Crystals have often been accidentally produced in the various processes of smelting, having the form and composition, or nearly so, of natural minerals; and have been from time to time described in the scientific journals. Some few, however, which have come under my notice have not been, so far as I am aware, previously described; and as the importance to mineralogy of a due regard to the nature of such crystals, as well as the conditions under which they may have been formed, is beyond question, I avail myself of this opportunity to lay before the Mineralogical Society specimens of the few products to which I allude, and to explain the circumstances of their formation:—

Specimen No. 1 contains some dark green crystals of arseniate of copper, resembling in appearance native olivenite. Before the blowpipe on charcoal these crystals melted easily, then, with a sort of deflagration, gave off copious arsenical fumes incrusting the charcoal, and yielded a button of metallic copper.

Every writer has his moods. It may be thought that the present writer was cynical and severe in his remarks on the geognostic features of Caithness. With a view to remove any such impression, Dr. Maculloch's opinion of that country is quoted ; specially in order that it may be used as a foil to what has to be said concerning the geognosy of Sutherland.

Hear then Macculloch. “On entering into Caithness all the pleasures of travelling are gone and past, for an uglier country from one end to the other would not easily be found. In the usual sweeping manner of those who love to generalise, like Humboldt, it is level, or, at least, not hilly, without trees, without enclosures, as black and as flat as Bagshot Heath ; as flat as a pancake ! Nature has provided no monuments, and has refused to be its poet.

Chemists have long employed the commoner organic acids, especially acetic, oxalic, tartaric, and citric acids in mineral analysis, but with few exceptions they have overlooked the application of these acids to the decomposition of minerals. Acetic acid has been used to separate minerals from their matrix of calcite ; Karsten (Archiv. of Min. XXII, 572) and Sterry Hunt have used it in the proximate analyses of mixtures of calcite, dolomite, and magnesite; calamine and willemite are sometimes distinguished by the gelatinization of the former with the same acid ; Dr. J. Lawrence Smith (Am. J. Sci., [2] XX, 244) has noticed the solubility of anglesite in ammonium citrate ; W. B. snd R. E. Rogers (Am. J. Sci., 1848) have made experiments on the solubility of minerals in water containing carbonic anhydride ; but there is no record of any systematic investigation of the action of organic acids on minerals with a view to the determination of species.

My notice of this must be considered preliminary in every way. The discovery of “the beautiful carnelian marble of Tyree” has been in a late paper credited to Dr. Walker.

For some years after its discovery, it was used, or attempted to be used for mantle-pieces, and other internal decoration.

Partly on account of the minuteness of its pattern unfitting it for this purpose, and partly on account of the small quantity sent into the market, it, however, seems never to have found its way into general favour.

We find Dr. Macculloch lamenting the wasteful method of working adopted in the quarry,—the wholesale shattering of its mass by the excessive use of “Mines.”

I have recently measured one of the crystals of the slag described by by Mr. A. E. Arnold, in vol. III, p. 114 of the Magazine. Observed forms :—

The angles are therefore almost identical with those derived by Miller (Trans. Phil. Soc., Cambridge, III; Brooke and Miller, Mireralogy, 1852, P. 319) from crystals found in refinery cinder, and the slags of copper furnaces, &c, —having the composition of Fayalite, viz.—2 FeO, SiO2.