character of the snow which fell on the 26th of December is thus easily understood. On the 7th of January, between 4 and 5 P.M., the sky overcast, and the thermometer standing considerably below the freezing point, Edinburgh was visited by another snow shower. On this oc casion the shower was of a very peculiar kind, for the stellate groups of crystals, instead of being aggregated into flakes, as in the shower of the 26th December, were for the most part isolated and distinct, so that the whole atmosphere was filled with separate ice-stars in inconceivable multitudes, whirling through the air, and drifting past one another in mazy paths which no eye could follow, so endless were their intersections, and inextricable their labyrinths; the wonderful ice-drift heaping itself up like white sand on the surrounding objects, but when projected against dark surfaces, revealing itself in all the unrivalled symmetry and beauty of its starry atoms. The chief difference between the present snow shower and that which fell on the 26th December, consisted in the segregation of its crystalline particles. There was a brisk breeze stirring at the time, in the lower regions of the atmosphere, and this was doubtless the invisible analyst that broke up the snow-flakes into their component elements, and flung them in stars and flowers to the earth. The following Note from Mr Stephens to Dr Balfour was also read : REDBRAE COTTAGE, 14th January 1861. MY DEAR SIR,-In December 1859, I was visiting Sir Robert Peel at Drayton Manor, in Staffordshire; and while there, a very heavy hoar-frost occurred for nearly two days,-every tree and shrub and the grass was fringed with most beautiful silver filagree. When walking along the shrubbery in the forenoon, I was led, from the remarkable exuberance of the hoar-frost, to examine it more minutely than by a casual glance; and to my surprise and delight, I perceived that the crystals presented quite a different arrangement on different bushes of evergreens. This there was no doubt of, as I could easily discern the difference in the arrangement of the crystals by the help of a large magnifying glass which I always carry with me when I go from home. I regret I did not take a sketch of the different arrangement of the crystals; but not being prepared for such a proceeding, and being no hand at sketching, I contented myself with looking from one bush to another. And while thus engaged for some time, I thought I made an interesting discovery—namely, that while different bushes presented a different form of crystallisation, the same sort of bush presented the same form of crystals. This discovery interested me very much-for discovery I deemed it, not having observed any mention of such a thing in any book on meteorology I have seen. Thus, Portugal laurels, laurel bays, laurustinas, different NEW SERIES.-VOL. XIII. NO. II.--APRIL 1861. I 2 s sorts of Arbor-vitæ, the yew, some of the new pines, presented different forms of crystals, but the same kind of plant had the same form of crystal. This I made sure of by repeated observation in different parts of the shrubbery; and more than that, the size of the crystals was about in proportion to the size of the leaves of the evergreens. Thus, the crystals in the Portugal laurel, laurel bays, and larger leaved kinds of evergreens, were larger than on the leaves of the laurustina, and these latter larger than in those of the yew and Arbor-vitæ. The crystals, moreover, were not spread over the surface of the leaves, but only along their margins; and the leaves above, that were exposed fully to the air, had the crystals-those within the bush, or under shelter of the leaves above them, were free of all hoar-frost. I may mention that the sun was obscured the first day by a frost-fog; the second day was clear, but the crystals retained their form where the sun did not strike; and on the following morning, the whole fairy scene had disappeared. Tall grasses and sedges by the side of a lake presented different crystals, but the same kind of plant similar forms. The naked branches of trees presented similar results. I am, &c., HENRY STEPHENS. 2. The Bifilar Magnetometer: its Errors and Corrections. By John Allan Broun, F.R.S., Director of the Trevandrum Observatory. Communicated by Professor Tait. 3. On the Horizontal Force of the Earth's Magnetism. By John Allan Broun, F.R.S., Director of the Observatory of the Rajah of Travancore. Communicated by Professor Tait. The conclusions of this paper are derived from observations made at Makerstoun in Scotland; Toronto, Canada; Trevandrum, Travancore, and Singapore, East Indies; St Helena, the Cape of Good Hope, Hobarton, Van Dieman's Island, &c. The author has corrected and discussed all the observations published made in the colonial observatories. The observations have been found affected by different errors, and frequently the series have been broken. An attempt has been made to correct these series; and, in general, to render the series as near the truth as possible. 4. Notice of an Instrument intended for the Measurement of Small Variations of Gravity. By John Allan Broun. Communicated by Professor Tait. 5. On the Law of Growth in Woody Circles of Exogenous Trees, as indicated by the Examination of a Single Specimen. By Principal Forbes. Monday, 18th February 1861.-The HON. LORD NEAVES, V.P., in the Chair. The following Communications were read :— 1. On the Embryology of Asteracanthion violaceus (Linn. Sp.) By Wyville Thomson, LL.D., F.R.S.E., M.R.I.A., F.G.S., &c., Professor of Natural History in Queen's College, Belfast. From the author's observations, it appears that the first step in the development of this form of echinoderm embryo is the differentiation of a portion of the yolk into an investing layer of structureless "Sarcode;" that the layer gradually increases in thickness; and that finally, from one part of its surface, a branched peduncular process is produced, as an extension of the same transparent structureless material. The branches of this organ are terminated by suckers, and serve, among other functions, as organs of locomotion. When fully formed, they are undistinguishable in structure and function from the ambulacral feet of the star-fish; a fluid undistinguishable from the chylaqueous fluid of the ambulacral system moves in them with the same characteristic motion. The peduncle is closed externally, no communication, except by transudation, existing between its cavity and the surrounding medium. At first it communicates with the general cavity of the embryo, but afterwards it becomes connected with, and part of, the ambulacral circulating system. When the ambulacral vessels and suckers of the young starfish become fully developed, this provisional vascular tuft disappears, leaving no apparent scar. In the species described, the peduncle is not connected in any way with the madreporic tubercle, which is not developed till long after its disappearance, and then on the opposite surface of the body. The peduncular appendage seems to be essentially a provisional development of the ambulacral vascular system, and to be functionally analogous to the omphalo-mesenteric and umbilical vessels of the vertebrate groups, endowed, however, with a greater amount of versatility of function, corresponding to that of the peculiar vascular system of which it forms a part, and to a great degree dependent upon the peculiar vital properties of the substance entering into its structure. 2. Some Observations on the Albino. By John Davy, M.D., F.R.S. Lond. and Ed., &c. The subjects of these observations were five individuals-four females, one male-all natives of Ceylon, of its south-east salubrious coast, and the children of coloured parents. They are described by the author as well made, as having good health, and, though all coming under the denomination of Albinos, on account of their unusual fairness, yet as varying in degree, the lightest having red eyes and almost white hair; the less light, blue eyes and light-brown hair, with a complexion that in this country would be considered merely that of a pure blonde. It would appear that the Albino in Ceylon, contrary to what has been asserted, is not held in contempt, but rather in respect, in accordance with the feeling of the people towards persons of high caste, who are almost invariably of a lighter hue than the more laborious and exposed low caste. A speculation of the Singalese is mentioned relative to the white races, viz., that they are the descendants of Albinos, and, ab origine, merely an accidental variety. The author seems to think that analogy is not unfavourable to this hypothesis, keeping in mind how great is the variety of colour, and its gradations from light to dark, amongst Europeans, and, in the instance of our domesticated animals, how colour is hereditary; and also on the ground that the sun's rays have a greater darkening effect on persons of brown skin than on those of fair; and that the former, especially the darkest-the blacks-are better able to resist malaria and the effects of tropical climates than the whites, and have thereby a better chance of escaping disease, and a premature death and extinction of race. 3. Note on the Bisulphide of Iodine. By Frederick Guthrie. 4. Notice of an Expeditious Method (believed to be new) for Computing the Time of Descent in a Circular Arc. By Edward Sang, Esq. 5. Note on a Modification of the Apparatus employed for one of Ampère's Fundamental Experiments in Electrodynamics' By Professor Tait. My attention was recalled by Principal Forbes's note (read to the Royal Society on January 7th), to his request that I should at leisure try to repeat Ampère's experiment for the mutual repulsion of two parts of the same straight conductor, by means of an apparatus which he had procured for the Natural Philosophy Collection in the University. Some days later I tried the experiment, but found that, on account of the narrowness of the troughs of mercury, it was impossible to prevent the capillary forces from driving the floating wire to the sides of the vessel. I therefore constructed an apparatus in which the troughs were two inches wide, the arms of the float being also at that distance apart. Making the experiment according to Ampère's method with this arrangement, I found one small Grove's cell sufficient to produce a steady motion of the float from the poles of the pile; in fact, the only difficulty in repeating the experiment lies in obtaining a perfectly clean mercurial surface. Two objections have been raised against Ampère's interpretation of this experiment, one of which is intimately connected with the subject of Principal Forbes's note. This is the difficulty of ascertaining exactly what takes place where a voltaic current passes from one conducting body to another of different material. It is known that thermal and thermo-electric effects generally accompany such a passage. Το get rid of this source of uncertainty, I have repeated Ampère's experiment in a form which excludes it entirely. In this form of the experiment the polar conductors and the float form one continuous metallic mass with the mercury in the troughs; the float being formed of glass tube filled with mercury, with its extremities slightly curved downwards so as nearly to dip under the surface of the fluid; and the wires from the battery being plunged into the upturned outward extremities of two glass tubes, which are pushed through the ends of the troughs so as to project an inch or two inwards under the surface of the mercury. A little practice is requisite to success in filling the float and immersing it in the troughs without admitting a bubble of air. This float, being heavier than the ordinary copper wire, plunges deeper in the fluid, and encounters more resistance to its motion, but, with two small Grove's cells only, Ampère's result was easily reproduced, even when the extremities of the float rested in contact with those of the polar tubes before the circuit was completed. It is obvious that here no thermo-electric effects can be produced in the mercury, and I have satisfied myself that the motion commences before the passage of the current can have sensibly heated the fluid in the tubes. The other class of objections to Ampère's conclusion from this experiment, depending on the spreading of the current in the mercury of the troughs, is of course not met by this modification. I have made several experiments with a view to obviate this also, but my time has been so much occupied that I have not been able as yet to put them in a form suitable for communication to this Society. Royal Physical Society. Wednesday 28th November.-WILLIAM RHIND, Esq., President in the Chair. The President delivered an Opening Address. The following communications were read : 1. Observations on British Zoophytes and Protozoa. (1.) Notice of Ophryodendron abietina (Corethria sertularia). (2.) On the Reproductive System of Chrysaora. By T. STRETHILL WRIGHT, M.D. (1.) On Ophryodendron abietina.-The author stated that, amongst the lower classes of animals, and especially in the Protozoa, the lowest |