94 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [DcC. 18, 



2. On the Geological features o/.^/^e Northern pari 0/ Formosa, 

 ayid of the adjacent islands. By Cuthbert Collingwood, M.B., 

 F.L.S. 



(Communicated by the Assistant-Secretary.) 



[Abridged.] 

 The west coast of Formosa is generally very flat, consisting of low 

 alluvial plains for the most part, the monotony being broken here 

 and there by a hill, which forms an important landmark. Such is 

 the coral hill known as Apes' Hill, 1110 feet, marking the entrance 

 to the port of Takau-con, on the south-west coast ; and such are the 

 two prominent peaks of Kwang-yin and Tai-tun (1720 and 2800 feet 

 respectively), between which is situated the harbour of Tamsuy, on 

 the north-west coast. Both of these are treaty ports. Besides these, 

 there is no conspicuous elevation immediately upon the west coast. 

 This coast, in all its middle portions at least, has been placed, during 

 the present visit, by Commander Bullock, of H.M.S. " Serpent," 12 

 miles further west than appears on the most recent charts, thus very 

 materially narrowing the passage between it and the Pescadores, 

 known as the Formosa Channel. The only place where the hills 

 approach this coast is in lat. 24° 15', where there is some tableland 

 which is denuded into picturesque valleys at right angles to the 

 shore. It is well known, however, that a considerable range of 

 mountains runs nearly through the island from north to south, of 

 which Mount Morrison is the culminating point. These mountains 

 approach the east side of this island, and for the greater portion 

 of it render it harbourless and inhospitable, the steep sides of the 

 mountains running sheer down into the sea. 



At Tamsuy, in the north-east of the island, the right bank of the 

 river upon which the town stands rises to the height of about 100 

 feet or upwards, in an undulating manner, and is entirely composed 

 of alluvial clay, containing a vast number of boulders of stone. 

 These boulders are of the most various sizes, from such as could easily 

 be lifted by the hand to large blocks of 20 feet in circumference. 

 They are alio of very varied forms, some being round and smooth, 

 and evidently more or less rolled, while others are quite angular, 

 and have little or no appearance of having been waterworn. I ex- 

 amined many of these blocks to see if I could discover any traces of 

 striation which could be attributed to glacial action ; but although 

 I met with suspicious markings, I could not satisfy myself that they 

 were due to the action of ice. Moreover there is no marked differ- 

 ence in the various boulders as to lithological character ; but to aU 

 appearance they were all, with little variety, of the ordinary green- 

 stone, though I am not in a position to say whence they are 

 derived. Their presence and character, however, appeared to me at 

 least remarkable, and worthy of further investigation. 



Higher up the river, which in the main flows from east to west, 

 the hills rise on the north side from an alluvial plain, and consist in 

 their lower portion of a calcareous grit, which crops out from the 

 grassy slopes in great angular blocks, having an inclination of 15° to 



