168 Miscellanies. 
the birch are in many places distinctly recognizable, presenting much 
the appearance of ordinary agatized woods. At the present time 
none of these plants occur on the island, and we may suppose it 
probable that their destruction was the result of the invasion of the 
silica. 
The numerous thermal springs, in the midst of which the geysers 
are situated, occupy large vallies in the interior of the island. Ap- 
pearances indicate that these waters proceed from deep crevices, in 
which they have been heated by contact with the volcanic fires. 
The geysers present the most magnificent exhibition during an 
inundation of the valley by rain. The rivers proceeding from these 
springs have often the color of milk, owing to the argillaceous bole 
which they take up in their passage over the siliceous deposits. 
Such are the white rivers of Olafsai. 
Mt. Hecla, like all the heights of Iceland, is entirely covered 
with snow. No smoke appeared about its summit. Obsidian oc- 
curs in rolled masses on its sides, and pumice stone forms a bed 
thirty feet in thickness near its base. Fragments of the branches 
of the birch, the remains of the once flourishing forests of the 
island, are found in the midst of this bed. 
After traversing currents of lava of considerable extent, we at- 
rived at the sulphur beds, or solfataras of Krisark. It is literally a 
mountain of sulphur, and is undergoing continual increase— 
Bulletin de la Soc. Geol. de France. T. vii. F. 1—2. Paris, 
1835 a 1836. 
5. From a memoir on the origin of Mt. Etna, by M. Elie de 
Beaumont. (Ed. New Phil. Jour. Ap. 1836.)—It has been as- 
certained that the greater number of the appearances of flames 
which accompany the volcanic eruptions, are only the effect of the 
rays of light which emanate from the incandescent lava, and which 
are reflected by the molecules of vesicular vapor, and of dust dis- 
seminated by the eruption in the atmosphere. In consequence of 
this observation, doubts have been raised as to whether volcanos, in 
any case, produce real flames. ‘These doubts have been already 
removed by Sir H. Davy in regard to Vesuvius, where he ascer- 
tained, during a small eruption, the existence of a real jet of flame; 
and we ourselves have observed on Etna incontestible volcanic 
flames. Having left the Casa inglese about an hour and a half be- 
fore daybreak, in order to ascend to the edge of the crater, the fee- 
