Now, if it can be made to appear, that there is
no solid ground for this distinction; and if it can be shown, that there
is truly no mineral body in this earth which may not have been produced
by operations natural to the globe, we should thus procure a certain
confirmation of the doctrine. This also will be the more interesting,
in being deduced from a part of natural appearances, which seemed to be
inconsistent with the theory.
Certain masses or mountains of granite, are the only bodies of this
earth which have apparently a certain pretension to this species
of originality. These, therefore, must be now the subject of our
examination.
Granite, considered by itself, does not appear to have any claim to
originality in its nature. It is composed of bodies which are capable of
being analyzed; and these are then found to be compositions of different
substances, which are also sometimes variously proportioned. The
feldspar and the mica, for example, as well as the schorl, are found
variously coloured in different granites, and coloured in various
proportions. Besides the variety in the composition, or chemical mixture
of the different bodies which compose granite, this rock admits of a
great diversity, from the variety of its mechanical mixture, or from
the different species of bodies which are its constituent parts.
Pages:
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297