Page:Nature - Volume 1.pdf/239

Dec. 23, 1869]

Royal Irish Academy, December 13.—The Rev. Professor Jellett, president, in the chair. Professor Sullivan, Ph.D,, read a paper on the Beds of Thenardite of the Valley of Jaramo, in connection with climatal effects supposed to be due to the variation of the eccentricity of the earth's orbit, according to the calculations of Messrs. Croll and Moore. The author remarked that M. Adhémar endeavoured to account for change of climate in geological time by the precession of the equinoxes, and the change of position of perihelion. These effects are modified by another astronomical movement—the change in the eccentricity of the earth's orbit. At the instance of Sir C. Lyell, Mr. Stone made some calculations to determine the eccentricity of the orbit in former periods, which Mr. Croll, by the aid of Leverrier's formula, has completed for one million years before 1800 in parts of a unit equal to the mean distance of the earth from the sun. These calculations are given by Sir C. Lyell in the last edition of his "Geology," with the addition of some calculations made by Mr. John Carrick Moore, of the mean temperature of the hottest and coldest months in the latitude of London, supposing other causes which may influence the distribution of heat to remain the same as at present. According to these tables, several periods of extreme temperature should have occured within the million of years. The most marked of them should occur At 200,000, 210,000, and 750,000 years before 1800, when the mean temperature of the hottest month should be 113° Fahr., and of the coldest 1°⋅9, 0°⋅7, and 0°⋅6 respectively. Professor Tyndall has well pointed out that glaciers require heat as well as cold to produce them, so that extreme temperatures appear to represent the conditions required. These views appear to receive an unexpected support from a phenomenon which, being purely physical, gives more definite results than can in general be obtained from biological ones. In the Valley of the Jarama, a branch of the Tagus which receives the waters of the Manzanares, which flows through Madrid, occurs a series of beds,—thenardite, glauberite, gypsum, and clay—having a variable thickness of from 16 to 19 metres. Through this the alluvial plain of the river bas been cut. The formation of anhydrous sulphate of soda requires that the solution from which the salt separates should be ahove 35° Cent. or 95° Fahr. This is a temperature which even a shallow lake could only attain if the temperature of the air were considerably above that point. On the other hand, the conditions under which the sulphate of soda could he formed in the first instance requires a low temperature. So that, like glaciers, these beds require great heat and cold, the limits of which are, however, fixed in this case. If the temperature of the hottest month in the latitude of London were 113°, it would be still higher on the plain of Madrid, where even 120° Fahr. in the shade is sometimes even now attained in the locality of these beds, The circumstance which should exist at either of the glacial periods indicated by Mr. Croll's and Mr. Carrick Moore's calculations, would be sufficient to account for those beds; it would he difficult to account for them on the supposition of a period of intense cold. These beds were fully described in a paper by Professors Sullivan and O'Reilly, pubished in 1863 in Vol. iv. of the Atlantis, and afterwards in "Notes on the Geology and Mineralogy of the Spanish Provinces of Santander and Madrid." (London: Williams and Norgate. 1863.) Professors Apjohn and Hennessy took part in the discussion of the paper. J. R. Garstin, A.M., was elected a member of council in the room of Professor Jellett.

Academy of Sciences, December 13.—M. H. Sainte-Claire Deville brought under the notice of the Academy a siderostat constructed by the late M. Léon Foucault, and communicated a note upon it by M. C. Wolf, Its action depends upon the production of a perfectly plane mirror, the mode of obtaining which was described in a posthumous paper by M. Léon Foucault, read to the Academy at a recent meeting (see, P. 177), and its object is to furnish the observer with a perfectly reflected image of any sidereal body for examination by the telescope. A figure of the instrument, which is provided with a clockwork movement, is given in illustration of M. Wolf's note.—M. Laugier remarked upon the employment of the plane mirror, and noticed that Arago bad called attention twenty years ago to the advantages which might be derived from it. M. P. A. Favre presented some remarks upon the electric explorer described by M. Trouvé (see, p. 177), for the detection of metallic substances in wounds, and claimed for himself the invention, in 1862, of an electrical sound for the same purpose.—Marshal Vaillant announced that M. Pasteur was engaged at Trieste in completing a work upon sericulture, and in organising a silk-worm cultivation on a large scale, to be carried on in accordance with his system,—M. Haton de la Goupillière presented a memoir on the system of metallic floodgates which require the minimum of attraction.—A memoir on the dispersion of light, by M. M. Ricour, was communicated by M. Combes. General Morin presented a note by M. H. Morton, on the origin of the luminous band which is observed in contact with the margin of the moon's disc in the photographic pictures of various eclipses. In preparing negative photographs of eclipses, a slight band surrounds the border of the moon's shadow, in which the deposit of silver is more dense than elsewhere, producing a slight band in that positive. The author has produced a similar effect by substituting a disc of dark paper for the moon's shadow, and he comes to the conclusion that the phenomenon is simply chemical, and due to the extension, during the development of the plate, of the nitrate of silver from the part protected by the shadow, to a short distance beyond the latter.—A note by M. Hugo Schiff, on the constitution of amygdaline and phloridzine, was communicated by M. Wurtz. The author describes and formulates these substances and their derivatives.—M. E. J. Manmené communicated another memoir on inverted sugar, in reply to M. Dubrunfant, in which he states that none of the latter's assertions are in accordance with experiment. He says that inverted sugars, properly prepared, is a mixture of three optically neutral bodies, which are neither glucose, nor levulose, nor any of the sugars possessing a rotatory power. The fermentation of inverted sugar is accompanied by no elective phenomena.—M. Dubrunfant presented a communication on spectrum analysis applied to the investigation of simple gases, and of their mixtures, in which he described the phenomena presented by various gases and gaseous mixtures under different conditions of pressure, and indicated that the supposed multiple spectra of certain gases are probably due to admixture. Thus it appears to be impossible ta obtain hydrogen free from nitrogen, and under a low pressure the spectrum of the latter alone appears.—M. Jos. Boussingault communicated an analysis of the "morallon" emeralds from the mines of Muso, in New Granada.—A memoir was presented by M. Martin de Brettes on the determination of one or more of the following quantities, the others being given: The diameter of an oblong projectile, its weight, its initial velocity, the curve of its trajectory, and the weight of the gun from which it is fired. He gives the formulæ for working out these questions, and indicates their applications to artillery and small arms.—Of two zoological papers, one, by M. Lacaze Duthiers, calls the attention of naturalists to the Harbour of Roscoff, on the north coast of France, as a locality where the so-called Pentacrinus europœus, the young form of Antedon rosaceus, is to be found in abundance. From his description, the Bay of Roscoff is a paradise for the student of marine zoology,—The second memoir, by M. F. Lenormant, discusses the question of the antiquity of the ass and the horse as domestic animals in Syria and Egypt; and the author states, in opposition to Professor Owen, that the ass is represented very frequently upon the earliest known monuments. The horse, on the contrary, remained unknown in the countries south-west of the Euphrates until the time of the shepherd kings, or about the nineteenth century M. Milne-Edwards remarked upon this communication that it agreed with the conclusions of zoologists as to the distribution of the species of the genus Equus; the ass is to be regarded as an essentially African species, whilst the horse is a native of central Asia and part of Europe. He added that if the shepherd peoples introduced the horse into Egypt, this might throw some light upon their origin, M. Elie de Beaumont remarked that these facts were favourable to the opinion that the existing state of things on the surface of the globe was not of very ancient date.—M. J. Reboux communicated the results of some Prehistoric Archæological researches upon the quarternary beds of Paris, in which he indicated the character of numerous worked flints obtained by him from these beds (from a depth of twelve metres upwards), and gave a long list of animals, the remains of which were found intermixed with the flints—M. Guérin-Méneville remarked upon the conditions of production of truffles—A note was presented from M. Namias, describing his employment of hydrate of chloral with beneficial effects at the Hospital of Venice; and another from M. Thuan on a process for the instantaneous lighting and extinction of gas-lamps by means of electricity.