It remains for future
inquirers to determine how transformation can have been effected without
contact with the endogenous stone, where strata of dolomite are found to be
interspersed in imestone. Where, in this case, are we to seek the concealed
channels by which the Plutonic action is conveyed? Even here it may not,
however, be necessary, in conformity with the old Roman adage, to believe
"that much that is alike in nature may have been formed in wholly different
ways." When we find, over widely extended parts of the earth, that two
phenomena are always associated together, as, for instance, the occurrence
of melaphyre
p 265
and the transformation of compact limestone into a crystaline mass differing
in its chemical character, we are, to a certain degree, justified in
believing, where the second phenomenon is manifested unattended by the
appearance of the first, that this apparent contradiction is owing to the
absence, in certain cases, of some of the conditions attendant upon the
exciting causes. Who would call in question the volcanic nature and igneous
fluidity of basalt merely because there are some rare instances in which
basaltic veins, traversing beds of coal or strata of sandstone and chalk,
have not materially deprived the coal of its carbon, nor broken and slacked
the sandstone, not converted the chalk into granular marble? Wherever we
have obtained even a faint light to guide us in the obscure domain of
mineral formation, we ought not ungratefully to disregard it, because there
may be much that is still unexplained in the history of the relations of the
transitions, or in the isolated interposition of beds of unaltered strata.
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