companion of his youth, accompanied his remains even to their destination notwithstanding his great age and the severity of the season.

Magnetic force of Oxygen.-In 1849 M. Edmond Becquerel, Professor at the "Conservatoire des Arts et Metiers" in studying the action of electro-magnets upon various bodies, established that oxygen is magnetic and that atmospheric air in virtue of the oxygen it contains, partakes of the same property. The mode of experiment to measure the force exercised by a magnet on a gas in comparison with the effect produced upon a body taken as unity, consisted in placing successively small bars of glass, wax, &c., in a vacuum and in different gases, in order to determine the magnetic power of the gas by the difference of effect produced under these two conditions. He thus established that the relation between the attraction of oxygen by a magnet, and the repulsion in an equal volume of water, is proportioned to the density of the gas; and that it is represented by 0.18 at the temperature of 12° C.

If we reflect that the earth is surrounded by a mass of air equivalent in weight to a stratum of mercury 76 centimeters in height, we can understand that a similar mass submitted to the incessant variations of pressure and temperature, ought to exercise an influence on some of the phenomena dependent on terrestrial magnetism. In calculating what is the real magnetic power of this fluid mass we find that it is equivalent to an immense shell of iron of a thickness of th of a millimeter, covering the entire surface of the globe. M. Becquerel's rerulis have been confirmed by M. Faraday and by M. Matteucci by different methods. M. Plucker having reached other results by the use of a method of his own-a process by weight-Becquerel has revised his researches and confirmed anew the results previously announced.

Oxygen in the nascent state-Ozone.-For some time past, observations have been made in Europe on atmospheric ozone. Owing to the persevering efforts of MM. Wolf of Berne, D. Boeckel of Strasburg, and Dr. Simonin of Nancy, some general facts of the highest interest have been reached by the use of Schönbein's test (i. e. paper made sensitive by starch and iodid of potassium). According to these observations there exists an intimate relation between the quantity of ozone in the air and certain epidemic diseases such as cholera, grippe, intermittent fever, &c. They think they have established that the appearance of the grippe coincides with the presence in the air of an excess of ozone: that on the contrary the invasion of cholera is accompanied by an almost complete absence of ozone in the air; this is at least true for the places above named.t

It is well known that ozone is regarded as an isomeric or allotropic condition of oxygen. MM. Becquerel and Frémy have called it electrized oxygen and have prepared it, as we have before described, by submitting pure oxygen to the electrical current.

The following is a new mode of preparing it in abundance (or at least a similar body) capable of oxydizing silver, of decomposing iodid

* Faraday's results were published before 1849, in 1847, his first paper on the magnetism of oxygen having been read before the Royal Society in that year, and published in the Philosophical Magazine for Dec. 1847.-EDS.

It will be remembered that in 1849 much was said in the medical journals of this land, on the relation between cholera and ozone, the absence of ozone being insisted on at that time in cholera districts in the United States.-EDS.

of potassium, of burning ammonia, of disengaging chlorine from hydrochloric acid, and of forming water with hydrogen. This simple process consists in treating peroxyd of barium (BaO2) with monohydrated sulphuric acid at a temperature below 70° C. The oxygen disengaged in this process possesses the properties named above, and it has the characteristic odor which is known as the Lobster odor. M. Houzeau assistant to M. Boussingault, is the author of this process which he discovered during a series of researches on the preparation of oxygen from the peroxyd of barium by heat.

Attempts to insulate Fluorine.-M. Frémy has been for many years engaged in this research, employing as the means of decomposition the galvanic pile, and selecting for his experiments the fluorid of potassium obtained by the calcination of the fluohydrated fluorid of the same base (FIH+FIK) in a platinum crucible. The resulting fluorid is of difficult fusion and in order to submit it to the action of the pile, M. Frémy introduces it into a tubulated retort of platinum which is then submitted to the heat of a good forge fire. A platinum wire communicates the currents from the positive pole and enters the fused fluorid; the negative pole connects with the retort. The platinum reddens rapidly under this action, and is changed to fluorid of platinum which at that temperature is at once decomposed. From the neck of the retort a gas issues, which is strongly odorous; it decomposes water producing fluohydric acid. and displaces the iodine of the iodids. M. Frémy regards this gas as fluorine, and he has already prepared it many times in his laboratory at the Polytechnic School. It is in other respects identical with what has been previously obtained by the decomposition of certain fluorids by oxygen at a high temperature.

Aluminium, Silicium, &c. &c.—The experiments alluded to in my last communication are continued with zeal in the hope of producing aluminium in an economical manner. They have commenced by cheapening the production of sodium the present selling price of which in the large way has been reduced to 10 francs the kilogramme, (about 90 c. per lb.). We have already described in a preceding number the improvements which M. Deville has introduced into this manufacture.

Spongy Metals.-We have several times spoken of spongy metals and especially of the spongy iron of M. Chenot who first recognised the importance of employing aluminium as an alloy. He has for many years prepared specimens of very hard steel composed entirely of iron and aluminium-and which have received high commendation from most manufacturers. M. Chenot has often remarked, that in compressing spongy iron, the production of a harsh sound accompanied the rup ture of the moulds employed. Very recently in compressing spongy silicium this fact was reproduced in a very marked manner. Three grammes of silicium in the spongy state having been submitted to a pressure equal to 300 atmospheres, it exploded with a fearful noisethe fragments of steel from the broken matrix entered many millimetres into a plate of cast iron, and the body of the hydraulic press which was 20 centimeters in thickness was broken, and this, although the safety valve was open, thus showing the sudden violence of the shock. The action was entirely from above downward since no portion of the upper part of the compressed metal in this case suffered.

This phenomenon has analogies with the fact published by Mr. Gore in the Philosophical Magazine, namely, the explosive property of antimony when loosely arranged to favor its combination with chlorine under the influence of the pile. These facts open to us a new property of metallic substances, due to a particular mechanical state or condition. Possibly it is to this cause that we must refer the explosion so often noticed in the manufacture of potassium and sodium, the cause of which has never been explained, although chemists have frequently sought for it. Recalling the power of spongy platinum in the condensa tion of gases, we are led to enquire, if the phenomenon noticed by M. Chenot may not be of the same order. The spongy siliciuin previous to compression had been exposed to air, condensing in its pores a large volume of gas. The strong pressure, to which it was afterwards submitted, suddenly set at liberty the gas by diminishing the capacity of the pores, producing an explosive effect analogous to the sudden evolution of steam from water in the spheroidal state.

Paris Universal Exhibition.-The postponement of the opening of the French Exhibition to May 15, and then to June 1, has long been a recorded fact. It is not our place to describe what is going on in this great cosmopolitan palace, where nations are displaying their chefs d'œuvre. English astronomy will send forward a full size model of the great Greenwich circle executed under the direction of M. Airy at the expense of the British government. The telescopes of Lord Rosse, of M. Lassell, and of M. Nasmyth, will be represented also by models. Mr. Piazzi Smith will send certain astronomical instruments. The new observatory will transmit its complete collection of magnetic and me. teorological instruments which will be mounted and placed in action at Paris under the direction of Mr. Welch. The Bureau of Ordnance will exhibit the great theodolite which it has employed in triangulation, and examples of charts on different scales. The department of geological charts has also prepared a collection which will give a complete idea of its labors. The men of science in England at first felt some repugnance to exposing their physical instruments, like manufacturers, but this feeling has given way, and the number of exhibitors in this class will be a hundred or more, among whom appear, MM. Herschel, Brewster, Sabine, James, Willis, Lord Rosse, Wrottesly, Snow Harris, Wheatstone, Lassell, Grove, Warren de la Rue, Arnott, Gassiot, Brodie, and Frankland. Many of the great institutions figure also in the list, viz., University College, Guy's Hospital, &c. Every facility is offered for the exhibition of apparatus and machines in electricity which have not yet received a definite application. While the electric telegraph and telegraphic apparatus will be very severely scrutinized, being regarded as a matured subject, they will be extremely indulgent to machines for electrical motion, as this application stands in need of encouragement. Among machines of this class, will appear the motor apparatus described in this Journal, 1853, consisting of 4 equal electromagnets acting in succession upon 6 cylinderical armatures placed around the magnets which receive the current alternately by means of four circuit breakers: this apparatus is in active use in a machine shop in Paris, No. 10 Rue

*July, 1853, p. 110.

Bichat. A celebrated juggler, Robert Houdin, will exhibit an electrical pendulum in which he has surmounted two important difficulties, to wit, the disturbing influence of variations of current upon the motion of the pendulum, and the destructive influence of contact breakers. The construction of this pendulum has given to horology a new mechanism which will have important applications.

Photography.—Employment of the Cyanid of Iodine.—M. Stéphane Geoffray, Advocate at Roanne, and a great amateur in the art of photography, has employed with success the cyanid of iodine as the sensitive agent in direct positives. This compound he obtains by the action of iodine upon cyanid of mercury. It is very soluble in a solution prepared with wax and benzine, and gives to this coating a rapidity of action nearly equal to that obtained by the use of ceroleine. Applied to collodion in the proportion of other iodids, the cyanid uniformly af fords direct positive proofs of great beauty and which do not subsequently change. After fixation in the old bath of hyposulphite, the lights become very beautiful and are not inferior to those given by the use of the sesquichlorid of mercury.

M. Geoffray also employs the sesquichlorid of iron for all the purposes for which the sesquichlorid of mercury has been hitherto used, to bring out negative proofs on collodion and upon albumen in the manner employed for direct positives. He also employs this agent in place of the iodid to prepare sensitive papers for making positives in the shade and in a few seconds; according to the process of M. Blanquart-Ewrard. With this chlorid he also prepares a dry collodion of excellent quality, as follows:

To 100 grammes of ordinary non-sensitive collodion he adds 50 centigrammes of dry and finely pulverized perchlorid of iron, having no acid reaction; he boils it for a quarter of an hour, and adds four drops of tincture of iodine and filters the mixture. The glass being perfectly cleaned, he pours on the collodion, waits a moment to allow the coating to acquire a certain solidity-then plunges it in a bath of nitrate of silver, again in distilled water, and finally is dried, protected from the dust. The image is revealed as usual by pyrogallic acid.

This collodion is more sensitive than that prepared by using the protochlorids, but is much less so than the moist collodions.

Artificial Alcohol.-In my last communication I neglected to speak of the production of alcohol by means of water and illuminating gas. M. Berthelot has reached this important result through a species of contact between C4 H4 dissolved in fuming sulphuric acid and water contained in the acid. This important discovery has been the subject of a Report to the Academy of Sciences by M. Thénard. In this Report (a very flattering one to the young chemist) the venerable Dean of French chemists points out several other attempts of M. Berthelot and among them that of converting grape sugar into cane sugar. In spite of certain difficulties, we may still believe this possible result. Nevertheless M. Biot doubts the possibility of this change, because it requires that the intimate molecular structure of the substance should be changed, a change to which we have no analogy in the transformations hitherto made known. This difficulty however does not appear to MM. Thénard and Dumas as insurmountable; since in treating cane sugar

with an acid, its molecular constitution is changed so that its rotatory power over the polarized ray is reversed from right to left, why then should it be impossible to convert left-handed rotaton to right-handed?

Late changes in the scientific corps at Paris.—A considerable movement has taken place among the scientific men living in Paris-or who pass the larger part of their time in that city.

FAYE the astronomer and member of the Institute has been appointed Provost (recteur) to the Faculty of Sciences at Nancy. M. MALAGUTI has been made Dean of the Faculty of Sciences at Rennes. M. PASTEUR has been made Dean of the Faculty of Sciences at Lille. M. GoDRON, the author of the "Flore de France," has been nominated Dean of the Faculty of Sciences at Nancy. M. MORREN has been made Dean of the Faculty of Sciences at Marseilles. M. DESAINS has been appointed Professor of Physics to the Faculty of Sciences at Paris. M. FouCAULT has been nominated as Physicist to the Paris Observatory. M. LECOQ is made Professor of Botany at Clermont. M. LALLEMAND to be Professor of Physics at Rennes. M. FAVRE to be Professor of Chemistry at Marseilles. M. GERHARDT to be Professor of Chemistry at Strasburg. I may also add that the writer has been appointed Professor of Chemistry to the faculty of sciences at Nancy.

Bibliography.-Etudes physiologiques sur les animalcules des infusions végétales, comparés aux organes élémentaires des végétaux par M. PAUL LAURENT, professor à l'Ecole forestière de Nancy; grand in 4°, orné de 22 planches dessinées et lithographiées par l'auteur. New York, chez H. Bailliere.-The first volume of this work is now ready. This book contains the fruits of twenty years assiduous labor, and throws entirely new light upon the animalcules contained in vegetable infusions (infusoria); their origin and development and their habits are here exhibited in the most interesting manner. Through new methods (which he describes with care in his work), M. P. Laurent has been able to observe better than his predecessors, to group facts and phenomena which had previously escaped notice, and to reunite in one species individuals which have before been regarded as wholly distinct. This first volume has made a great sensation among micrographers, unhappily rare in France. The second and last volume will not be less curious.

Mecanique analytique, de Lagrange. 3d edition revised, corrected and annotated, by M. Bertrand; t. ii, Paris, Mallet-Bachelier.-We have already announced the publication of the first volume of this work. The second volume treats of Dynamics. It is concluded by several fragments either by Lagrange himself or his contemporaries.

Euvres Complétes de Fr. Arago, t. iv, containing the historical Eulogies of Malus, Gay-Lussac : the biographies of Copernicus, Tycho Brahe, Galileo, Newton, Kepler, Huyghens, Cassini, Lacaille, Roemer and a great number of other astronomers and physicists.