348 Real and supposed effects of igneous action. 
: g rocks, consist of quartz, glas- 
sy feldspar, augite, hornblende, mica, and olivine, more or 
less blended, and mutually adherent, so as to form solid mas- 
ses. It is impossible to say whether they are the products of 
re-crystallization after fusion, or whether they are ejected 
fragments thrown out from the primitive rocks, lying be- 
neath the bed of the Pacific. They have a strong resem- 
blance to some of the masses ejected by Vesuvius, and per- 
haps it is most probable that they are types of the rocks, 
in which these subterranous and submarine fires of Kirauea 
are fed and sustained. 
os The fragments ? esemblin 
fo, 
4, Among the solid masses are some that very nearly re- 
semble varieties of the Trap Rocks, basalt, and green stone, 
§-c. and if there had been no mistake in associating them wit 
the lava, and other decided volcanic products of these Isl- 
ands, they would go decidedly to sustain the igneous origin 
of the trap rocks. . 
- ..Mr. Goodrich has expressed this opinion very clear in his 
letter, Vol. XI. p. 2. 
5. Obsidian, very brilliant, black and heavy. It is rarely 
quite free from incipient vesicular cavities, which, on the one 
hand, graduate into those that are palpable and large, and 
in the other, becomes evanescent in the solid substance, or 
are discovered only by the microscope. 
6. Olivine, imbedded in large and small masses ; when 
viewed with a magnifier, it is-brilliant and beautiful, with a 
delicate wine yellow color, resembling, in this respect, the 
Saxon topaz ; it appears to be very abundant in the lava of 
Hwauea. 
7. Augite is probably still more abundant, for the melted 
materials often exhibit decisive proof, in the black color, and 
great weight and firmness, of having resulted extensively from 
the fusion of this mineral and hornblende, and there appears 
to have been a large proportion of iron present. 
8. Scorie in vast variety, and in every state of inflation, 
from those pieces that are just beginning to pass from the 
condition of obsidian, and compact lava, into the vesicular 
