The causes of the peculiarities of the solar rotation exhibited by the superficial layers of the sun's body must still be considered unknown, notwithstanding recent interesting attempts at explanation. This is no doubt partly due to the difficulties of the hydrodynamical problem placed before the mathematician in an investigation of such complexity as the movements of particles in a rotating fluid subject to energetic convection. But it must also be conceded that the observational data available for a basis of mathematical, or even speculative, research are still so scanty, that for this reason alone we may perhaps not feel surprised at the failure so far of theoretical attempts.

The most mountainous parts of Scotland are situated in its western and north-west districts. From those parts of the country, several chains of mountains branch off, and continue their courses in various directions, and to various extent. The most extended of those chains is that of the Grampians. This chain takes its rise from nearly about the centre of the above alpine district, and continues its course in a direction almost due east, or perhaps a little to the south of that point, until it disappears in the German Ocean, betwixt the towns of Aberdeen and Stonehaven.

Recent investigation of the historical Mont d’Haurs section near Givet yielded numerous trilobites from Middle Devonian carbonate deposits. The trilobite fauna described in the present paper comprises a number of taxa from the basal Givetian, including two new ones: Dechenella givetensis sp. n.; Dechenella calxensis sp. n.; Dechenella ziegleri Struve, 1992; Goldius cf. capitellum (Archinal, 1994); and Nyterops cf. hollandi van Viersen, 2007a. This fauna confirms the previously recognised taxonomic diversity pattern and the Dechenella and Nyterops Association from the middle Middle Devonian in the Ardenne area.

If light, emanating from a fixed source, be reflected to the eye, also fixed, from the surface of a polished cylinder, which cylinder changes its position in some definite manner, the point of reflection moves in some curve or locus whose nature may be made the subject of investigation.

In the present paper I propose to examine that case in which an indefinitely thin cylinder is restricted to pass through a fixed point. The locus of the point of reflection is then a curved surface, For the present I shall still farther restrict the polished line to the plane passing through the vertex, the source of light, and the eye ; the locus being then a plane curve.

Let then a fine polished straight line, extended indefinitely both ways, turn on the vertex O, while light emanating from the source A is reflected to the eye at B; it is required to investigate the locus of the point C at which the reflection takes place.

The reflection is only possible while the polished line passes outside of the angle AOB. When the wire lies along AO, the point of reflection is at A ; when along OB, at B; and when it is equally inclined, outwards, to OA and OB, the reflection occurs at O, wherefore the curve must pass through the three points O, A, and B.

Towards the end of May of this year I made my third visit to the Rigi Kulm, for the purpose of continuing my observations on the amount of dust in the atmosphere and other meteorological phenomena. It was with a feeling of no little satisfaction that I found myself at that elevated situation during broken weather, and under conditions very different from any previously experienced by me. On this occasion I had come in the hope of finding opportunities for making some observations on the conditions existing in clouds, in addition to the usual dust observations, and had brought with me the small instrument for observing the water particles in a fog, described in a previous communication to this Society. As the weather continued to be variable during the week of my visit, I was fortunate enough to succeed in making a number of interesting observations on the water particles in clouds, and also of comparing the conditions in clouds at this elevated situation with those previously observed in fogs at a low level.

Before giving the results of my observations on the water particles, it may be desirable to make a few remarks on the solid or dust particles. When making the ordinary dust observations this year, it was frequently noticed that, when surrounded by clouds, the number of particles varied greatly at short intervals of time.

Recent water-undersaturated phase equilibrium data on the subsystems of the granite-H2O system have provided important new constraints on the topology of the cotectic surfaces and hence on the compositional evolution of felsic magmas. The effect of water on phase relations can be deduced from a comparison of anhydrous and H2O-saturated data or from data obtained in the presence of a CO2-bearing fluid. However, although new experimental evidence indicates that the silica enrichment of evolving H2O-undersaturated, H2O-unbuffered melts during the co-precipitation of quartz and feldspar is as previously thought for orthoclase-rich compositions, it suggests that such a trend is considerably less for Ab-rich compositions. For water-poor trachytic melts, the newly recognised strong destabilisation of the sanidine melt component relative to the anorthite melt component with increasing water content indicates that the co-precipitation of two feldspars will result in saturation of the melt with ternary alkali feldspar at an earlier stage (i.e. higher melt anorthite content) than previously thought. This, in turn, implies that the melt differentiation path will have a greater component of anorthite depletion during the equilibrium co-precipitation of ternary feldspars and that the melt will remain in the peritectic region of the two feldspar plus liquid surface over a greater interval of crystallisation, thereby enhancing the possibility that the resoption of plagioclase during the early stages of equilibrium with alkali feldspar may go to completion. Comparison of CO2-free and CO2-bearing haplogranitic phase equilibrium data suggests that CO2 may be playing an independent part in the modification of phase equilibria and may induce a significant destabilisation of the orthoclase melt component.

The geological and tectonic background of the Sabalan area in NW Iran and its present-day surface processes make it ideal for examining the effects of tectonic processes in shaping the Earth's crust. As a result of the intense distribution of pre-Quaternary and Quaternary structures (e.g., faults, joints and folds), most of the drainage basins in the southern and central parts of the study area have developed under tectonic-dominated conditions, whereas the effects of erosional processes are greater in the north and east. An evaluation of the geomorphic indices using the index of active tectonics (IAT) and analytical hierarchy process (AHP) methods shows that the AHP results are more reliable than the IAT results and are coherent with the geological and structural conditions of the study area. The geomorphic results are highly consistent with the intensity and distribution of fractures. The majority of fractures have developed in a NW–SE direction, indicating antithetic R′ Riedel fractures to the main NE-SW-trending faults. However, a significant number of the fractures in the study area are NNE–SSW- and NE–SW-oriented R and P fractures and NNW–SSE-oriented tension fractures. Palaeostress analysis of the fault data shows at least two faulting events in the pre-Quaternary and Quaternary, respectively. The pre-Quaternary NNW–SSE-striking dextral strike-slip faults experienced post-Eocene 25–30° clockwise rotation and re-activated as NE–SW-striking sinistral faults during the Quaternary. Although seismic activity is currently low, the consistency of our results with the regional stress data show that the study area is still tectonically active.

The experiments to which I shall refer were carried out in the physical laboratory of the University during the late summer session. I was ably assisted in conducting the experiments by three students of the laboratory,—Messrs H. A. Salvesen, G. M. Connor, and D. E. Stewart. The method which was used of measuring the difference of potential required to produce a disruptive discharge of electricity under given conditions, is that described in a paper communicated to the Royal Society of Edinburgh in 1876 in the names of Mr J. A. Paton, M. A., and myself, and was suggested to me by Professor Tait as a means of attacking the experimental problems mentioned below.

The above sketch which I took of the apparatus in situ may facilitate tha description of the method. The receiver of an air-pump, having a rod capable of being moved air-tight up and down through the neck, was attached to one of the conductors of a Holtz machine in such a manner that the conductor of the machine and the rod formed one conducting system. Projecting from the bottom of the receiver was a short metallic rod, forming one conductor with the metallic parts of the air-pump, and by means of a chain with the uninsulated conductor of the Holtz machine. Brass balls and discs of various sizes were made to order, capable of being screwed on to the ends of the rods. On the table, and at a distance of about six feet from the receiver, was a stand supporting two insulated brass balls, the one fixed, the other having one degree of freedom, viz., of moving in a straight line in the plane of the table. The fixed insulated ball A was made one conductor with the insulated conductor of the Holtz and the rod of the receiver, by means of a copper wire insulated with gutta percha, having one end stuck firmly into a hole in the collar of the receiver, and having the other fitted in between the glass stem and the hollow in the ball, by which it fitted on to the stem tightly. A thin wire similarly fitted in between the ball B and its insulating stem connected the ball with the insulated half ring of a divided ring reflecting electrometer.

In the beginning of July last, I obtained, from the Frith of Forth, a species of bream, which has not been mentioned by naturalists as inhabiting the British seas. A few days after, I procured, from the same quarter, a second specimen of the same species, each exhibiting a conspicuous dark violet-coloured spot at the base of the upper part of the pectoral fins. (See Plate VI.)

On consulting the continental works on Ichthyology, I find this bream to agree best with the description Baron Cuvier has given of the Pagellus acarne, an inhabitant of the Mediterranean; but, as no figure of the fish accompanies his description, the discrimination of the species is rendered somewhat uncertain.

Before commencing the discussion of the subject, it is necessary to make some definitions, with a view to avoiding the confusion which extensively prevails, from the neglect of the all-important definition of terms. I might be even more exact than I shall be, and excuse myself from adopting such a seeming improvement, on the ground that further refinement of definition would itself cause confusion in the present stage of advancement of our knowledge.

Absolute sterility, I shall hold to mean the condition of a woman who, under ordinary favourable cirumstances for breeding, produces no living or dead child, nor any kind of abortion.

Sterility, I shall hold to mean the condition of a woman who, under ordinary favourable circumstances for breeding, adds not even one to the population, or produces no living and viable child.

Relative sterility, I shall hold to mean the condition of a woman who, while she may or may not be absolutely sterile, while she may or may not be sterile, is, under ordinary favourable circumstances for breeding, sterile in relation to the circumstance of time; or, in other words, in relation to her age, and the duration of her married life.

A few years ago the late Sir C. Wyville Thomson gave me for examination some specimens of Ascidians which had been obtained during the cruises of the “Porcupine” and “Lightning,” and last summer I received from Mr John Murray the remainder of the Ascidiæ Simplices and two species of the Ascidiæ Compositæ from the same deep-sea dredging expeditions. Some additional specimens of the “Porcupine” Ascidiæ Compositæ have been placed in my hands during the last few days (January 1, 1884). The present paper contains a detailed account of the Simple Ascidians alone; the Compound forms will be worked up along with the “Challenger” Ascidiæ Compositæ, and will be described and figured in the second part of my Report upon the Tunicata of the “Challenger” Expedition. It may, however, be useful to state here that the “Porcupine” Compound Ascidians include:—

I some time ago had the honour to present to the Royal Society, a specimen of a very singular fossil which had been found in the freestone quarry of Craigleith, near this city. It presented the appearance so commonly met with in the sandstone of the coal-formation,—an impression of what has always been considered as the bark of a vegetable connected with the Palm-tribe; but it differed from any thing I had ever before seen of the kind, by having circular marks ranged in a line along the surface, being apparently the impressions of flowers or fruit. As neither of these grow directly from the stem of any plant now known, except among the Cactus genus, this impression might have been referred to it, had not the regularity of distance between these supposed flowers, pointed out the improbability; and it consequently must be referred to some one, the prototype of which is no longer known.

The size of the specimen, of which the annexed engraving is a very exact representation, is twenty-one inches in length, and about fourteen broad; the widest part of the impression measures four inches, and the diameter of the circles a little more than three.

No quality is more inconsistent with the character of a stone than flexibility. A flexible stone, therefore, presents an idea which naturally strikes us with surprise. For though among mineral bodies, we find flexible substances of the stony kind, such as mica, mountain leather, and amianthus, these minerals owe their flexibility, either to their thinness, or to the fibrous structure of their parts. Therefore, when a stone of any considerable thickness is said to have flexibility, we are led to think that here is something very extraordinary; and we wish to know upon what depends that quality, nowise proper to a stone.

Sir George Clerk-Maxwell of Pennycuik, Baronet, one of the Presidents of the Physical Class of this Society, was born at Edinburgh, on the last day of October 1715. He was the fourth son of Sir John Clerk of Pennycuik, one of the Barons of Exchequer in Scotland: His mother was a daughter of Sir James Inglis of Cramond.

His more early studies were carried on at the University of Edinburgh, under the eye of his father, who was himself a man of letters, and from whom he appears very early to have caught a strong taste for Natural History, Antiquities and the Theory of Commerce, particularly in so far as these branches of knowledge related to his own country. He afterwards went to Leyden, where he finished his studies under the immediate inspection of the celebrated Boerhaave, who had been the friend of his father; and, before his return home, he visited several parts of France and Germany.