and it affords an excellent example of the errors which arise in geological reasonings, from an ignorance of the true characters of minerals and rocks. On exa mining the specimens found in collections,called Hun garian pitchstones, it will be seen that the greater number consist of this jasper. It should be super fluous to remark, that the same substances occur where trap veins pass through strata capable of under going the same change. In the claystones of the trap family, the progress of induration is commonly such as to cause them to pass, through various stages, to compact felspar, as it is commonly called. But, in certain situations, the same claystones are found passing into jasper; being highly indurated, without acquiring the peculiar character of compact felspar. This alteration seems to occur chiefly among the older claystones and porphyries which accompany granite; and there is no difficulty in tracing its progress, even into the porphyries them selves, as the cause must also be obvious. Thus there arc formed porphyries with a base of jasper : while, as in every other case of such transitions, specimens of doubtful character become the inevitable conse quence. Such jasper also occurs among the secon dary claystones when in contact with masses or veins of other traps ; and lastly, as irregular masses among the primary rocks, occupying situations analogous to porphyry or claystone, but presenting no transitions into these, by which to indicate an identity of origin. If nevertheless it is probably the same, we are yet in want of information on this part of the subject. It is thus apparent, that jasper belongs, indifferently, both to the primary and secondary divisions ; but it would be a needless nicety, in this as in other cases, to form two distinctions.