crystallised feldspar, numerous grains of quartz, and brilliant, though
small, crystals of hornblende. The feldspar and hornblende in this and the
succeeding cases have been determined by the reflecting goniometer, and the
quartz by its action under the blowpipe. The feldspar in these ejected
fragments, like the glassy kind in the trachyte, is from its cleavage a
potash-feldspar.

SECONDLY, a brick-red mass of feldspar, quartz, and small dark patches of a
decayed mineral; one minute particle of which I was able to ascertain, by
its cleavage, to be hornblende.

THIRDLY, a mass of confusedly crystallised white feldspar, with little
nests of a dark-coloured mineral, often carious, externally rounded, having
a glossy fracture, but no distinct cleavage: from comparison with the
second specimen, I have no doubt that it is fused hornblende.

FOURTHLY, a rock, which at first appears a simple aggregation of distinct
and large-sized crystals of dusty-coloured Labrador feldspar (Professor
Miller has been so kind as to examine this mineral. He obtained two good
cleavages of 86 degrees 30 minutes and 86 degrees 50 minutes. The mean of
several, which I made, was 86 degrees 30 minutes. Professor Miller states
that these crystals, when reduced to a fine powder, are soluble in
hydrochloric acid, leaving some undissolved silex behind; the addition of
oxalate of ammonia gives a copious precipitate of lime. He further remarks,
that according to Von Kobell, anorthite (a mineral occurring in the ejected
fragments at Mount Somma) is always white and transparent, so that if this
be the case, these crystals from Ascension must be considered as Labrador
feldspar. Professor Miller adds, that he has seen an account, in Erdmann's
"Journal fur tecnische Chemie," of a mineral ejected from a volcano which
had the external characters of Labrador feldspar, but differed in the