Dec. 23, 1869] 
NATURE 
225 
DUBLIN 
Royal Irish Academy, December 13.—The Rey. Professor 
Jellett, president, in the chair. Professor Sullivan, Ph. D., read 
a paper on the Beds of Thenardite of the Valley of Jarama, in 
connection with climatal effects supposed to be due to the varia- 
tion of the eecentricity of the earth’s orbit, according to the 
calculations of Messrs. Crolland Moore. The author remarked 
that M. Adhemar 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. Atthe 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 Lever- 
rier’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, sup- 
posing 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 occurred 
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 respec- 
tively. Professor Tyndall has well pointed out that glaciers re- 
quire 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 pheno- 
menon 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 has been cut. The formation 
of anhydrous sulphate of soda requires that the solution from 
which the salt separates should be above 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 sul- 
phate of soda could be 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 be difficult to account for them on the sup- 
position of a period of intense cold. These beds were fully 
described in a paper by Professors Sullivan and O'Reilly, pub- 
lished in 1863 in Vol. iv. of the Afantis, 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 tcok part 
in the discussion of the paper. J. R. Garstin, A.M., was elected 
a member of council in the room of Professor Jellett. 
Paris 
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 NATURE, 
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 had 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 NATURE, 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 Goupilliére pre- 
sented a memoir on the system of metallic floodgates which re- 
quire 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 light 
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. I. J. Mau- 
mené 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 sugar, 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 to 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 formule 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 Pen/acrinus 
europaeus, 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 un- 
known in the countries south-west of the Euphrates until the 
time of the shepherd kings, or about the nineteenth century B.c. 
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 Aguas; 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 shep- 
herd 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 Prehis- 
toric Archzeological 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. Gueérin-Meneville 
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. Thuau on a process for the in- 
stantaneous lighting and extinction of gas-lamps by means of 
electricity. 
