The present nomenclature of igneous rocks is generally acknowledged to be unsatisfactory, for not only is it without useful meaning, but it is also so unsystematic that it forms a severe tax upon the memory. The manifest and urgent need of reform, which these circumstances create, must be my excuse for presenting in a short note a suggestion likely to require much elaboration. A systematic nomenclature, I need hardly say, can only rest upon a systematic classification, so that the proposals I shall herewith make would have been fitly accompanied by an attempt at producing a classification of the kind. As I have found, however, that much expenditure of time and labour will be necessary to accomplish this task, I have decided upon publishing at once certain proposals with regard to nomenclature, which could be largely applied to classifications at present in use.

From time to time I have received from correspondents suggestions that the method of determining the geological age of the Earth by the rate of solvent denudation of sodium might be open to considerable error if the allowance made in my paper (Trans. R.D.S., ser. ii, vol. vii), for sodium chloride carried from the sea by winds and washed from the atmosphere by rain, was seriously at fault. These suggestions arise from incomplete study of the quantities involved. Had more space been given in my paper to this question, the hasty criticisms I have had to contend with, doubtless, would be less often advanced. The whole matter is capable of the simplest arithmetical statement, and the limit of error arising from this source easily defined. Recently one gentleman has written at considerable length on the matter in the pages of the Chemical News. I have replied to Mr. Ackroyd in that journal. But the definition of the limit of error referred to, and the consideration of some other points raised in the discussion, are more in place in a geological than in a chemical journal. I would therefore seek for space in the Geological Magazine wherein to repeat in part what I have said in the Chemical News, adding some matters more especially suited to geological readers.

Mr. Herbert J. Jessop, who has recently returned from a journey in Eastern Peru, kindly placed in my hands, for examination, some specimens of graptolites which he had obtained on the River Macho, one of the tributaries of the Inambari, near the celebrated mountain Capac Orco, or Monte Bello, in the province of Carabaya, Peru (lat. 13° 40′ S.; long. 70° 10′ W.). The locality is situated on the north-east of the main watershed, and the rivers flow eventually into the Amazon. The difficulties of travelling make it likely that a long time will elapse before other specimens are forthcoming from this locality; it seems desirable, therefore, that some account of these should be published.

In the lower beds remains of a Sirenian are very common, and several more or less complete skulls associated with some portions of the skeleton were found. The skull in most respects resembles that of Halitherium. The snout is strongly deflected and bears a pair of downwardly directed incisor tusks. There are about seven cheek-teeth, resembling in pattern those of Halitherium. The roof of the skull between the temporal fossæ is flat. A cast of the braincase has been made, and in most respects it resembles that described by Owen as the type of Eotherium ægyptiacum, from the Mokattam of Cairo. Since this seems to have come from nearly the same horizon as our specimens, I believe that there is the highest probability that they are referable to this same species, in spite of some differences between the shape of the natural cast described by Owen and that artificially made from one of our specimens.

The paper is divided into two parts, viz.:—

1. Sedimentary Rocks.

2. Igneous and Metamorphic Rocks.

Additional Notes.—These further references and fuller quotations are here given with the view of making the History of the Sarsens, or Sarsen Stones, more complete and more easily available, especially by indicating the chronological succession of observed facts and published opinions.

In his Illustrations of the Botany of the Himalayan Mountains, published in 1839, Royle figures several important fossil plants from the Burdwan Coalfield of India. These are of especial interest, not only as being the first mention of several of the best known fossil types from the Lower Gondwanas of India, but also as among the earliest descriptions of members of the Glossopteris flora.

In this paper the author deals with some of the results obtained in the course of a survey of Eastern Sinai during the season of 1898–99, his remarks being based on a map carefully prepared by his colleague, Mr. H. G. Skill, F.R.G.S., and on his own topographical and geological observations.

In the memoir recently published by the Geological Survey on the Selbornian strata of England, no mention is made of an interesting section in the Gault near Glynde, which was certainly in existence up to 1898, when I last visited the district. The object of the present note is to put this section on record, together with some observations on two chalk quarries, from which I have at various times collected fossils.

There are six specimens of this variety in the Woodwardian Museum, all of which come from the Woolhope Limestone, of Littlehope, and were labelled by Salter. Five of them are more or less perfect head-shields, and the other is a pygidium in a good state of preservation.

A Sea-Breeze is salt-laden in varying degree. On a fine dry day it may contain as much as 22 milligrams of salt per cubic metre of air (Armand Gautier, Bull. Soc. Chim., 1899 [iii], 21, 391–392). This invisible salt is washed out of the atmosphere by rains, and finds its way back to the sea.

In one of his recent visits to the Natural History Museum, Major C. E. Beadnell kindly showed me a fine example of the well-known shell Pleurotoma prisca, which had been obtained some years ago by his son, Mr. Hugh J. L. Beadnell, F.G.S. (now of the Geological Survey of Egypt), when collecting specimens from the Barton Clay (Middle Eocene) in the historical cliffs at Barton, Hampshire, whence, prior to 1766, Gustavus Brander, F.R.S., made his famous collection, some of the specimens of which are still preserved in the British Museum (Natural History).

In the 22nd Report of the Committee appointed to investigate the rate of increase of underground temperature, read this year before the British Association in Glasgow, some remarks previously made by me are animadverted upon; and as the Secretary, Professor Everett, has invited me to discuss the matter with him, I take the opportunity of entering somewhat more fully into the question of conductivity than has hitherto seemed necessary. We read in the Report “… . in view of the fact that the President of Section C last year characterised the variation in the British Isles ‘from 1° in 34 feet to 1° in 92 feet’ as ‘a surprising divergence of extremes from the mean,’ it is well to emphasise the connection between gradient and conductivity. If there is anything like uniformity in the annual escape of heat from the earth at different places, there must necessarily be large differences in geothermic gradients, since the rate of escape is jointly proportional to the gradient and the conductivity.”

There are three specimens of this species in the Woodwardian Museum, viz.: (1) Salter's fine original specimen (a 954) from the Wenlock Shale of Malvern, belonging to the first part of the Fletcher Collection, acquired prior to 1873; (2) a poor specimen probably from the same collection and horizon, locality unknown; and (3) an almost perfect specimen, also from the Wenlock Shale of Malvern, belonging to that part of the Fletcher Collection recently presented by Mrs. Fletcher. This specimen will be designated the Fletcher specimen in distinction to Salter's original specimen. Both these specimens show almost the whole trilobite preserved in excellent condition, and from them the following description has been drawn up.

In the “Annual Report of the Geological Commission” published at Cape Town in 1895, Dr. Corstorphine refers at pp. 16–19 to the extent and features of the Enon Conglomerate, and to the occurrence of fossil Estheriæ in some of its strata. His two assistant geologists, Messrs. A. W. Rogers and E. H. L. Schwartz, in their “Reports on the Southern Districts between Breede River and George” and “On Oudtshoorn,” at pp. 73, 76–79, describe in detail the position and characters of the Enon Conglomerate and its ‘Estheria shale.’

This “remarkable variety of granite” was briefly described by Mr. J. J. Harris Teall, F.E.S., in his “British Petrography” (1888), p. 316, and an interesting account was given in a footnote of the process by which the author was able to identify the topaz found in the rock.

I thought, perhaps, some readers of the Geological Magazine might be interested in a few notes taken during the International Geological Congress excursion to the Massif of Central France and the region of the Causses, and on the chief rocks there, with the best places for finding examples.

Many are the attempts that have been made to discern some law in the occurrence of earthquakes, and to trace the influence of the sun, the moon, or even of the planets as a cause, if partial, of their origin. Many patient investigators have discovered, or thought they have discovered, periods of fluctuating seismic activity, varying in length from semi-diurnal to annual or even longer, but so conflicting have been their conclusions that little weight can be, or has been, attached to the results of their calculations; and one of the most industrious of all these investigators, the Commandante de Montessus de Ballore, has declared his conviction that no periodicity can be detected, and that the causes of earthquakes are purely terrestrial and in no way affected by any celestial body. Yet, in spite of this, the attempts and the calculations go on, and one of the most recent of these is a discussion by Herr M. Becke of some three hundred earthquakes recorded in the region round Karlsbad between 24th October and 25th November, 1897.

So much confusion has existed on the subject of limburgite, that, although it has now been partly dissipated, a record of my own investigations may be of use, at any rate to English petrologists. The rock has been classed by some with the peridotites. From these it is separated by Rosenbusch, who in his latest work places it in a subgroup with the augitites in proximity to the basalts. Zirkel uses limburgite as a synonym for magma-basalt. F. Graeff implies relationship with the nepheline-basalts. Harker's remarks suggest similar conclusions, as do those of Cole, though his opening words are perhaps slightly misleading. All, however, lay so much stress upon the absence of felspar, by giving such definitions as “Limburgite und Augitite sind die felspathfreien Entglieder der Gesteinreihe Trachydolerit, Tephrit,” etc., or “Frei von Feldspar und Felspathoiden ist der Limburgit,” and in some cases by reference to the peridotites, that students may readily overlook the fact that this rock is only free from felspar in the same sense as tachylite or many pitchstones and obsidians.

Last February, while working in the Chemical Laboratory of University College, London, I had occasion to make some sulphanilic acid. This was done in the usual way by heating a mixture of 100 grammes of concentrated sulphuric acid and 30 grammes of aniline to 180°–190° C. in an oil bath for four hours. The flask containing the mixture was left in the oil bath to cool, and on examining it the next day I was surprised to find that the solid mass inside had developed a beautiful spherulitic structure. As I believe this has never been observed before, it may be worth a description.