Mr Menge's Mmerahgical Journey in Iceland, 157 
Iceland, were formerly continuous with it ^ ; and was informed 
that the volcano of Heima-Ey, in one of the Westmanna Islands, 
was formed probably by a subterranean communicating canal, 
during an eruption of Eyafialla-Jokull. 
On the latter, as well as in the former, I observed three diffe- 
rent streams of lava, separated from each other by layers of trass, 
which appear to have been formed after the eruption of the la- 
va, by ejected masses and volcanic ashes. In the lowest bed, 
which is a porphyritic lava, I observed imbedded fragments of 
granite, gneiss, and syenite. The examination of these fused 
porphyritic rocks, made me fancy myself transported to the 
Lake of Laach, on the banks of the. Rhine ; but as I expected 
to find all the productions of Vesuvius and the Lake of Laach 
on the mainland of Iceland, I did not delay to search for them 
in this quarter Although the trap-rocks ( thcmage massen- 
ney of great difficulty and of much danger. He examined the north coast of Ice- 
land from Skagafiord to Myvatn, and from Myvatn he proceeded eastward to Vopna- 
fiord, and then south-east to Eskefiord, Berafiord, and Hammersfiord. He took his 
departure from Eskefiord on the 4th October, in a vessel bound for Copenhagen, 
but which put into Leith, in order to discharge part of the cargo, when we had the 
pleasure of making his acquaintance. During our conversations with him, we found 
that he had seen and examined more of the mineralogical structure of Iceland than 
any of those travellers who had preceded him. We expressed a wish to have a 
short account of his journey, and Mr Menge transmitted to us in German the com- 
munication of which we now present a translation to our readers. — E d. 
• According to Menge, there is a ridge of rocks, extending under the sea from 
the Westmanna Islands to the mainland of Iceland, — a fact illustrative of the opi- 
nion in regard to their former connection stated above. — E d. 
-)• We insert the following notice respecting the Lake of Laach, in order that 
our readers may understand the allusion to it in the text. Trap, or volcanic tuffa, 
abounds around the lake, and incloses balls of porphyry-lava OlViA felspar-lava. The 
first, or porphyry-lava, contains abundance of glassy felspar, mica, olivine, augite, 
and fragments of burnt grey-wacke, which pass into a kind of pumice : the second, 
or felspar-lava, is a mixture of felspar and hornblende, and contains titanite, octa- 
hedral magnetic iron-ore, haliyne, iolite, sodalite, nepheline, &c. Around the lake, 
streams of hasaltic-lavaj are to be seen. At Niedermennich, there is a quarry of this 
lava, which is used for mill-stones. A few miles from the lake, there is a whole 
hill of tuffa, containing numerous beds of leucite-porphyry, in which there occur 
imbedded mica, sphene, and glassy felspar. Underneath these volcanic rocks, lie por- 
phyry-slate, and various other trap-rocks ; and these again rest on grey-wacke, that 
rock on which all the trap-rocks along the Rhine rest. The Lake of Laach itself 
appears to be the crater of an extinct volcano. — Ed. 
3 
