flinty matter by deposition from water is a daily occurrence, there is no reason to doubt that they may be specimens of plants now actually existing. But it is also necessary to consider their geological connexions before a full answer can be given to such a question. This is unfortunately attended with considerable difficulty, as the greater number of specimens are only to be found in the hands of lapidaries and jewellers, in circumstances which render it impossible even to trace the country from whence they have been brought, and much less the geological situations in which they have occurred. I have only one meagre fact to offer on this subject. I have said in the commencement of this paper, that many of the specimens found at Dunglas contain remains of vegetables. These specimens appear to have been detached from a breccia inferior to the lowest sandstone, of which a part is visible at St. Abb's Head, and which is probably a portion of the extensive breccia found in so many parts of Scotland, interposed between the primitive rocks and the whole series of flœtz strata. These then contain remains of organized substances of an epocha at least equally ancient with that in which the vegetable remains found in the flœtz strata existed. As the species ascertained by Daubenton have in all probability been preserved in recent formations of chalcedony, so it is probable that those which I am now describing have been preserved in the chalcedonies of former days.
It is said that chalcedonies of this nature are found in the Dutchy of Deux Ponts, in Siberia, and in other situations, but there is no information sufficiently accurate respecting these on which to ground any reasoning. I ought however, to add, that in many of the Siberian specimens which are known to lapidaries by the name of Moss agates, I have ascertained by chemical means that the green fibres consist of chlorite.
It would indeed have been unpardonable not to have used the aids
