M. Leverrier further informs us that the explanations which M. Lescarbault gave him entirely satisfied him that the alleged observations were real, and are entitled to a place in science; that the long delay in making them public is due solely to the modest reserve of the observer, and the quietude of a residence remote from the excitement of great cities. In support of his assertions, M. Leverrier has exhibited the proofs which he found in the domicil of Dr. Lescarbault, viz. a paper on which the latter had marked, on the 26th of March, 1859, the appearance of the black point on the solar disc, and a pine board on which Dr. L. had chalked his computations and his drawings.

Hardly had these announcements been made, when several other similar observations were called to mind. Mr. Scott, Chamberlain of London, writes in Galignani's Messenger of January 14, 1860, that an Englishman, Mr. Lloft, observed, January 6, 1818, a black point traversing the sun's disc, and that he (Mr. S.) had made a like observation in the summer of 1847, had thence concluded the existence of a third inferior planet, and had so published. His son, five years old, standing by, was placed at the telescope, and confirmed the observation by crying out, "I see a little balloon on the sun."

M. Wolff of Zurich has published several ancient observations, which he thinks refers to the transit across the sun of an intra-mercurial planet, viz. by (1,) Scheutzer of Crefeld, June 6, 1761; (2,) Staudacher, towards the end of February, 1762; (3,) Lichtenberg, November 19, 1762; (4,) Hoffmann, at the beginning of May. 1764; (5) Dangos, January 18, 1798; (6) Fritsch, October 10, 1801; (7,) Stark, October 9, 1819. All these observers saw a round well-defined point, of the apparent diameter of Mercury, crossing the solar disc in a short period, varying from two to three hours. Using only the observations 5, 6 and 7, Mr. Wolff finds that they accord with the supposition of a planet having a revolution around the sun in 19-25 days, a result surprisingly near to that (19-7 days) deduced by M. Leverrier, from the observation of Dr. Lescarbault.

In settling the question, who is entitled to the credit of the discovery, it is clear that Dr. Lescarbault's observations are the first which have the scientific seal, and are of such a nature as to be subject of computation. New Members Elected.

FIZEAU was elected 2nd of January member of the section of Physics in place of Cagniard de Latour-deceased.

PLANA was elected March 5, foreign associate in place of LejeuneDirichlet deceased.

At the session of the Académie held March 19, Mr. J. A. SERRET was elected a member in the section of Geometry in place of Poinsot, deceased. Dausey has lately (March 12) communicated to the Academy a memoir, setting forth the geographical and physical observations of Hommaire de Hell made in 1846-48 in Turkey and Persia, where he died at Ispahan in August, 1848. His manuscripts were taken to France by Jules Laurent the well-known artist who accompanied the expedition. Dausey reports the barometric and astronomical determinations of much value.

Hypnotism and Magnetism.-French society has been almost carried away with a kind of scientific epidemic which may be compared to the

SECOND SERIES, VOL. XXIX, No. 87.-MAY, 1860.

malady called "table tipping," which was so much in vogue a few years since. This epidemic is Hypnotism or nervous sleep. It was brought into notice by a French surgeon following a work of Dr. Braid (published 15 years since), in which this physician, describes under the name of Hypnotism, the nervous affection which is produced under the following circumstances:-When a brilliant object is placed directly before the face at a distance of from 8 to 15 inches, and the subject of the experiment is requested to fix his eyes steadily upon the object, in such a way as to produce a permanent contraction of the muscles of the eye and eyelid, there will be seen to come on, after the lapse of a few minutes, a state analogous to catalepsy. M. Broca, having successfully employed hypnotism in producing insensibility to pain, proposes it to surgeons as an anaesthetic agent capable, in many cases of being substituted in practice for ether or chloroform, "because," as he remarks to physicians, "this method, introducing as it does no substance into the system, appears to me absolutely harmless." From the numerous experiments which have since been made, it results; 1st, that this kind of anesthesia can be developed but rarely, and in persons whose nervous system is especially predisposed; 2nd, that hypnotism may give rise to attacks of epilepsy.

This kind of anesthesia is therefore not less open to objection than the other. Its origin is more ancient than is supposed; it was established more than two centuries ago, under the name of irradiation or phenomena of actinobolism, by P. Kircher in his Ars magna Lucis et Umbræ.

It is concluded that in hypnotism is seen only a fact in the domain of animal magnetism, which is not yet a science. We will not enter further into the details.

Porous bodies.-Among the topics of scientific interest which awaken attention at present, is the research of Jamin, professor at the École Polytechnique, upon the equilibrium and movement of fluids in porous bodies. The new results at which he has arrived afford an explanation of the ascent of the sap in vegetables without the necessity of recourse to the vital force. It is apparently a question of capillarity only.

Jamin has applied the new facts which he has discovered to the construction of an apparatus composed entirely of inorganic materials, but showing in its structure a great analogy with vegetables. This apparatus has the property of raising water as trees do, to a height greater than that attained by means of atmospheric pressure, from a moist soil whence the water is constantly drawn to the factitious leaves where it is continually evaporated.

Reduced to its most simple form this apparatus is composed of a block of some well dried porous substance as chalk, lithographic stone, &c., or a porous battery cell filled with a powder well rammed in, white chalk for instance, oxyd of zinc, or even with earth. A manometer is imbedded in the interior of the mass, and the whole is plunged in a vessel full of water. The water immediately penetrates its pores and drives out the air, which collecting in the interior, exercises a pressure upon the manometer amounting with oxyd of zinc to five atmospheres and with starch it exceeds six atmospheres. This is not the limit of the greatest possible pressure; Jamin makes known the causes which diminish it in these cases and proves that the water is forced into porous bodies with a force which he calls, and which is equal to that of a considerable number of atmospheres.

A tube 1.20 metres long filled with plaster and terminated at the summit by an evaporating surface is inserted by its base into a reservoir closed and filled with water; a vacuum is caused measured by 15 or 20 millimetres of mercury or by 200 or 270 millimetres of water; and the water appears even at the upper extremity of the tube, which proves that porous bodies are able to raise water higher than can be done by atmospheric pressure. These facts cannot be explained by the ordinary laws of capillary attraction, since these bodies are not formed of impermeable tubes, but of corpuscles in juxtaposition, separated by small empty spaces. Jamin has therefore submitted the problem to the calculus and has come to results, of which we mention the following:

If in a damp porous body, the water is compressed by a power of several atmospheres, it can congeal only at a temperature below 0° C.* Consequently the old wood is able to resist frost, while the young shoots being less dense are unable to do so.

Since water in filtering through a porous body is compressed as it enters and dilates again as it runs out, it should exhibit electric currents and many other phenomena.

The theory can not be applied to non-homogeneous porous bodies. In the extended memoir which he has prepared, Jamin discusses the complicated results which may be occasioned by irregularity of structure; he makes an application of it to wood, and shows that the interior pressure must be augmented in the denser tissues; that the air must come from the larger tubes, which cannot serve for the ascent of the sap.

It is plain that the evident tendency of all these experiments is to explain the ascent of the sap in vegetables by capillarity. The idea is not new, but it has not been hitherto fully admitted, notwithstanding the experiments which have been heretofore made.

Jamin gives it probability in showing by decisive experiments, that porous bodies exercise a capillary action superior to the pressure of the atmosphere; further, he gives the physical theory of capillarity in porous bodies and succeeds in calculating the phenomena of the movement of liquids in trees, This is thoroughly physiological. If the Academy of Sciences could award the great prize for physiology, for a work upon fermentation, when it is not yet known whether this purely chemical phenomena is the result of vital action as Cagniard de Latour maintains, or the manifestation of a mechanical effect as Liebig explains it, in his beautiful theory of fermentations,-if this work in chemistry deserved the great prize for experimental physiology for a stronger reason should they award this prize for the splendid physical researches of which we have just spoken. Application of electric light in Medicine. The ordinary processes of illumination are of very difficult application when the object is to employ artificial light in diagnoses or in certain cases in operative medicine, inasmuch as the illumination is insufficient, or the light is more or less colored, and is accompanied with heat. It is not the ordinary electric light here spoken of, but that produced by induced currents. The problem to be solved consists in finding a source of light with little or no heating effect, which can be compressed into tubes of small capacity and of forms adapted

This fact has just been demonstrated by Mr. Sorby for water contained in capillary tubes of a small diameter.-J. N.

to circumstances, and which finally is of such whiteness as not visibly to alter the color of organic, tissues illuminated by it. This problem has just been solved by Dr. Fonssagrive, physician of the naval school at Brest, with the coöperation of Messrs. Ruhmkorff and DuMoncel. The apparatus consists of an empty tube of Geissler, of very small diameter folded and turned upon itself after the manner of multipliers; this tube contains a gaseous mixture which gives a perfectly white light when it is traversed by an electric current produced by an induction coil.

Phosphorescence.-The electric lamp (photophore) of which we were just speaking calls to mind some observations upon phosphorescence which have just been made by Phipson; he has found that like cane sugar, the sugar of milk or lactine becomes luminous by concussion, and also by fracture. To evolve phosphorescence from the nitrate of uranium, it is sufficient to shake briskly a bottle containing a certain quantity of this salt in the crystalline state. The light is very vivid when the experiment is made with one or two kilograms of this substance. Calomel possesses the same property, although in a less degree.

Works of Arago. The sixteenth and last volume of Arago's works has just appeared. It contains a great number of unpublished researches made by Arago during his career.

The sixteen triangles are here given which Messrs. Biot and Arago determined in the prolongation of the meridian of France to the island of Formentera. Arago alone, has measured besides, a seventeenth triangle having its summit at the enclosure of Galaro in the island of Majorca and resting in one direction upon Camprey in the island of Trizza, and the other upon the mole of Formentera, with the design of obtaining the length of an arc of the parallel nearly 3° from the extremity of the meridian, and to determine the curvature of that portion of the earth's surface. The results of these measurements, heretofore unpublished, are found in this volume.

Arago in the year 1853, the very year of his death, communicated to the Academy a memoir upon the figure and physical constitution of Mars, which is likewise contained in this volume, and is accompanied by more than 3000 micrometrical measurements of the diameters of Mars, Jupiter, Saturn and Uranus, which were taken from 1811-1847.

It is well known that Arago made numerous investigations in regard to the refractive power of atmospheric air, dry or humid, and of different gases and vapors. He labored in this department for nearly half a century, namely, in 1805 with Biot, in 1815 and 1816 with Petit, and in 1852 with Fizeau. Chemists and physicists will derive much advantage from the determination of the refractive powers not only of some simple gases, but also of compound gases such as oxyd of carbon, carburetted hydrogen, sulphuretted hydrogen, cyanogen, the vapors of sulphur and of carbon, of sulphuric ether and chlorohydric ether.

This volume also contains studies upon optics, atmospheric electricity, &c. United to the other fifteen volumes it forms a lofty monument to science as well as to one of its most noble representatives.

Bibliography.-The following works have just appeared at Paris.

Oeuvres d'Arago, Tom. xvi, 1859; chez Gide, 5 rue Bonaparte.-This volume is devoted to scientific notices bearing upon the personal labors of Arago, many of which have never before been published.

At the Librarie centrale des sciences rue de Seine; Recherches sur le non-homogé néité de l'étincelle d'induction, par M. TH. DU MONCEL, 1860.-M. du Moncel, who gives all his leisure to the study of electricity and its applications, presents in this brochure the result of his researches upon the electric spark, and especially the spark of induction, of which the non homogeneity was discovered by him in 1855. At Baillière Bros., Paris & New York. Traité èlementaire de Physique expérimentale, Tom. 1. 12°, 1860, par M. FORTHOMME, professor of Physics at the Lyceum in Nancy. This work, even by the confession of the author, contains nothing new, but is distinguished by its method. The most difficult questions in regard to gravity, hydrostatics and heat are explained in the first volume with great clearness, and thus rendered intelligible to persons little versed in these matters, which are so important in our day and have so many useful applications.

By Lacroix & Baudry, Quai Malaquais.-Grands hommes et grandes choses, notices scientifiques sur les inventions et sur les decouvertes modernes et sur les auteurs, par Victor Meunier. 8°, 1860-This work appears by numbers, once a week; its author, of whom we have often spoken, has acquired in France a great reputation as a popularizer. He established the Ami des Sciences, a journal for scientific discussions, which he has directed for six years, and is remarkable for the independence of his opinions and judgments. M. V. Meunier in this new publication proposes all the great scientific questions of the day.

ART. XXXVIII.-Description of an Equatorial recently erected at Hopefield Observatory, Haddenham, Bucks; by the Rev. W. R.

DAWES.

(From the Monthly Notices of the Royal Astronomical Society.)

My observatory was furnished, in May last, with an equatorially-mounted telescope by Messrs. Alvan Clark and Sons, of Boston, U. S., which in several important points differs from any other in this country; and I therefore hope that a brief description of it may not prove uninteresting to the Royal Astronomical Society.

The form combines great firmness and compactness with considerable elegance of design. The massive part of its structure is of cast-iron, the base of which is firmly bolted down to a stone pier. The semicircular form of the upper part affords a secure position for most of the wheel-work of the driving-clock, of which the going-weight descends in a groove on the east side of the pier, and is not seen in the drawing. The space between the polar axis and the semicircular bed-piece is occupied at its lower part by the hour-circle. Immediately above this is a sector, which clamps on to the axis, and the wheel-work of the clock occupies the upper portion. The sector has a radius of rather more than 9 inches and an arc of 30°, or two hours of right ascension. This arc has a face of an inch and a half in breadth, between which and a cylinder 7 inches in circumference there is just room enough for two thin bands of sheet-brass, each of about three-fourths of an inch in width, to pass side by side. These bands are both keyed by the end into one groove in the cylinder, at such a distance that they cannot overlap or interfere with each other. They are then bent round the cylinder in