This historic book may have numerous typos and missing text.
Purchasers can usually download a free scanned copy of the original
book (without typos) from the publisher. Not indexed. Not
illustrated. 1895 edition. Excerpt: ... a traveller for whom the
transport of large fragments has been impracticable, and who has
had himself no opportunity, perhaps not the requisite special
knowledge, for the determination of the petrical characters of the
respective masses. It must be remembered, however, that from the
scientific point of view, the knowledge of a fragment is merely an
aid to the knowledge of the whole; and that the latter necessitates
a determination, not only of the lithical characters of a fragment,
but also of the degree and kind of variation of the lithical
characters throughout the whole mass. As already pointed out, the
whole of a rock-mass is not accessible to observation, and the
lithical characters of all the parts can thus only be inferred from
those observed in fragments broken from the mass here and there, in
quarries, borings, mines and cliffs. A single mass may consist of
more than one kind of rock. It follows from the signification of
the term rock that different parts of a single mass are to be
regarded as belonging to different kinds of rocks, if the parts are
considerable in extent, and their lithical characters, though much
the same throughout each part, show important differences in the
case of the different parts. It would doubtless have been an
advantage if the relationships of such kinds could always have been
indicated in their names. In particular cases, indeed, this is
possible; for instance, one part having certain lithical characters
may be termed basalt, while another part of the same mass, showing
very different characters, may be termed basalt-glass. But such a
mode of nomenclature would only be generally practicable, if a
particular kind of rock, when merely part of a single body, had
always the same kind of relationships, ..
|Country of origin:
British Museum Dept of Mineralogy
||246 x 189 x 2mm (L x W x T)
||Paperback - Trade
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