After the death of the late Professor Tait in 1901, I was asked by the Council of the Royal Society of Edinburgh to carry to completion the task which Professor Tait had undertaken of presenting Professor Andrews' epoch-making work in such a form as to make possible the estimation of the true pressures.

At the meeting of February 20, 1899, Professor Tait communicated the first instalment of a paper on “The Experimental Bases of Professor Andrews' Paper on the Continuity of the Gaseous and Liquid States of Matter (Phil. Trans. 1869).”

This second paper is a discussion of the surface displacements associated with plane elastic waves reflected from the boundary of the elastic solid through which they are being propagated. In my first paper on Seismic Radiations (Proc. Roy. Soc. Edin., vol. xxviii. pp. 217–230, 1908) my aim was to find a simple distribution of density and elasticity in terms of which the transmission of seismic disturbances could be described.

By experimental methods a close similarity has been shown to exist between certain simple stress systems and the corresponding systems of hydrodynamic flow. How nearly exact this similarity is, and how widely the application of the principle may be extended, are points which remain to be determined.

In a simply loaded bar there are secondary stresses which vary with the shape of the bar; the existence of these secondary stresses explains some apparent anomalies in the character of the lines of deformation.

The object of the present series of experiments is to find the variation of the illuminating power of symmetrical groups of pin-hole burners with the distance of adjacent burners.

The burners were fitted so as to slide on a frame composed of two pieces of a metre-rod fastened together to form a cross, as shown in figs. 1 and 2. The stems of the burners were circular in section and cylindrical in bore, the external and internal diameters being 8 mm. and less than 1 mm. respectively. Their bases were bevelled in such a manner that the burners could be fixed so close as to touch each other; thus their centres could be placed at any distance from the centre of the cross from 4 mm. to 10 cm. The standard of illumination with which they were compared was a similar pin-hole burner.

Our purpose was, by a systematic study of the solubilities concerned, to ascertain whether any hydrates of orthophosphoric acid, other than a semi-hydrate, 2H3PO4,H2O (Joly's hydrate), exist. The solubilities of phosphoric acid and Joly's hydrate at various temperatures had not previously been measured. Crystalline, anhydrous phosphoric acid and Joly's hydrate were prepared in pure form. The solid was stirred in a thermostat with water until equilibrium was reached at each temperature, and the concentration of the solution was determined. The diagram (fig. 1) shows the results. AB is the curve of solubilities of Joly's hydrate from −16° to 29·35°, its melting point. BC contains the melting points of Joly's hydrate, depressed by phosphoric acid.

This contribution is a continuation of a former paper on the same subject, references to which in this paper will, for the sake of brevity, be referred to as ante, p.…, or ante, fig.… The present pages deal especially with the following districts of Scotland:—

1. North-west Kirkcudbrightshire.

2. South-east Kirkcudbrightshire.

3. Wigtownshire.

4. Fife and Kinross.

The chemistry of this not the least interesting of deep-sea deposits, though it has received attention from several investigators in the past, still presents some uncertainties as regards both the analytical composition of the material and its chemical nature. It has therefore been suggested by Sir John Murray, to whom directly or indirectly all our knowledge of Red Clay is due, that the subject might with advantage be reopened from the chemical standpoint. The results of this revision, which was carried out in the Challenger Laboratory at Edinburgh, are set forth and discussed in the ensuing pages.

The kindness of Professor Cunningham has enabled me to carry out the dissection of a gibbon in his possession. The dissection was performed in 1905, in the Anatomical Department of the University of Edinburgh. The following paper is a description of the short muscles of the hand of the animal, to which is added a consideration of the primitive position and function of the short muscles of the human hand.

In a recent note to the Royal Society of Edinburgh, Dr Dawson Turner remarks on a peculiarity observed by him in the behaviour of an inductioncoil spark-gap when a piece of mica, glass, sulphur, ebonite, etc., is placed between the terminals, near or against the + one. The surprising variety of the phenomena exhibited on the interposition of a solid dielectric plate between the two poles of such a coil (or between the poles of an influence machine) may make, in view of Dr Turner's note, the following observations of some interest. The observations in question were made during the course of an inquiry into the causes of the Lullin effect (according to which a thin dielectric plate interposed between two sparking terminals not opposite to one another is, as a general rule, perforated at the negative pole), and the apparatus employed consisted essentially of the details shown in fig. i., viz. of a motor-driven influence machine whose terminals were connected through a battery of Leyden jars in cascade to a specially designed spark-gap which allowed of any three-dimensional motion of the electrodes being accurately measured, and of any desired type or form of electrode (spherical, conical, disc type, etc.) being inserted at will.

The apparent prodigality with which Nature provides for the reproduction of plants and animals has a marked exception in the case of sterile organisms, often produced on a large scale, in which every function except that of propagation may be carried on in a quite perfect manner. The cases of the sterilisation of an organism are best seen in insects, but I wish at present to consider its occurrence high up in the animal kingdom in the well-known case of the Free-Martin, an apparent sterile cow born co-twin with a potent bull.

§ 1. In a former paper “On Group-Velocity and on the Propagation of Waves in a Dispersive Medium” (Proc. R.S.E., xxix. pp. 445–470, 1909), it was shown that group-velocity, or the principle of “stationary phase,” provides us with a satisfactory explanation of the modus operandi of dispersion; and the principle was applied to obtain an expression for the effect of a single impulse confined to the neighbourhood of a point of the medium. The present paper is intended to fulfil a promise given in § 29 of that paper, to show that by means of this principle we can arrive at the general features of the wave-system in a dispersive medium resulting from any limited initial disturbance.

Kohlrausch and others have recently published investigations which show that the electrolytic conductivity of dilute solutions of inorganic salts may be determined with a maximum error of two or three in ten thousand.

Hitherto such accuracy has not been attained with highly conducting concentrated solutions. With such solutions different difficulties are encountered from those met with in dilute solutions. Temperature variations originating outside the cell, the heating effect of the current within the cell, and polarisation are sources of error which are particularly troublesome in the case of highly conducting solutions.

Notwithstanding the generalisations made by Jacobi and Cauchy, the special case with which the whole theory originated continued from time to time to attract attention. In 1843 William Thomson, afterwards known as Lord Kelvin, published under the signature “T.” in the Cambridge Math. Journ., iii. pp. 247–248, a short note in which he proved the detached theorem that if l1, m1, n1, l2, … be nine quantitiessuch that

then it follows that

This led to a short paper by A. Göpel in the Archiv d. Math. u. Phys., iv. (1843) pp. 244–246.

In a work published in 1846, Professor Owen figured two upper molars of a small member of the Equidæ family which lived in the south of England along with the mammoth. A study of these and other molars led Owen to conclude that the small equine which lived in England in prehistoric times was either an ass or a zebra. Assuming that the small Oreston fossil equine had “callosities on the fore legs only, the tail furnished with a terminal brush, and a longitudinal dorsal line,” Owen gave it the name Asinus fossilis. In support of the view that a “wild ass or quagga” as well as a wild horse and a wild boar entered “into the series of British Pliocene hoofed mammalia,” Owen mentions that he had seen a fossil second phalanx or pastern bone of a small species of Equus about the size of the zebra from the Pliocene crag at Thorpe, and that Dr Mantell had described teeth and bones of “a small species about the size of a Shetland pony“ from the super-cretaceous drift deposit at Brighton—the deposit which, owing to the abundance of mammoth bones, is known as the “Elephant Bed.”

Following on the current observations made during 1908 in Loch Ness by the author and Mr W. Watson, a few observations were made in Loch Garry (Ness basin) during August and September 1909. Mr Macdonald, Fort Augustus, again assisted in the work. The Loch Ness observations showed that the currents in the loch were very confused, but certain general conclusions were drawn; e.g. (1) that when a lake has become stratified and the temperature discontinuity has appeared, the return current is nearly always found above the discontinuity; (2) that towards the windward end of the loch the return current may take place close to the surface; (3) that slow-currents are to be found below the discontinuity, and with the same direction as the surface current. All these conclusions are borne out by the Loch Garry observations, and some additional information has been obtained.

Amongst the unnamed Alcyonaria in the collection of the Royal Scottish Museum, Edinburgh, is a beautiful colony belonging to the genus Cactogorgia, which Mr Eagle Clarke has kindly handed me for identification and description.

In 1907 (Trans. Roy. Soc. Edin.) I established the genus Cactogorgia for several small colonies from the Indian Ocean, and referred these to three separate species, viz. celosioides, alciformis, and expansa. Thomson and M'Kinnon, in Trans. Linn. Soc. (Zool.), 1909, have described another species from the Seychelles under the name of Cactogorgia lampas, and the present colony must also be referred to a new species. This we propose to name Cactogorgia agariciformis, n. sp., on account of its very definite mushroom-shape.

Concerning the development of the ganglia and plexuses in the intestine, various theories have from time to time been formulated. The older writers, among whom were Remak (1, 2), Götte (5), Balfour and Foster (6), assumed that they had a mesoblastic origin, were formed in situ, and became joined on to the main sympathetic chain at a later date.

Later, an ectodermic origin was generally recognised as belonging to the central nervous system, but writers were not agreed as to the origin of the sympathetic. A few, among whom were His (4), Birdsall and Schenk (8), maintained that its origin was, like the central nervous system, ectodermic, but many held the older view that it was a mesoblastic structure.

According to Percy's definition, “clays are termed fireclays or refractory clays when they resist exposure to a high temperature without melting or becoming in a sensible degree soft and pasty.” The refractoriness of fireclay is due to its low proportions of fluxes. The best known British fireclays occur beneath the coal seams of the coal measures, and are therefore known as “under-clays” or “seat-clays.” The explanation of their paucity of fluxes usually offered is that the alkalies have been withdrawn as food by the vegetation which formed the coal. Thus Professor Tarr remarks that fireclays “are particularly abundant in the Carboniferous rocks associated with coal beds, the plants having been instrumental in the withdrawal of the alkalies.” This view has been widely accepted, and the death of the successive coal forests has been attributed to the exhaustion of the plant foods in the underlying soils. Caution is, however, necessary in the application of this theory; for plants can only withdraw soluble alkalies from the soil, and the alkalies are usually present in the form of silicates, which decompose slowly. Hence the total removal of alkalies from a soil by vegetation would be a very lengthy process. Moreover, alkalies are not the only, or indeed the most common of fluxes, for iron is usually the most potent. Further, some good fireclays are not associated with coal seams, while well-washed river muds may be poorer in alkali than an underclay, the alkalies having been washed out of the material. Thus the river muds from the Rhine near Bonn, analysed by Bischoff, contain only ·89 per cent. of potash and ·39 per cent. of soda; or after deducting the water and organic material the percentages of potash and soda are 1·02 and 0·45 respectively. Another analysis by Bischoff of river mud from the Rhine collected above Lake Constance contained potash ·55 per cent. and soda ·54 per cent., or after deducting the water and carbonates the percentage of these two constituents only rose to ·91 per cent. of potash and ·90 per cent. of soda.

The absence of china clay from Scotland has been used as a weighty argument in favour of the pneumatolytic or deep-seated origin of the great china clay masses of Cornwall and Devonshire, of southern Sweden, and of some of those in Germany. Kaolin, which is often regarded—I think correctly—as a synonym of china clay, and kaolinite, have, however, been occasionally recorded as occurring in Scotland. A reported occurrence at Troon may be easily dismissed. Thus it is only recorded doubtfully, with the remark that its composition has not been determined, by J. Sommerville and G. R. Thompson, while John Smith describes it as a bed of finegrained volcanic dust deposited in water. Kaolinite has been recorded by Heddle from several Scottish localities; thus it is found in minute crystals in Shetland, and in a vein at the head of Glen Capel at Abington, Lanarkshire.

The chemical composition of submarine glauconite is of considerable interest in view of the fact that glauconite is the only silicate which is synthesized at the bottom of the sea, and apparently nowhere else. Numerous analyses of this mineral have been published from time to time, but the results are far from uniform, because the material almost always—certainly in most of the older analyses—was anything but pure. The analysis which inspires most confidence on this score is one which was recently carried out in the Challenger laboratory by Collet and Lee on a purified granular glauconite dredged off the Californian coast by U.S.S. Tuscarora (1879).