382 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [JunO 19, 



10. The Sulphur-springs 0/ Northern Formosa. 

 By Cuthbert Collingwood, M.B., F.LS. 



[Communicated by Dr. J. D. Hooker, F.E.S., F.G.S.] 



I lately had an opportunity afforded me, by a cruise in H.M.S 

 * Serpent,' Commander Bullock, of visiting the remarkable sulphur- 

 springs in the neighbourhood of Tamsuy, in the north-east part of 

 the island of Formosa. These springs are situated among the hills 

 about equidistant from Tamsuy (or Hoowei) and Mangka, the capital 

 of the Tamsuy district, and are highly interesting from a geolo- 

 gical point of view, indicating as they do the existence of volcanic 

 action near the surface in these regions — a circumstance which we 

 might have been led to expect from the frequent occurrence of 

 earthquakes. 



The sulphur-springs which I am about to describe are not the only 

 springs of the kind in those parts ; others are indicated at no great 

 distance. The road to them runs through a beautiful and highly 

 cultivated district. Besides numerous paddy-fields situated upon 

 the hillsides, and ingeniously irrigated by a series of platforms, 

 down which the water flows from one to the other after the manner 

 of the cascades of St. Cloud, a remarkable feature is an immense 

 pineapple-plantation of many acres in extent ; so that the verdure 

 of these hills leaves one unprepared for the fact of subterranean 

 heat finding a vent in such close proximity. 



About halfway up the ascent we cross a stream having the cha- 

 racter of a mountain-torrent, the stones at the bottom of which are 

 covered with a deep -green deposit, very copious in the quieter and 

 more sheltered spots ; and upon dipping one's hand into thiis stream, 

 the temperature is found to be too high to allow it to remain there. 

 At this point it was about 130° ; but higher up it could be seen 

 steaming, notwithstanding the tropical heat of the day. 



This stream does not appear to flow directly from the sulphur- 

 springs above, but probably from some subterranean source con- 

 nected with them. The channel leading down directly from the 

 springs is quite dry, though it bears evidences of having been, com- 

 paratively recently, the theatre of similar exhalations. The rocks 

 over the opposite side of this ravine are lofty, and crop out boldly, 

 striking south-east, and dipping down to the north-east in the 

 direction of the springs. At this spot they have a bleached ap- 

 pearance, visible from a distance, precisely similar to that exhi- 

 bited at the active springs. They bear, however, at this present 

 moment, no other sign of their past activity ; but, on a near ap- 

 proach to them, a very perceptible odour of sulphuretted hydrogen 

 is smelt, and the rocks themselves appear to have their surface dis- 

 integrated by the action of the steam. 



A short distance above this spot we reach a cul-de-sac in the 

 hills, bounded on the right by bold bare rocks, having the litho- 

 logical characters of a coarse calcareous grit, and dipping about 15° 

 to the north-east. This is the spot occupied by the present active 

 sulphur-springs, and is of small extent, embracing not more than 



