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ranged granite, gneiss, porphyry, amygdalite, bricia, and sand-stone; and the reader will be surprised to find what various and discordant objects are united under these vague appellations. Mr. Kirwan has, in like manner, two titles of Aggregated and Derivative Stones; the other rocks being considered under the simple substances.
Daubuisson supplied Brochant with a short account of rocks upon the plan of the Wernerian geology, or, as it is called, geognosy, not by the most fortunate term, for the Gnostics have been celebrated for sixteen centuries as only pretenders to knowledge. But Werner is, on the contrary, the most able and sagacious observer that the science has ever produced; and his observations will continue valuable to the latest posterity. His reputation cannot be injured even by the insolent tone of his disciples, who seem to say, "Are we not sons of the wise, and shall not knowledge die with us?" Daubuisson has however treated this subject with great modesty and accuracy. The fault in the plan is,
that it is theoretic, and constructed upon geological ideas of the antiquity and formations of the several rocks; which the successive and general observations of future ages may perhaps demonstrate to be only local, or erroneous; and which, even at present, are very far from being universally admitted. Nay, if they proved to be infallible, or uncontrovertible by any future facts or arguments, still the plan of arrangement would be improper for a truly scientific work, the same substances being repeated as primitive, transitive, and secondary, nay, sometimes of independent formations; while, in any science, all that is required is the knowledge of the object collected into one strong point of view. The denominations are also, as in the instance of porphyries, so lax and vague, that the very base and nature of the substance are confounded, and no accurate knowledge can arise. In any science, on the contrary, it is necessary that the objects be classed, and most precisely defined, before even a plausible system can be con
structed the stones must not only be hewn out of the quarry, but most accurately squared, before the temple can be erected. But true science and theory are so completely opposite, that any attempt to blend them has always defeated its object.
To Mr. Jameson we are greatly indebted for a more ample account of the Wernerian theory of rocks, which he has illustrated with considerable care and attention, so as to form by far the most complete treatise on the subject which has yet appeared. But an infinite number of rocks occur in nature, which have neither name nor local habitation in the Wernerian system, nor in the Huttonian; though no science can be called complete without enumerations of all its objects, and in the present instance one neglected rock might perhaps suffice to overturn a theory. The greatest misfortune in the progress of human knowledge has always been, that theories have been constructed before facts have been observed. The theories are indeed useful,
as they stimulate their admirers to the observation of facts; and as Werner himself observed to the author at Paris, a theory is useful to concatenate facts, and render them more clear and pleasing to an audiNor, with the modesty of a man of real genius, did he conclude his own theory
to be unobjectionable.
The intention of this treatise is the accu- Intention of
rate knowledge of rocks considered in themselves. As a Zoologist or a Botanist does not pretend to discriminate which plants or animals are of early or of later creation; and, in the other branches of mineralogy, it is neither the situation nor antiquity of the gem, or the metal, that is an object of the science, but the nature and name of the substance itself. A Gemmologist would be ridiculed if he could not distinguish a blue diamond from a sapphire, without a previous acquaintance whether the object came from Golconda or Pegu; and a Metallogist must distinguish grey silver ore from antimony, without knowing either its formation or site. In the same manner a knowledge
of rocks, arising from local relations, must always be regarded as empyrical, and will often prove wholly erroneous. That great Saussure's observer, Saussure, found, in the ample scene of the Alps, that he was farther removed from the formation of a theory, after the sedulous labour of forty years, than at the beginning; that instead of any regular plan or order, he found perpetual contradictions, in the assemblage and coalescence of substances, that seemed to be wholly remote and dissimilar. " It may well be affirmed," says he, "that there is nothing certain in the Alps, but their variety. . . . . Sometimes the skirts are calcareous, sometimes magnesian. The cen tres and highest summits are here of massive granite, there of a calcareous mica slate; sometimes of magnesian stones, sometimes of gneiss if the beds be considered, here they are vertical, there horizontal; here their inclination follows the slope of the mountain, there quite the contrary."* We may add, from more recent observations,