Journey through North, South and East Iceland. 159 
appear confusedly aggregated together. In transverse sections, 
the lava presents five, six, or seven sided columnar concretions 
The mass or rock is compact, and differs but little from basalt. 
This kind of lava, which may be named hasalt-lava, has often 
flowed to a considerable extent, sometimes with a smooth surface, 
sometimes with a surface resembling that of water when a 
gentle breeze begins to blow over it. Further, it is cavernous, the 
hollows or caverns appearing to have been formed by internal 
heat during the cooling of the surface of the lava. The se^ 
cond terrain is generally either in waves, or the rock appears 
heaped together in masses, having a rough, denticulated, 
and knotted surface, which we cannot behold without horror, 
and over which it is impossible to travel more than four or five 
miles. The third terrain is formed of spumous lava, which is 
sometimes rolled into long and large cylindrical masses. Its co- 
lour is grey and red, and although much ironshot, is light. In 
this lava, we observe numerous small rose-like forms, with small 
craters in the middle, through which the flame had issued. 
From Hilleraa to Reikiavig, onwards to Vidoe, Essian and 
Mossfell, all appears to be unmelted; yet the rocks are not without 
marks of the action of heat. Even in the neighbourhood of Hav- 
nefiord, I observed a felspar lava, (greenstone), with druses con- 
taining ice-spar and augite crystals. I afterwards found this rock 
frequently alternating with trap rocks, — a circumstance which 
proved, in my opinion, that this lava had not flowed in the form 
of a stream, but had been changed on the spot by the action of 
fire. The mass of the rock was more compact all around Rei- 
kiavig, and appeared as basalt at Vidoe. The amygdaloid for- 
mation, with alternate beds of wacke, basalt, trap-porphyry, 
greenstone, &c. first appears at Essian. This formation is often 
traversed by veins, which are principally of compact basalt, ob- 
sidian, greenstone, and which sometimes contain a quartz which 
includes iron-pyrites. The beds frequently contain jasper, opal, 
zeolite, and calcedony. At Mossfell, there are beds and veins 
of an obsidian-breccia, which passes into basalt-tuffa. 
* The fact of stream-lava occurring in columns like basalt, has been denied by 
many naturalists; but the observations of Menge appear decisive as to this point.— 
Bo. 
