The material of which most of these islands are composed is chlorite schist, but as this rock is almost always distinguished by the quartz veins which intersect it, so in this case some of the islands are composed of this material almost exclusively, which gives them a very striking white appearance. One of these, containing the principal inscriptions, is called Miles island. The figures, which covered every part of the rocks that were exposed, were apparently of historical or at least narrative purport, since they seemed to be connected. Doubtless the larger portion of the inscription has been carried away by the successive vicissitudes which have broken up and defaced, and in some instances obliterated, parts of which we find evidence of the previous existence on the islands. Every large bowlder seems to contain some traces of previous inscription, and in many instances the pictured side of the bowlder is on its under side, showing that it has been detached from its original place. The natural agencies are quite sufficient to account for any amount of this kind of displacement, for the rocks in their present condition are not refractory and offer no great resistance to the wear of weather and ice; but in addition to this must be added human agencies. Amongst other things, they represent the conventional Indian serpent’s head, with varying numbers of lines. Some of the signs next frequently recurring were concentric circles, in some cases four and in other cases a lesser number. [Illustration: FIG. 45.--Bald Friar rock, Maryland.] Fig. 45 is a reproduction of Prof. Frazer’s illustration. This region was also referred to by Dr. Charles Rau (_a_), his cut from the specimen in the collection of the Smithsonian Institution (Mus. No. 39010) being here reproduced as Fig. 46. [Illustration: FIG. 46.--Slab from Bald Friar rock, Maryland.] During the autumn of the years 1888 and 1889 Dr. Hoffman visited these rocks, securing sketches and measurements, the former of which are reproduced in Figs. 47 and 48. The figures are deeply cut, as if rubbed down with sand and a round stick of green wood. The deepest channels, varying from three-fourths to 1-1/4 inches across and almost as deep as they are wide, appear as if cut out with a gouge, and for this reason bear a strong resemblance to the petroglyphs in Owens valley, California. In whatever manner these sculpturings were made, it is evident that much time and great labor were expended upon them, as this variety of rock, locally termed “Nigger-head,” is extremely hard. [Illustration: FIG. 47.--Top of Bald Friar rock, Maryland.]