served, according to the degree of concentration of the solution. The metals on which these experiments were made are didyme, erbium, and terbium.

Dr. W. Marcet read two memoirs: one on a colloid acid derived from urine, in which some new details were added respecting the chemical properties and atomic weight of this acid; the second memoir (Bib. Univers., Archives, &c., vol. xxii) had for its object the muscular dialysis, M. Marcet proving in this paper that the muscular substance is permeable for colloid as well as crystallizable substances. M. Chaix offered some remarks on the accumulation of volcanoes, whether extinct or in activity, with which recent explorations have made us acquainted in certain regions of the globe, particularly in the republic of Nicaragua and in New Zealand. He also indicated, on the authority of a memoir of M. Abich, the appearance of several new islands, which have emerged in the Caspian sea, as a sequel of volcanic movements in 1857 and Dr. Pitschner read an account of his ascension of Mont Blanc in 1859, during which he took occasion to make observations on different points of terrestrial physics, physiology, and zoology.

1864.

NATURAL SCIENCES.

Professor Favre presented to the society a memoir, (Bib. Univers., Archives, &c., vol. xxii,) in which he recapitulates, from an historical point of view, the discussion which has taken place on the subject of the coal formation of the Alps, and announces the conclusions at which he has arrived from his observations made in different parts of those mountains. The study of the chain of Mont Blanc formed the subject of two memoirs read by M. Favre; in the first, he occupies himself with the fan-shaped structure of that group, and after having discussed the different theories advanced on this subject, he concurs in the opinion pronounced by M. Lory, adding some considerations on the protogene of which the chain is formed. In the other memoir he undertakes to investigate the succession and thickness of the strata which must have covered that part of the surface of the earth before the mass of Mont Blanc made its appearance and upheaved the formations which covered it. These formations have been gradually removed by the action of atmospheric agents, and thence has resulted an enormous denudation, laying bare the protogene. M. Favre seeks to calculate the volume gauged by the formations thus removed, and he shows that the greatest elevation of the chain, before these denudations, may explain in part the greatest extension of the glaciers. Our colleague, lastly, read to the society his letter, (Bib. Universelle, Archives, &c., vol. xxii,) addressed to Sir R. Murchison, in which he combats the theory of the excavation of the alpine lakes and valleys by glaciers. It was the study of the lake of Geneva and of the direction of the geological strata on the two shores, whether in the eastern or western part, which furnished M. Favre with proof that the depression of the bed of the lake must have proceeded from a cause wholly different from an excavation by glaciers.

Professor Pictet presented a memoir (Bib. Univers., Archives, &c., vol. xxi) on the succession of gasteropod mollusks in the cretaceous lakes of the Jura and the Swiss Alps. The study of the fossils collected at Sainte Croix has enabled him to recognize in that locality the existence of nine successive faunas, independent of one another and almost without mixture, between the epoch of the lower valangian and that of the chloritic chalk of Rouen. A comparison with the cotemporaneous faunas of the neighboring countries shows that the species are there associated somewhat differently, and hence M. Pictet concludes, from analogy with what occurs in our present seas, that we cannot consider each species as characteristic of the whole of a period. It must rather be admitted, contrary to an opinion quite widely entertained, that the greater part of species have a variable signification, according to the geographic region where they are

found. Professor Pictet also presented a memoir, (Bib. Univers., Archives, &c., vol. xxii,) by MM. d'Espine and E. Favre, in which these two young savants, who had just finished their studies at the academy of Geneva, record their researches made in certain localities in the region of the Alps, where the faunas of the lower and the upper gault are found intermingled. The localities studied by them are la Goudinière, near the Grand-Bornand, the mountain of Criou, above Samoëns, and the Wannen-Alp, in the canton of Schwytz. To this memoir, presented for the annual competition founded as a parallel to the Davy prize, the premium was awarded.

M. de Loriol read a memoir (Memoires de la Société de Phys. et d'Hist. Nat. de Genere, vol. xviii,) on the infracretaceous fresh-water strata of Villers-le-Lac, (Doubs,) in which he arrives at the following conclusions: the Portlandian dolomites of the Jura are the equivalent of the Plattenkalk of Hanover and of the limestones à plaquettes of the Charente; they do not pertain to the Portlandian, and they form the base of the Purbeckian group. The fresh-water limestones and marls of Villers are the equivalent of the Mundener Mergel and serpulite of Hanover, as well as of the gypsiferious clays of the Charente. Again, this infracretaceous group of Villers and the Jura is the equivalent of the Purbeck beds of England, of which they represent the middle and the lower part.

M. Humbert presented a memoir (Memoires de la Soc. de Phys. et d'Hist. Nat. de Geneve, vol. xviii) on the myriapods of Ceylon, of which he had an opportu-. nity of collecting a great number of individuals during his sojourn in that island. The author draws the attention of naturalists to certain organs, heretofore little studied, and which furnish important characters for the establishment of genera and species. M. de Saussure presented to the society a new number of his work on the orthoptera of Mexico. This number is devoted to the family of Blattæ, several specimens of which the author exhibited, and respecting which his researches have led him to verify some interesting facts. He points out, among others, a very singular peculiarity in the structure of the wing of a tribe of this family, to which he has given the name of diplopterians. In these insects the wing is folded into four duplicates which are exactly superposed by means of a longitudinal and a transversal crease; it is by gradual modifications that the structure of the wing deviates more and more, in the three genera established in this tribe by M. de Saussure, from the normal type of duplicature which occurs in the orthoptera.

M. Fatio exhibited to the society an apparatus, (Bulletin de la Soc. Ornithologique Suisse, vol. i,) to which he has given the name of oometre, constructed with a view of determining the dimensions of the eggs of birds measured in all directions, and consequently their exact form. It might serve as well for the analogous measurement of shells. The same member gave information of a colony of ash-colored herons which he has discovered on the shore of the lake of Lucerne, at the foot of Mount Pilate; during an excursion made in that locality he ascertained the existence of from 200 to 300 nests of these birds. Professor Claparede made a report (Bib. Univers., Archives, &c., vol. xxii) on certain interesting results at which Dr. Fritz Müller has arrived in his studies of the crustacea of the island of St. Catharina, on the coast of Brazil. On comparing the respiratory apparatus in the families of the land crabs which are derived from those of the marine crabs, M Müller found that the adaptation of this apparatus to aerial life is not accomplished by the same process in each family, whence the author draws a conclusion favorable to the theory of Darwin. Professor Claparede likewise presented us an analysis of the researches of Professor Wagner, at Casan, respecting certain larvæ of flies, in the interior of which small larvæ are developed, which issue forth by piercing the skin, and become like their mother; thus a series of generations of larvæ is presented, without the perfect insect having been obtained. Our colleague noticed also

the discovery made by M. Leuckardt of an interesting case of alternating generation in the Ascarides nigrovenosa.

M. Duby presented a report on the investigations of M. Bary; of Fribourg, in Brisgau, relative to certain parasitical fungi which are observed on the leaves of the cruciferæ. M. de Bary has discovered a sexual generation among these fungi, and has observed also a true alternating generation in certain kinds; hence, he has felt authorized to refer to one and the same species, fungi, which have been heretofore classified in different species and even in different tribes.. It is to one of these fungi, the Perenospora infestans, that M. de Bary attributes the malady of the potato.

Personnel. Our society has, in the course of the year, sustained the loss of one of its members in ordinary, M. Pyrame-Louis Morin, whom a premature death has torn from science and his country before he had completed his fiftieth year. In rapidly sketching the scientific career of our deceased colleague I shall not pretend to offer a complete portrait of a life so usefully and honorably occupied. I shall not speak of the devoted citizen who was animated with so ardent a love for his country, and who gave proof of an enlightened patriotism through the political agitations of the last twenty-five years. I shall not speak of the pharmaceutist who bestowed upon his preparations the same care and exactness which a consummate chemist applies to the most delicate analyses. Nor shall I speak of the services rendered by Morin to the industry of our city, for even now a voice much more eloquent than mine retraces the part which he has filled in the Society of Arts, and more especially in the class of industry to which he had dedicated for many years all the time at his disposal. I shall confine myself to a sketch of his career as a man of science and a member of our society.

Born at Geneva, in March, 1815, he was placed at the age of ten years in the institute of M. Naville, at Vernier, where he pursued his early studies, till admitted, in 1832, as a pupil at the Academy of Geneva to prosecute the scientific courses then comprised in the faculty of philosophy. His taste for chemistry, which was thus developed, naturally pointed out the path which he was to follow, and he joined his uncle, M. Antoine Morin, in order to fulfil, as a student of pharmacy, the apprenticeship of his new vocation. He afterwards passed two years at the University of Zurich, where he became preparator for M. Loewig and director of the laboratory of practical chemistry; he gave also in that city courses of chemistry applied to the arts.

He thence proceeded to Berlin, where he had the advantage of being placed under the special direction of M. Mitscherlich, and he here published his first scientific memoir, which had for its object researches on the bisulphurate of ethyle; this paper was inserted in the Annals of Poggendorf. He completed his practical studies in Paris, at the establishment then conducted by M. Soubeiran, and returning to Geneva in 1840 was admitted as pharmaceutist, after undergoing the examinations required at that period, embracing, as a qualifying test, an analytical disquisition on the red quinquina. At the close of that year he was received into our society, of which he was an assiduous attendant to the last, and an active participant in its labors. Among the memoirs which he published, most of which were presented to this body, are several which relate to the waters of Saxon, and to the long controversies which he was called to sustain in reference to that subject. In his second analysis, published in 1853, he had shown the intermission of iodine in that fountain, a result which was at first contested by MM. Rivier and Fellenberg, who were not slow, however, in recognizing the exactness of the facts advanced by Morin, and in conforming to his opinion. At a later date M. Ossian Henri, whose name was an authority, maintained the constant presence of the iodine, but contended that it was sometimes masked by a sulphurous principle. On this occasion Morin made new researches and a complete study of the subject, proving, among other things, that there

was no sulphurous principle in the water of Saxon, and establishing irrefutably, by a series of numerous quantitative analyses, that the constant existence of iodine therein was an illusion, and its intermission a reality.

From the very titles of the memoirs published by Morin it may be seen that his researches were chiefly directed towards a practical end, and that the numerous analyses which he conducted were undertaken with a view to application rather than to theory. But that in which we recognize the chemist, conversant with the entire progress and with every demand of the science, is the exactness and care with which all these analytical researches were made. It was this tendency towards the application of science to the arts which impelled Morin to devote himself more and more to the class of industry, that section of the Society of Arts in which he found the field of activity that best suited him. Although his health had been seriously affected for more than two years, his zeal and activity were not for a moment relaxed, and it was only since the month of September last that the progress of the malady obliged him to renounce his occupations. He died 1st of December, 1864, after many months of suffering, -bearing with him the regrets of his colleagues and of all who had known and could appreciate the worth of the man aud the savant.

I shall recall, lastly, the different nominations which have been made in the course of the year: M. Arthur Achard has been named as member in ordinary; M. Berthelot, professor of the normal school, and General Morin, director of the conservatory of arts and trades at Paris, have been elected honorary members; and Dr. Ed. Dufresne, associate at large. In the elections which have taken place for the renewal of the bureau, at the commencement of the year, you have called to the presidency Dr. Gosse; whence it will result that, by a happy coincidence, the same year which is destined to the celebration at Geneva of the fiftieth anniversary of the Helvetic Society of Natural Sciences, will be marked in our own association by the presidency of the son of that savant to whom Switzerland is indebted for an institution whose utility is every year more highly appreciated.

THE AURORA BOREALIS, OR POLAR LIGHT:

ITS PHENOMENA AND LAWS.

BY ELIAS LOOMIS,

PROFESSOR OF NATURAL PHILOSOPHY AND ASTRONOMY IN YALE COLLEGE,

THE Aurora Polaris is a luminous appearance frequently scen near the horizon as a diffuse light like the morning twilight, whence it has received the name of aurora. In the northern hemisphere it is usually termed aurora borealis, because it is chiefly seen in the north. Similar phenomena are also seen in the southern hemisphere, where it is called the aurora australis. Each of them might with greater propriety be called aurora polaris or polar light.

The aurora exhibits an infinite variety of appearances, but they may generally be referred to one of the following classes:

1. A horizontal light, like the morning aurora or break of day. The polar light may generally be distinguished from the true dawn by its position in the heavens, since in the United States it always appears in the northern quarter. This is the most common form of aurora, but it is not an essentially distinct variety, being due to a blending of the other varieties in the distance.

2. An arch of light somewhat in the form of a rainbow. This arch frequently extends entirely across the heavens from east to west, and cuts the magnetic meridian nearly at right angles. This arch does not long remain stationary, but frequently rises and falls; and when the aurora exhibits great splendor, several parallel arches are often seen at the same time, appearing as broad belts of light stretching from the eastern to the western horizon. In the polar regions five such arches have been seen at once,* and on two occasions have been seen nine parallel arches separated by distinct intervals.t

3. Slender luminous beams or columns, well defined, and often of a bright light. These beams rise to various heights in the heavens, 30°, 50°, 70°, and sometimes, though rarely, they pass the zenith. Frequently they last but a few minutes; sometimes they continue a quarter of an hour, a half hour, or even a whole hour. Sometimes they remain at rest, and sometimes they have a quick lateral motion. Their light is commonly of a pale yellow, sometimes reddish, occasionally crimson, or even of blood color. Sometimes the tops of these beams are pointed, and having a waving motion, they resemble the lambent flames of half-extinguished alcohol, burning upon a broad, flat surface. Sometimes the luminous beams are interspersed with dark rays, resembling dense smoke.

4. The corona. Luminous beams sometimes shoot up simultaneously from nearly every part of the horizon, and converge to a point a little south of the zenith, forming a quivering canopy of flame, which is called the corona. The sky now resembles a fiery dome, and the crown appears to rest on variegated fiery pillars, which are frequently traversed by waves or flashes of light. This may be called a complete aurora, and comprehends most of the peculiarities of the other varieties.

*Franklin's First Expedition, p. 588.

+ Voyages en Scandinavic, 1838, pp. 170-171.