Since my former paper on the rocks of the Curlew and Fintona districts was published, I have had an opportunity of more carefully examining these districts. Both are eminently favourable for the theoretical geologist, as in them the rocks are much obscured by drift; however, for a careful and painstaking explorer, there are sufficient sections exposed, to show the geological age of the rocks. The accompanying diagram represents the rocks as they occur in the Curlew Mountains district.

Few spots on the face of the globe of the extent of Iceland could be mentioned where, within the same space, an equal number of volcanos could be found. In that island, too, many volcanic eruptions have occurred, which have been, perhaps, of greater magnitude than any others recorded as having taken place anywhere else on the earth. And yet the volcanos of Iceland are but imperfectly known, and, with the exception of two or three, not one of the rest has ever been scientifically examined. Hence the fact, that geological manuals so frequently contain most erroneous statements concerning this subject. A general uncertainty prevails as to how many volcanos have actually been in a state of eruption within historical times; dates are dealt with in a confused manner; and frequently mountains come to figure as volcanos which have never shown any signs of eruptive activity.

In the formation of a country three more or less distinct geological operations are concerned:—a. Rock formation; b. Earth movements; c. Denudation. In the case of our own country, to which the present paper more especially refers, these three operations have succeeded each other again and again; so that a very complicated structure is the result. The earth movements and denudations of one period have been interfered with by those of subsequent periods, and any attempt to trace the exact steps by which the evolution of the British Isles has been effected is therefore attended with very great difficulty.

In these mountains to the north of the road leading from Glen Docherty to Auchnasheen, the gneiss rocks and mica schists of which they are mainly composed dip at a high angle, and have a strike averaging somewhere about N.W. to S.E.—in some places being nearly due N. and S., in others only a little N. of W. This strike, which is the normal one for the Pre-Cambrian rocks, and very unusual in the newer deposits, occurring here throughout so great a thickness of strata and over a wide area, when we take into consideration the fact also that the rocks themselves present the strongest resemblance possible to many of those found amongst the Pre-Cambrian rocks in the Western areas, furnishes very strong proof that we have here a re-appearance of the old Pre-Cambrian floor.

Loch Maree runs roughly parallel with the strike of the beds of the Pre-Cambrian rocks, consequently there is no great thickness of these rocks exposed along its shores, and we do not find the same variability in their character, as in the area previously described. Along the S.W. shores the gneisses described in Notes 4 and 5 are most frequently met with, especially towards the western end; but about the Loch Maree Hotel, and eastward of this point, the gneisses described in Notes 7 and 8 are the prevailing types.

The study of the Palæozoic Tubicolar Annelides has not received that amount of attention which the importance of the Order, either from a geological or zoological point of view, appears to demand. True it is that many interesting and instructive papers and memoirs have from time to time appeared, containing descriptions of species, and occasionally of genera; but, so far as I know, at any rate in this country, no connected account of either Silurian, Devonian, or Carboniferous Tubicolar Annelida has appeared.

On the Graptolites of Gothland (Om Gotlands Graptolither). By G. Linnarsson. Ofv. af. Kongl. Vetens. Akad. Förh.; 1879, No. 5, pp. 12.

The island of Gothland, so rich in all other Silurian fossils, is remarkably poor in Graptolites. Angelin and Lindström simply noted the fact of their presence, but did not attempt their identification. At Dr. Lindström's suggestion, Mr. G. Linnarsson here describes and figures the two species that have been procured from these strata, from examples now in the Riks-Musei of Stockholm.

The following instance of the unconformability of the Keuper and Bunter divisions of the Trias, which came under my notice during the construction of the Great Northern Derbyshire Extension line in the year 1877, is deserving of notice, not only from its decided rarity, but also from its exceptional clearness.

It has often appeared to me that in working out the ancient physical features of the earth in former periods of its history, too little attention has been given to one simple set of evidences which are of wide-spread occurrence, and, frequently, of very clear and decided meaning. I refer to the included rock-fragments of conglomeratic deposits. An appeal to these fragments would, I believe, often bring out clearly-written facts of no small value for the elucidation of the nature of ancient sea-margins, as compared with the much-involved palæontological evidences with which we are made so much more familiar.

Various investigations of the Perlitic structure in igneous rocks have resulted in its being regarded as a product of unequal contraction in a cooling mass of lava. Professor Bonney, in a paper on Columnar, Fissile, and Spheroidal Structure, has compared it to the roughly-concentric joints to which, in certain basalts, the spheroidal character is due; and Mr. S. Allport, in his account of certain Ancient Devitrified Pitchstones and Perlites, writes that “an examination of all the facts leads to the conclusion that the perlitic texture is purely a phenomenon of contraction.” Of this, then, there has practically been no doubt; but, so far as I am aware, the structure has not until recently been imitated by artificial means.

In the present communication I propose to direct the attention of British Geologists to three most valuable memoirs recently published by Mr. G. Linnarsson, the eminent palæontologist of the Geological Survey of Sweden; and at the same time to point out, as briefly as may be, what appears to me to be their special bearing upon certain tentative or disputed points in British Geology. They treat of subjects of great interest to the student of the palæontogeology of the Lower Palæeozoic or Proterozoic Rocks; but are printed in the Swedish language, with which, unfortunately, few amongst us are familiar. The first two papers deal with the Graptolite-bearing rocks of Sweden; the third treats of the peculiar fauna of a recently-detected horizon in the prolific Paradoxidian or Primordial Zone.

In former papers on the Pliocene and Pleistocene Beds near Cromer, an account has been given of the character and succession of these deposits. I have since obtained fuller information with regard to the beds beneath the Boulder-clay, and now give a more complete table, and also venture to propose the subjoined classification of the newer Tertiaries, reserving all details for the Survey Memoir.

The dentition of Gymnura, an existing Insectivorous Mammal, may with advantage be compared with that of the Eocene Carnivora. The dental formula of Gymnura is typical:—

The only other existing Mammals which have 44 teeth are the Pigs and the Moles. But in Eocene times, this number, as first noticed by Professor Owen, was the rule, instead of being the exception.

This paper may be regarded as a notice of those portions of the recently published “Manual of the Geology of India,” by Messrs. Medlicott and Blanford, which describe, or in any way relate to, the extensive lateritic deposits of Peninsular India. The hypothesis (or, more properly, the modification of an antecedent hypothesis) herein offered, in the hope that it may be tested by the Indian geologists, is based on extended examinations of deposits believed to be analogous, and has been found to satisfactorily explain the phenomena observed.

From what we know about the cooling of the earth and its geological structure, it would seem very probable that the principal features which we now see upon the surface of our planet, as, for instance, the continents and ocean-beds, received their forms in very early times, being, in fact, more or less a primary result of contraction. Since the formation of these impressions, contractions have continued to take place, and secondary results have come about, the character of which would appear in a great measure to be dependent upon the primary results by which they were preceded. Amongst the secondary results I would point to the position occupied by many volcanos.

Some twelve years ago I gave (Phil. Mag. March, 1867, “Climate and Time,” p. 548) what appears to me to be the true explanation of that apparently paradoxical fact observed by Mr. Glaisher, that the difference of reading between a thermometer exposed to direct sunshine and one shaded diminishes instead of increases as we ascend in the atmosphere. This led me to an important conclusion in regard to the influence of aqueous vapour on the melting-point ot snow; but recent objections to some of my views convince me that I have not given to that conclusion the prominence it deserves. I shall now state in a few words the conclusion to which I refer.

The rocks described by Mr. Davies in Notes 15–20 belong to the newer series, and were collected as nearly as possible at the points indicated in the sections. They are here described for comparison with the older rocks already referred to, and with the rocks to be further mentioned to the east of this line. I selected intentionally for examination those which appeared most highly altered, or otherwise to have any resemblance to the old rocks; as it is well known that Prof. Nicol considered them to belong to that series, and not to the newer groups. The petrological evidence as given by Mr. Davies proves that they are in no way allied to the gneiss rocks of the old formation, and that they are not sufficiently metamorphosed to be allied to any schists of known Pre-Cambrian age in these areas. These facts, combined with the physical evidence of the discordance in strike also almost everywhere apparent, seem therefore conclusively to prove that they cannot be of Pre-Cambrian age, but that they belong to a much younger series, and overlie the limestone group found along the west side of Glen Laggan.

These caves, whose original mouths are now probably destroyed or concealed by rubbish, open at present into a quarry in a limestone knoll on the townland of Carrigagower (‘ Rock of the Goat’), three or four miles south of Middleton. They are not broad nor lofty, but have extensive ramifications, especially that one which opens into the north-west part of the quarry. At its eastern end, and at a depth of 20 feet from the surface, the quarry is crossed by a cave now exposed by the removal of its western side. This cave runs in the line of a joint or fissure, and penetrates the rock north and south.