The author commences by adverting to a very generally recognised geological difficulty—viz., that of accounting for the disappearance of the mineral from the carbonaceous matter in the processes which have resulted in the formation of coal-beds as we now find them. Coal-beds have undoubtedly their origin from decaying vegetable matter; and the deposition is unquestionably traceable to at least three different sources—viz., the carrying down by rivers of drift wood, and its deposition in deltas and estuaries at their mouths; the accumulations of dead forest trees, &c., falling for successive generations where they had grown; and the growth of peat. But in all of the three methods it is clear that the vegetable matter must have been mixed up to a very large extent with earthy matter, which earthy matter has since disappeared, so as to leave carbonaceous deposits in a comparative state of purity. The explanation of this disappearance has hitherto completely baffled geological ingenuity, and the author, in offering the present solution of the enigma, ventures to hope that he has successfully grappled with the difficulty.

In the course of an examination of the harbours and river mouths of India, which I have recently been making for the Government of that country, instructions were sent me to examine the backwater communication of the Malabar coast, with special reference to the possibility of taking advantage of the anchorage at such localities as Narrakal and Allippey, and opening out communications between them and the backwaters. As these anchorages are so remarkable, and the phenomena connected with them are probably known to but few members of this Society, and the places themselves perhaps never visited by any member present, I have thought a short account of these mud harbours of refuge would be of some interest.

Excepting the months of January and July—the months of extreme temperatures for the larger portions of the globe—there is no month the meteorology of which is so peculiar, and a careful investigation of which is so likely to lead to striking and important results, as the month of May. The peculiarity of the meteorology of the month of May is, that it is the month of the year during which the most rapid rise of temperature takes place over the greater parter part of the northern hemisphere, and the most rapid fall over the greater part of the southern hemisphere; and since that rapid rise and equally rapid fall takes place at very different rates, according to the peculiar distribution of land and water in each region, the inquiry is calculated to bring out in strong relief some of the more prominent causes which influence climate, and some of the more striking results of those causes.

Naturalists have recorded a few instances of the capture of the Greenland shark in the British seas. Dr Fleming states that one was caught in 1803 in the Pentland Firth, and that one was found dead at Buna Firth, Unst, in 1824. Mr Yarrell refers to a specimen caught on the coast of Durham in 1840, which has been preserved in the Durham University Museum. In May 1859, a specimen about ten feet long was caught in the Firth of Forth, near Inchkeith, the stuffed skin of which is preserved in the Edinburgh Museum of Science and Art. In 1862 a specimen was caught on the Dogger Bank, and brought into Leith. A brief description of its externarcharacter was read by Mr W. S. Young to the Royal Physical Society of Edinburgh.

The author gave an account of the mode in which he had treated the Strain-Function in an elementary Treatise on Quaternions, soon to be published, mainly from the pen of Professor Kelland.

The coefficients of the cubic in φ are determined easily from the condition that homogeneous strain alters the volume of every part of a body in the same ratio.

The subject of the following communication is a phenomenon unexpected and peculiar; it presents analogies to the phenomena of magnetism and electricity, in so much as it is an exhibition of repulsion; but it is distinguished from these by the absence of attraction, or what is called polarity. So far as I am aware, it is the only known example of repulsion exhibited independently of magnetic or electric excitement, and seems to open up an entirely new field for physical research. On these accounts I was exceedingly desirous to have it brought without delay to the notice of scientific men, and I have to thank our Secretary for-giving me the present opportunity, although at the inconvenience to him of it having to accompany a long and interesting paper on another subject.

The fishes now exhibited were brought by the Rev. Alexander Robb; D.D., from Old Calabar; West Africa. They were taken in the fresh water of the great Old Calabar River, near Ikorofiong, about a hundred miles or so, by the windings of the river, from the bar near its mouth. The Rev. Dr Robb resides at Ikorofiong, which is one of the stations of the Calabar mission of the United Presbyterian Church.

In the note on the density of the solutions prepared for the purpose of determining their electrical conductivity, it is shown that the ratio of the weight of salt dissolved in unit weight of water to the excess of the density of the solution thus formed over that of water (unity), is not constant, but increases, with greater or less rapidity, from the more dilute to the more dense. The work of previous experimenters on the electrical resistance of liquids is then reviewed at some length. Their chief difficulty has always been the electrolytic polarisation of electrodes.

The following are a modification of some experiments conducted in the summer of 1871, and communicated to the Society on the 15th of January 1872. These consisted in heating a magnet uniformly throughout, and then noting the change in magnetic strength. Those conducted this winter consisted in heating one pole of a magnet, while the other was kept at a temperature as nearly constant as possible, and then noting the change of magnetic strength in both poles. The arrangement adopted was the same in both series of experiments, only being double in the latter. It consisted in having a magnet set magnetically east and west, each end of which passed through a cork fitted into a hole made in the side of a copper pot, one of which was filled with oil and heated by means of a brass Bunsen, while the other was filled with water at the temperature of the air of the room. The temperatures of both ends of the magnet could thus be ascertained by means of mercurial thermometers.

The authors of this communication have more especially directed their attention to the problem of the specific effect produced on the retina and optic nerve by the action of light. Numerous hypotheses have been made from time to time by physicists and physiologists; but up to the present date, our knowledge of the subject is without any experimental foundation. For example, Newton, Melloni, and Seebeck, stated that the action of light on the retina consisted of a communication of mere vibrations; Young conjectured that it was a minute intermittent motion of some portion of the optic nerve; Du Bois-Reymond attributed it to an electrical effect; Draper supposed that it depended on a heating effect of the choroid; and Mosier compared it to the action of light on a sensitive photographic plate.

The late Mr H. T. M. Witham read in 1830 to this Society, and published three years afterwards in greater extension, an inquiry of much interest respecting two fossil trees found in Craigleith Quarry, a mile and a half from the north-west outskirts of Edinburgh. The general points of this inquiry are, that trees of very great size lie, completely fossilised, in the very compact sandstone of the quarry, at a great depth below the rock surface, slightly inclined to the-dip of the strata, with their structure so finely preserved in the fossilising material as to be beautifully shown before the microscope, and recognised as that of the Pinaceous Family, and of the section to which belongs the existing Araucaria. These trees have been generally known to fossile botanists by the name of Araucarioxylon Withami. An opportunity having occurred this year of confirming and extending the inquiries of Witham, it has been thought right to take advantage of it, again through the medium of the Royal Society.

The rapid propagation of Ipecacuan in India is an object of importance, and as such has occupied the attention of the Indian Government. The Edinburgh Botanic Garden has contributed largely to the stock of Ipecacuan plants now in cultivation in India. The plan of sending cuttings of the roots or rather rhizomes enveloped in moss has been very successful. We have been able in 1873 to send these cuttings in small boxes through the post. Dr Henderson, the present interim Director of the Botanic Garden at Calcutta, reports most favourably of this plan. He carried out to Calcutta in 1872 small boxes 8 inches by 2, containing germinating rhizomes of Ipecacuan, and roots of Jalap. These are now thriving under his charge. This mode of transmission will save much trouble and anxiety, and will insure an easy and rapid propagation of the plants. We may expect thus to secure for India a large supply of this invaluable remedy for dysentery.

Since the date of the first communication, we have endeavoured to obtain quantitative results involving time as a variable element in the case of the action of light on the retina and optic nerve, We have therefore found it necessary to construct a true graphical representation of the variations of the electro-motive force occasioned by the impact and cessation of light. It is clear that to register minute galvanometrical alterations, the only plan that could be employed would be to photograph on a sensitive surface, covering a cylinder rapidly revolving on a horizontal axis, the alteration of position of the spot of light reflected from the mirror, just as continuous magnetic observations are registered.

The opportunity of an experiment on a comparatively large scale, and under conditions of comparative isolation, can occur but rarely in such a science as Meteorology. Hence Mr Milne Home's proposal for the plantation of Malta seemed to offer an exceptional opportunity for progress. Many of the conditions are favourable to the simplicity of the result; and it seemed natural that, if a searching and systematic series of observations were to be immediately set afoot, and continued during the course of the plantation and the growth of the wood, some light would be thrown on the still doubtful question of the climatic influence of forests.

At a recent meeting I laid before the Society a short notice of a phenomenon exhibited by the fluid contained in the cavities of calcareous spar. This phenomenon had been observed only a few days before, and the notice was given for the purpose of directing to it the attention of other observers, and particularly of those who happen to possess other minerals with analogous cavities, and I now propose to give an account of some more recent experiments and observations in regard to it.

Professor Tait having asked me to communicate to the Society some experiments I have made from time to time on the property of the retina discovered by him, and communicated to this Society, 15th January 1872, I prepared the following notes. It will be remembered that he pointed out that when the eye has been rested for a long time the first impression of light gives a red colour. Professor Crum Brown stated at the same meeting, that after Professor Tait had told him of the appearance he had himself observed a like phenomenon. Awaking one morning at grey dawn, and opening his eyes suddenly, he saw a glare of red on the window, and was so struck by it that he hastily rose to discover what house was on fire.

From researches which have much engaged my attention for nearly twenty years, I am convinced that silica performs a very important part, not only in the formation of the earth's crust, but also in leading to violent subterranean movements. The low specific gravity of silicic acid, and of the rocks in which it predominates, would (if much of the internal earth were fluid) give rise to certain results, which I traced in an essay published in 1856, and also in a paper which was brought before the British Association for the Advancement of Science in 1861.