I Have been very much interested in reading Mr. Russell's two communications published in the Geological Magazine for August and September last. The analogy which he draws between the history of the Dead Sea valley and that of some of the lake valleys in the western part of North America is instructive as showing how similar physical features can be accounted for on similar principles of interpretation over all parts of the world. Mr. Eussell very properly draws attention to the paper by his colleague Mr. G. K. Gilbert on “The Topographical Features of Lake Shores,” in which principles of interpretation of physical phenomena are laid down applicable to lakes both of America and the Jordan-Arabah valley. With some of Mr. Russell's inferences regarding special epochs in the history of this valley I am very much disposed to agree; more particularly in reference to the mode of formation of the Salt Mountain, Jebel Usdum; or rather, of the salt-rock which forms the lower part of its mass. If this interpretation be correct, it removes the difficulty of understanding why the rock-salt is confined to one small corner of the lake, which, at the time the salt was in course of formation, was vastly more extensive than at present.

The following notes have been compiled in order that, pending the publication of the results of microscopic and chemical examination of the specimens collected, geologists visiting the island may have an accurate localization of the dykes and intrusive sheets bearing glassy selvages observed by the writer and Mr. J. Lomas, A.N.S.S., during a recent visit to Mull. The list includes, for the sake of completeness, three occurrences of tachylyte which have already been described, viz.:—Some and Gribun1 and Ardtun.

In the Geological Magazine for November last (Decade III. Vol. IV. p. 481, Pl. XIII.) I gave a brief description of a new species of Eurypterus from the Lower Carboniferous Shales, Eskdale, Scotland, which I named Eurypterus scabrosus.

I referred to other Carboniferous forms, and briefly mentioned one from the Lower productive Coal-measures, Darlington, Pennsylvania, U.S.A., figured as a woodcut only in the American Phil. Soc. Proc. vol. xix. p. 152, 1881.

These specimens were collected in Socotra, near the coast, by Colonel M. Gosset, and were sent to Prof. Rupert Jones. By the kindness of Prof. Bonney I have been allowed to carry on the examination of the rocks, at University College, in connection with the Somali specimens already described.

These notes are intended as an appendix to “Notes on the Erosive Power of Glaciers, as seen in Norway” (vide this Magazine, Decade III. 1887, Vol. IV. No. 4, p. 167).

1. The object of my visit to Norway and the Alps was to leave closet-geology in America, in order to make personal observations of the phenomena associated with modern glaciers,—for comparison with those in the region of our Great Lakes, often attributed to land-ice.

In a Memoir recently published “On the Fossil Fish Remains of the Tertiary and Cretaceo-Tertiary Formations of New Zealand” (Transactions of the Royal Dublin Society, vol. iv. ser. II. p. 11, pl. vi. fig. 22) there is described a small tooth as an immature example of Carcharodon angustidens, Ag. The specimen was included amongst a large number of others forwarded for examination by Sir James Hector, Director-General of the Geological Survey of New Zealand; it is a small tooth, exquisitely preserved, and does not exhibit any signs of abrasion by use, which led to its being provisionally considered as the tooth of a young shark, and its form and minutely serrated margin appeared to indicate that its relationship was with Carcharodon.

As Professor Blake, in his elaborate paper in the Quarterly Journal of the Geological Society for August last, makes frequent reference to my work in Anglesey, I may perhaps be permitted a brief comment. I do not intend to enter upon an elaborate controversy, since I prefer, now that the two views of the district have been published, that those interested in the matter should visit the ground, and judge for themselves. Nevertheless, it is well that the salient points of agreement and difference between the two readings should be placed in a clear light.

In “Nature”, August 26, 1886, vol. xxxiv. p. 387, I ventured to draw a distinction between the outliers of unfossiliferous Tertiary sands found at high altitudes on the North Downs and the deposits containing casts of fossils of Pliocene age which are found in hollows in the Chalk at Lenham. Last summer I visited and examined, I believe, all the more important outliers of the former series, Mr. J. Hutchins French, F.G.S., having kindly conducted me to those at Headley and Chipstead; those at Netley were visited with other members of the Geologists' Association under the direction of the same gentleman.