ing natural arches. They appear to be portions of a trap -dyke 

 running out into the sea. 



The third island of this group is Agincourt Island, the appearance 

 of which is very remarkable from the numerous caves in its sides 

 visible at a considerable distance ; and its structure is on a near 

 inspection easily discernible. The island is a rounded hill of sand- 

 stone with several smoothly worn eminences, but traversed by an 

 enormous dyke of trappean rock. This dyke, seen best on the 

 north side, is broad and nearly level, terminating in an abrupt 

 precipice on the left, and gently sloping to the sea on the right 

 hand. It cuts off a small portion of the sandstone rock from 

 the main mass; and in this portion are two conspicuous caves. 

 There are no less than six caverns in this island, nor are they all 

 confined to the soft sandstone; two of them are in sandstone on 

 the north side, and two in the sandstone of the south side. In all 

 these the arches were broad and sweeping. The other two caverns 

 were situated in the face of the trap -cliff of the eastern side of the 

 island ; and these were lofty and irregular in form, and quite dis- 

 tinct in character from the rest. 



Eeyond these, seventy-five miles to the eastward, is another 

 group, consisting of Tia-usu,Hoa-pinsau, and Pinnacle Island, form- 

 ing one group, of which the first named is composed of trappean 

 rocks with a bold outline and rising nearly 1200 feet high; and 

 Pinnacle Island derives its name from the remarkable forms which 

 the most elevated and prominent rocks assume, and which have all 

 the aspect of buildings, lighthouses, &c. 



3. On some Soitrces of Coal in the Eastern Hemisphere, namely 

 Formosa, Labfan, Siberia, and Japan. By Cuthbert Colling- 

 wooD, M.B., F.L.S. 



(Communicated by the Assistant-Secretary.) 



[Abridged.] 



The Formosa coal-district is situated near Kelung, in the north- 

 east corner of the island. The mines are a little more than a 

 mile to the eastward of the town, upon the hills bordering on 

 Quar-se-kau Bay. I approached them in a small boat up a muddy 

 creek. On leaving the boat, we ascended a slight elevation passing 

 a range of red sandstone hills, which formed a series continuous 



