100 CKOLOGY OF TOICHIXOPOI.Y, &C. [ChAP. IV. 2, 



springs is most developed. Each spring seems to have formed a very 

 low romidish mound, the sides of which consist of the pale browTi tra- 

 vertin, which is in many places permeated by a close net-work of threads, 

 and sometimes by bands, at varying levels, of while inagnesite, 3 to 

 4 inches in diameter. The different and variable thickness of the bands 

 of magnesian sinter may be considered as indicative of periods when 

 the water was more or less highly charged with magnesia in solu- 

 tion. The surface was strewed with fragments of travertin, (many small 

 cavities lined with true botryoidal calcedony of blueish or yellowish 

 colour,) also with masses of coarse jasper. 



At the summit of each mound particularly, the rocks have a very 

 eindery and burnt-xip look, and are very cellular. Their colour is dark 

 reddish-brown, and they are extremely like some varieties of very 

 vesicular lava, or even pumice, in their external appearance. This vesi- 

 cular character most likely owes its origin to the permeation of corrosive 

 gases, as carbonic acid gas. 



There appear to have been altogether six springs. Where the great- 

 est action had taken place, the eastern side was slightly elevated into a 

 small summit with a crateriform depression about 5 feet in diameter, 

 and a few inches deep, the bottom being rug^ged and irregular, and the 

 inner sides nearly vertical. The water which no doubt issued through 

 numerous cracks and clefts in the sides, flowed over and fomied by preci- 

 pitation, on cooling, the travertin-like incrustation before alluded to. 

 This incrustation is stalagmitic in character and appearance, and fills up 

 the cracks and joints of the gneiss, and here and there cements numerous 

 fragments into a breccia, not unfrequently containing grains of chlorite 

 and mica. Here and there on the sides of the mounds are indications of 

 the channels for the off-flow of the water. 



Not the slightest trace of any organism, whether animal or vegetable, 

 could be found in the magnesite, and in the absence of molluscan remains 

 or other clue, no opinion as to the date of activity of these springs 



(322) 



