The two phenomena, the subjects of the present paper, have found a place in the current popular scientific literature of the day, and exercise a considerable influence on the opinions of the casual votaries of science, and even of some of those who are its regular cultivators. For that reason I shall go more into detail than otherwise would have been needed.

In the beginning of the session Professor Tait read a paper on Mirage, and exhibited to the Royal Society of Edinburgh an enlarged representation of an aërial phenomenon described by Professor Vince. The Professor of Mathematics inquired of me my opinion as to the explanation offered; and I now reply to Mr. Chrystal's inquiry indirectly, not by discussing in any way Mr. Tait's analysis, but by examining the major proposition, the reality of the phenomenon.

The dyspepsia was, as far as I know, of a very ordinary kind. It began with loss of appetite, discomfort after meals, and general sense of weakness and uselessness. Then came a crisis. Waking in the middle of the night with pain and nausea, an hour or two of this, thorough evacuation of the stomach, great discomfort next day, and then no symptom of any thing wrong as long as I adhered to the diet which experience soon led me to, viz., very simple food and very little of it. To this I adhered for about four weeks. Now and then, perhaps three times altogether, feeling quite well, I ventured to eat like other people, and was at once taught by abdominal pain and diarrhœa, that I must still consider myself an invalid, or at best a convalescent.

The well-known northward attenuation of the massive Carboniferous Limestone of Lancashire and Yorkshire, and the gradual replacement of its thick calcareous groups by sandstones, shales, and seams of coal, with interstratifications of marine limestone, can be advantageously studied in the southern counties of Scotland. In these districts a characteristic and recognisable base for the Carboniferous system is presented by the deep red Sandstones and marles of the Upper Old Red Sandstone, which pass up conformably into that system, but rest with a violent unconformability upon every formation older than themselves, including even the Lower Old Red Sandstone of Berwickshire and the Cheviot Hills.

Through the kindness of Professor Geikie, Director-General of the Geological Survey of Great Britain, I have had the pleasure of examining the fossil plants collected by the Scottish Geological Survey in Eskdale and Liddesdale.

The collection contains about four hundred and fifty specimens, a number of which, however, were too imperfect for further identification than that of the genus.

Eight of the plants I believe to be new species, and a few of the others, as far as I am aware, are now recorded for the first time as occurring in Scottish rocks.

Some time since, specimens of a peculiar-looking rock, found at Fintry, in the Campsie district, were put into our hands for analysis. The specimens were of a light chocolate-brown colour, and apparently homogeneous. They were somewhat harder than ordinary limestone, had a waxy lustre, and broke with a sharp-edged splintery fracture, translucent upon the thin edges. With hydrochloric acid they effervesced slowly, at the same time gelatinising. The specimens were weathered white to a considerable depth.

(a) The oblate ellipsoid of revolution is proved in Thomson and Tait's Natural Philosophy (first edition, § 776, and the Table of § 772) to be stable, if the condition of being an ellipsoid of revolution be imposed. It is obviously not stable for very great eccentricities without this double condition of being both a figure of revolution and ellipsoidal.

(b) If the condition of being a figure of revolution is imposed, without the condition of being an ellipsoid, there is, for large enough moment of momentum, an annular figure of equilibrium which is stable, and an ellipsoidal figure which is unstable. It is probable, that for moment of momentum greater than one definite limit and less than another, there is just one annular figure of equilibrium, consisting of a single ring.

Before leaving for India, in the end of 1876, it occurred to me that, as almost nothing seemed to be known about atmospheric electricity in the tropics, it would be well if I could take with me the apparatus necessary for making observations on it. I accordingly communicated with Sir William Thomson, who kindly obtained for me a grant from the British Association, for a portable electrometer. This instrument I took with me, and the following are the results of the observations made with it.

The two diseases have been long known in Scotland, and are the cause of serious loss to stock owners. Well-informed breeders have estimated the loss at not less than half a million sterling annually.

They resemble each other in being peculiar to certain districts, and in prevailing at certain seasons of the year. Louping-ill is most frequently met with in the southern and western counties, and chiefly affects sheep feeding on rough hill pastures. It occurs during May and early in June, and is most fatal amongst lambs, but old sheep, cattle, pigs, and even poultry are liable to it. A few sporadic cases are met with in October, especially in the Western Highlands, where it is known under the name of trembling. Braxy, known also as inflammation and sickness, is more general in its occurrence, and affects high and low pastures alike. It is more or less prevalent from October till February, and attacks sheep in good condition.

In the microphone transmitter, as usually employed in circuit with a battery and a Bell telephone, we have essentially two pieces of carbon resting lightly against each other, through which the current passes. That the instrument may work effectively two things are requisite,—first, that the carbons be always in contact, or at least sufficiently near for the current to pass between them; and, secondly, that they be not pressed together so tightly as to prevent any motion of the one relatively to the other. This state of things is sufficiently well described by the term “loose contact,” first used, I believe, by Professor Stokes.

These experiments were begun in January last at the request of Professor Tait, and have been carried on since then in his laboratory. The subject suggested itself to Professor Tait during his experiments on the effects of great pressures on thermometers carried out for the “Challenger” Expedition Commission, and it was indeed by part of the apparatus purchased by him for this purpose that the experiments were made. The method adopted was of an indirect nature, and consisted in determining first the change of temperature produced by a sudden change of pressure to which the water was subjected.

This earthworm, which is an inhabitant of Ceylon, is 28 inches in length, and consists of about 260 segments. The setæ, instead of being arranged in continuous lines round the body as in Perichœta, fail for a short space both dorsally and ventrally. This peculiarity serves to distinguish the genus Pleurochœta from other Oligochœta. The intestine is provided with two sets of specialised glands; the anterior, occupying from segments twenty-two to forty-four, consists of a double series of deeply excavated dorsal pouches on the wall of the intestine, provided with a large development of glandular epithelium; the posterior glands are solid and kidney-shaped, about the size of a grain of wheat. They lie on the dorsal surface of intestine, occupying from the eighty-fifth to the one hundred and first segments; in all, fifteen pairs. They open into intestine by ducts.

Since the discovery, by His Grace the Duke of Argyll, of the “Leaf-bed” at Ardtun, in Mull, there has not, so far as I am aware, been another found throughout the whole of that extent of land and shore, where we might hope for such a discovery, among the Inner Hebrides.

It was my good fortune to light upon one last summer. While lying in the harbour of the island of Canna, during a boulder and mineral hunt, I heard that fuller's earth had been found at the south-western end of the island. Upon being shown samples of this, I noticed among them fissile schists very similar to those of Ardtun. In proceeding, therefore, round the western cliff-girt coast of the island, to visit the fuller's earth locality, we landed at every accessible point under the great line of precipice, and at one, situated almost at the north-west corner, and immediately under the loftiest point,—more than 730 feet in height,—we found a leaf-bed. There is here a cliff foot, running for some little distance along the shore; this is strewed with numberless masses of rock which have fallen from the cliff, and which fragments give shelter to a colony of auks and puffins.

In a letter to Professor Tait, dated Mentone, 14th April 1882, Mr. Aitken says :—

Since coming here this time, I have tested the sea with the polariscope and with the spectroscope. With an instrument by Hoffman, which gives coloured bands with polarized light, I have been able to detect small, but decided indications of polarization in the light internally reflected by the water, the surface reflection being, of course, cut off when the observation was made. At present I think the polarization is due to regular reflection from the polished surfaces of some of the particles, which are seen to glance brightly in concentrated sunlight.

I have also detected an absorption band in the green of the spectrum of the light internally reflected by the Mediterranean water. This band is much more distinct in water where there are but few reflecting particles, and the light undergoes a great amount of selective absorption.

The region known as the Faroe Channel is that portion of the Atlantic Ocean to the north of the mainland of Scotland, which is bounded on the N.W. by the Faroe Islands, with their south-west-ward extending fishing-banks, and on the S.E. and S. by the Shetland and Orkney Islands, the shores of Caithness and Sutherland, and the Hebrides.

The Faroe Islands are composed of basaltic rocks, while the north of Scotland, and the Scottish Islands, are chiefly made up of Laurentian gneiss, Silurian, and Devonian rocks.

The eclipse of the 31st December 1880 was not seen here, and thus we lost the opportunity of comparing the computed with the observed times.

In the daily papers at that time expression was given to a feeling of dissatisfaction that any computation should have been added to that recorded in the Nautical Almanac. And therefore, while laying before the Society the results at which I have arrived in regard to the coming eclipse, it may be proper for me to explain how such an investigation comes to be needed.