VTA WSL AN ODIS. 347 
The fragmentary recks have sometimes a very doubtful aspect, and 
any but their true origin would be suspected by one unacquainted 
with the locality. One of the most singular varieties was collected 
by Lieutenant Walker, on the northeast shores of Vanua Lebu. It 
consists of a fine greenish base, of an arenaceous aspect, containing 
thickly disseminated grains of quartz, many of which are in regular 
crystals, partially rounded. ‘The crystals are bipyramidal dodecahe- 
drons, averaging an eighth of an inch in diameter; and excepting the 
little attrition they have undergone, some of them are perfect. They 
are associated with a few fragments of a glassy feldspar and some 
minute crystals of sphene. ‘The greenish base is soft, and fusible 
before the blowpipe. It appears to have the same nature with the 
base of the Mali pumice-conglomerate, and is probably derived from 
a decomposed trachyte, or some allied feldspathic rock. Excepting 
the fusibility, and some few minute pebbles imbedded, it closely re- 
sembles certain specimens from granitic regions. 
The mud brought up from the bottom, in the channel to the south- 
west of Viti Lebu, contains numerous rounded pebbles of quartz ina 
grayish gritty base. The appearance of it would suggest any but a 
basaltic origin, and it certainly authorizes a suspicion that either granite 
or sandstone may occur on the large island. When dried, the speci- 
mens strikingly resemble a common grit rock, like many in the car- 
boniferous series. ‘The base contains many opaque white particles 
and pebbles, appearing to be feldspathic. ‘The quartz is mostly white 
and translucent, but other pebbles are of rusty yellow and brown 
colours, and opaque. We are inclined to believe that the constituents 
of this mud have been derived from the basaltic rocks: yet if must 
be admitted to be just the kind of mud which might be expected 
in a sandstone or argillaceous sandstone region. ‘The geodes in the 
basaltic rocks, and the silicious veins which intersect it, may have 
afforded the quartz, and the other materials may come from the de- 
composition of some basalts. The specimens show the necessity of 
great caution in deciding upon the origin of the materials of sedimen- 
tary rocks. 
From the above, it appears that the proportion of compact basalt 
in these islands is.very large. No lava stream was observed, and 
no cone was examined on the two large islands, which could have 
been a centre of volcanic eruptions, although we can scarcely doubt 
that such cones must exist in some parts of the group. Many a 
