This narrow stream is to be traced across the strata for more than a league and a half; and the whole appeared to Faujas so marvellous, that he says he almost doubted the testimony of his senses. He would have done much better, however, to have doubted the conclusions of his theory; for it was by them that the phenomena before him were rendered so mysterious and incredible. While he continued to regard what is described above as a stream of melted lava, which had descended from the top of one mountain, and climbed up the sides of the opposite, like water in a conduit pipe, piercing occasionally through vast bodies of solid rock, it is no wonder that he considered as marvellous what is indeed physically impossible. Had his belief in the volcanic theory permitted him to see in all this, not a superficial current, but one of indefinite depth, he would have beheld the object divested, not of what was curious and interesting, but of what was incredible or absurd, and reduced to the same class of things with mineral veins. That it belongs really to this class, and is no more than a vein or dike of whinstone, intersecting the strata to an unknown depth, and most probably, like other veins, communicating with the mineral regions, cannot be doubted by any one who has studied the subject of basaltine rocks, through any other medium than the volcanic theory. The ramifications which run from it into the calcareous rock, contrived, Faujas says, just as if on purpose to perplex mineralogists, is one of the well known and characteristic appearances of basaltic veins. 242. It can hardly be doubted, that the lava described by the same author as heaving up a mass of granite,[127] and including pieces of it, is a rock of real whinstone. The same may be said of many others; and, though I pretend not to affirm that there is nothing volcanic in the Vivarais, I must say, that nothing decidedly volcanic appears in the description of that country, but many things that are certainly of a very different origin. [Footnote 127: Volcains Eteints du Vivarais, fol. p. 365, &c.] In the present state of geological science, a skilful mineralogist could hardly employ himself better, than in traversing those ambiguous countries, where so much has been ascribed to the ancient operation of volcanic fire, and marking out what belongs either clearly to the erupted or unerupted lavas, and what parts are of doubtful formation, containing no mark by which they may be referred to the one of these any more than the other. Such a work would contribute very materially to illustrate the natural history of the earth.