194 BASALTIC WONDERS.

siderable size when compared with the height of those of theGiant’s Causeway. The columns of the Venetian groupesdisplay, however, all the varieties of prismatic forms, whichare observable in those of the latter, and other similar groups.They are usually of five, six, or seven sides ; but the hex-agonal form seems chiefly to prevail.

The texture and quality of these columns are not lessdifferent than their forms. Those of the Monte del Dia-volo present a smooth surface, and, when broken, appearwithin of a dark iron-grey colour, manifesting also a verysolid and uniform texture ; in which characters they cor-respond with the columns of the Giant's Causeway, andthose of most other basaltic groups. But the columns ofMonte Rosso are in these respects very different, they hav-ing not only a very rough, and sometimes knotty, surface,but displaying likewise, when broken, a variegated colourand unequal texture of parts. They are commonlyspeckled, more or less distincdy, and resemble an inferiorsort of granite, of which Monte Rosso is itself formed,and which serves as a base to the range of columns inquestion. It is, in general, not quite so hard as the Alpineand Oriental granites, and is sometimes even friable. Thisspecies of granite abounds in France , where large tracts ofit are to be seen in the adjoining provinces of Auvergne ,Vivarez, and Lionnois. But it is still more common inItaly , seeing that, besides Monte Rosso, the bulk of theEuganean hills, of which that is a part, principally consistsof it; and these hills occupy a considerable tract in theplains of Lombardy . It is also common in the Roman andTuscan States ; and of this substance the mountain closeto Viterbo, on the road to Rome , is entirely composed.The columns of Monte Rosso appear, therefore, of a dif-ferent character from any hitherto described by minera-logists, who mention those only of an uniform colour andtexture. But the great singularity here is, that such arange of prismatic columns should be found, bedded as itwere, in a mass of granite, and composed nearly of thesame substance. An instance of this kind, relative to anyother causeway, is not recorded; and this circumstanceseems to render that of Monte Rosso, in one respect atleast, more -curious and singular than the celebrated Giant sCauseway is known to be, from the regular articulation of