The specimens which form the subject of the present note were brought to England by Mr. H. T. Burls, A.R.S.M., F.G.S., late Geologist to Rajah Brooke, of Borneo.

It was Mr. Burls's intention to communicate to the Geological Magazine the results of his observations in North Borneo, and in this connection I undertook the examination of the limestone with a view to obtaining evidence as to its age. On his departure for South Africa, Mr. Burls left the specimens at the Science Schools, asking me to make what I could out of them without stratigraphical details.

The uppermost limestone stratum of Gotland, which occupies two-thirds of the surface of this island, and is homotaxial with the English Upper Ludlow, contains such numerous fragments of Cephalopoda, that it has been called the Cephalopodan Limestone. Judging from the collection in the Paléontological Department of the Swedish State Museum, the number of species of Cephalopoda from the different strata of Gotland can hardly fall short of 200, most of them in a very perfect state of preservation, some even retaining the surface ornamentation and colour. Amongst them the genus Ascoceras (including Glossoceras), with its nine species, is the most remarkable. As the Museum has succeeded in obtaining specimens showing its morphology more completely than has hitherto been known, a few remarks on it may be made in advance of a monograph now in preparation.

Some new species having been found in the Isle of Wight during the lately renewed examination of its geology by the Geological Survey, and the known Wealden species of that island not having been hitherto so distinctly indicated as might be, it is thought advisable to give some notes on, and a resume of, this interesting series of fossil species.

There are two facts which are closely connected with the present I condition of the Alps—(1) that the rainfall on the Alpine slopes on the Italian side of the watershed, as a rule, is heavier than that on the other side, and (2) that the valleys also are steeper. It is indeed true that the distance from the watershed of the Central Pennines to the lakes on either side, north or south, is not very different, but the level of those on the latter is some 700 feet below that of those on the northern. This difference of level is especially marked in the upper part of the valleys, places correspondingly situated being always lower on the southern than on the northern face; for instance, Zermatt is rather above Macugnaga, but as the crow flies it is more than double the distance from the watershed.

In some cases it is of practical importance to petrologists to estimate the strength of the double-refraction exhibited by doubly-refracting minerals in thin slices of rock under the microscope.

Babinet's compensator, a description of which will be found in Rosenbusch's Microskopische Physiographic der Mineralien und Gesteine, affords a means of accurately calculating the refractive indices of the rays into which light is divided in its passage through doublyrefracting crystals. Michael-Lévy also devised another exact method based on observations made on the tints presented by slices of doublyrefracting minerals, an account of which appeared in the Bulletin de la Societe Mineralogique de France, and which is discussed in a work recently published by Michael-Lévy and Lacroix.

The dyke in question occurs at the extreme north end of Pentreath Beach, which is about a quarter of a mile to the south-east of Kynance Cove.

The dyke forms a portion of the “granulitic group” of Prof. Bonney, which is now known to be of igneous origin, and consists of banded gneissic rocks, some of which are like a granite, other portions like a diorite, the latter always more or less porphyritic.

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.

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.