tures at the Faculty of Sciences of Paris, and the Museum of Natural History. In one of these instruments, made for anatomical demonstrations, two persons may see at once the same object. The two images are formed by a prism whose transverse section is an equilateral triangle, which is placed immediately below the objective in such a way that its edge shall be perpendicular to the optic axes of the lenses. Each of the two faces of the prism reflect the image of the object at such an angle of incidence that this image passes at right angles to the surface opposed; finally the ray of light, thus turned from its direct course, meets a second prism whose surfaces are parallel to the first, but whose edges form with the edges of that a right angle. The image reversed behind the objective is thus righted by the first prism, so that the observer can direct his needles towards any part of the object without difficulty.

In other microscopes, three or even four images are obtained through as many ocular tubes, by substituting for the ordinary prism below the objective, either three reflecting prisms placed around the optical focus of the instrument, or a quadrangular prism acting as a multiplying prism. The loss of light from these additions is less than would be supposed, and Milne Edwards and other micrographers say that such instruments have been very useful in their demonstrations.

Aluminium and the Alkaline Metals.-The persevering efforts of M. H. Sainte Claire Deville and M. Bunsen, lead us to hope that aluminium will soon become a useful metal. The last advance has been made by means of the pile causing it to act on chlorid of aluminium. It is an important step; but still the process is expensive. Deville, not expecting to reach a cheaper method by means of the galvanic battery, has endeavored to use the old method by sodium, and has sought to reduce the cost of preparing this last metal. He can now prepare this metal at a cost of 25 francs the kilogramme ($2 15 cts. the pound avoirdupois.) The following is the process:-Mix together for a thousand parts,

Dried carbonate of soda,
Carbonate of lime,

Pulverized charcoal,

714 parts.

108 66

178 66

Reduce the whole to a paste with oil, and put it into an iron retort, like that of a mercury bottle. A musket barrel two decimeters long is fitted to the extremity, to which is adapted one of Donny and Mareska's receiving vessels. The retort and barrel are heated to redness: the sodium is immediately reduced, volatilizes, and is condensed in the recipient.

The only peculiarity of this process is the carbonate of lime, which serves to prevent the mixture from entering into fusion: it was through a perusal of the memoir of MM. Donny and Mareska, remarking that these chemists recommend the use of crude tartar which contains lime, that Deville was induced to study out the reason for this preference; he soon discovered it, and proved that he was right, by adding to the ordinary mixture 15 per cent. of chalk.

M. Deville has also prepared metallic chromium, by using the method mentioned in a preceding number of this Journal, and which depends on producing a very high temperature in an ordinary furnace. The

mixture employed is oxyd of chrome and carbon, the former in slight excess. The metallic chromium resulting was of extraordinary hardness; it scratches glass like the diamond.

Manufacture of Alcohol.-The disease of the vine and the consequent dearness of wine, has directed attention to different methods of obtaining alcohol without the aid of the grape, or the cereal grains, which last the French government protects, as their use diminishes the amount of food and raises prices. Recourse has been had to the juice of the beet, which has given rise to an extensive establishment under M. Leplay, to which I alluded in a former note on the sugar of barytes. But as this use of the beet is at the expense of the sugar, and would finally turn the sugar manufactories into distilleries, we now hear of the alcohol of Indian corn, alcohol of couch grass ("chiendent"), alcohol of asphodel, which have begun to be manufactured in the colony of Algiers. Quite recently, M. Arnoult has applied to the same purpose the fact discovered by M. Braconnot of Nancy, and which consists in transforming wood into sugar by means of sulphuric acid. M. Arnoult has observed that poplar wood gives the best results, affording 79 to 80 per cent. of sugar to be converted into alcohol. The wood is reduced to coarse saw-dust then dried at 100° C; after cooling sulphuric acid is added in small portions, taking care that the material does not become heated. It is well mixed, and after repose for 12 hours, it is triturated until the mass, before almost dry, becomes quite liquid so as to run. This liquid, diluted with water, is made to boil; the acid is saturated with chalk, and the liquor after filtration is subjected to fermentation; when the alcohol is distilled off by the usual process.

The quantity of sulphuric acid employed should not be less than 110 parts for 100 by weight of the dry wood. The author hopes to diminish the quantity of acid, and is engaged at this time on this part of the process. We cannot say that the process will be economical.

Crystallizations.-We have just seen at the Sorbonne, in the laboratory of M. Dumas, a magnificent collection of artificial crystals. The principal types of crystallized compounds are represented among them, and the crystals are of high finish and transparency. Artificial crystals are usually imperfect on one side; but the author of this collection has obtained crystals that are wholly without defects. There are transparent crystals of hyposulphite of lime of perfect symmetry; of the double sulphates, monoclinic in form, of the magnesia series SO3RO+SO KO+6HO; the different alums; the double chlorids; the different salts of copper with the fatty acids of the homologous series CaKO, &c. &c. The owner of this fine collection is a German chemist, M. Stephany, who gives his time and labors wholly to this business and who devotes himself to his crystallizations with a patience quite Germanic. M. Dumas employs him in his laboratory and has given him a commission to form a collection of the principal artificial crystals an example which should be followed. Now that crystal. lography has become a part of chemistry, it is indispensable that artificial products should be studied with the care which mineralogists have devoted to native crystals. The many misunderstandings will be avoided when the forms shall have been referred to types whose exact composition is known, and whose crystallized form can be verified.

This undertaking is specially interesting for scientific instruction in France, since the new programme of Chemistry which has just been prescribed to the Professors of the Faculty of Science, contains questions relating to isomorphism, polymorphism, isomeromorphism, and in general all that relates to the relations between chemical composition and crystalline form.

Introduction into France of a new species of Silkworm.-The "Société Zoologique d'Acclimatation," alluded to in a former communication, is highly prosperous. It has made numerous laudable attempts to acclimate useful animals from different parts of the globe, and to domesticate wild animals. Although too recently formed to pronounce on the full success of its endeavors, it is already in possession of facts which give great hopes. Of these, is the acclimation of the Bombyx Cynthia (" chenille du ricin") a silkworm of India, which, according to Roxburgh, furnishes a silk so firm that clothes made of it will last a life time. The honor of having introduced this Bombyx belongs to M. Milne Edwards, the Dean of the Faculty of Sciences of Paris, who has made experiments also on the hatching of the eggs of these silkworms.

The

As the Ricinus (Castor-oil plant) grows with wonderful facility in the south of France and Algiers, attempts have been made for a long time to introduce the Bombyx Cynthia. But the rapidity with which the eggs hatch, and the short duration of the period of the cocoon state, has seemed to render it difficult to carry the animal from India to Europe. A series of circumstances has led to a triumph over the difficulties, and some decisive trials place the success beyond doubt. cocoons have a russet color. At one extremity there is an opening which the caterpillar reserves in order to facilitate its escape on passing to the butterfly state. The threads of the cocoons are so agglutinated that at first it seemed impossible to divide them; but M. Guerin Menneville has succeeded in proving the dividing possible after boiling the cocoons in alkaline water. There are experiments now in progress at Algiers, to ascertain the value of the silk per acre of Ricinus compared with that of an acre of mulberry.

Industry and Agriculture of Algeria.-We cite some facts from an interesting report made by Marshall Vaillant, Minister of War, on the agricultural and industrial condition of our French colony of Algeria

in 1853.

Fertility of Algeria.-In 1853, Algeria furnished to France over a million hectoliters (over three millions of bushels) of cereal grains, valued at fourteen millions of francs. It has produced the tender wheat ("blé tendre") of the best quality weighing 86 to 88 kilograms in place of 76.

Industry in Silk.-The superior quality of the Algiers silk, attested by two medals at the London exhibition and by the price it brings at Lyons, leaves no doubt that Algeria must take a prominent place among countries which derive their principal wealth from the production of silk. In 1853, three hundred and thirty-five persons ("éducateurs") have collected in the single department of Algiers 14,000 kilograms of cocoons. Plantations of mulberry are daily multiplying and the silk industry is constantly increasing.

* This Journal, vol. xvii, page 414.

Cultivation of Madder.-The madder of Algiers is known to be more highly esteemed than that of Cyprus. It follows from calculations made from several columns that the cost is 70 francs the 100 kil., while it brings 140 to 155 francs.

Cochineal. The success of the cochineal insect at Algiers is no longer doubtful. A hectar planted with 13,000 feet of cactus gave a crude product of 10 to 12 thousand francs of which only 2000 should be set down for expenses: there are actually 29 "nopaleries" (plantations of cactus) and 500,000 feet of cactus.

Cultivation of Cotton.-The cotton of Algiers took 11 prizes at the London Exhibition. The two varieties which grow best at Algiers are those which are of the highest price, (because America can furnish only 30,000 bales [?]) and also which give the largest return. Europeans and Arabs are engaged in the work, and during a single year the plantations of cotton have increased ten-fold.

Oils.-The olive tree in Algeria grows to the height of our largest forest trees. Certain countries, and especially Kabylia, are covered with it. Since 1852 the commerce in oil has rapidly increased. Europeans have put up well managed establishments among the mountains, and students in our nurseries from among the native population are taking lessons in grafting the olive trees. In 1853, although the product was below the mean, the amount exported was 2,914,430 kilog. Government Nurseries.-The objects of the government nurseries are to produce a large number of young trees and give them to the colonists at a small price, and experiment on the cultivation of exotic industrial plants and endeavor to acclimate them in Algiers. To them we owe the cultivation of cotton, madder, the trades in cochineal and silk; and probably also the acclimating of the coffee and tea plants. Through them the oases have received the rice of China, which grows at the foot of the palms without requiring special care.

Value of the Forests.-The forest country of Algeria as now known, comprises about 1,200,000 hectars. Species of Cork Oak constitute a large part of these forests, and already 12,000 hectars of this wood have been explored. On the line of the Tell there are forests of cedar some of which are 4 or 5 meters in circumference; there is good timber for the construction of ships, and also other kinds, like the pine, juniper, arbor vitæ, olive, black walnut, etc., which do not yield in quality to the trees of America.

Metallurgical and Mineralogical Industry.-The exploration of the mines of copper have been active in consequence of a temporary permission of exportation given to foreigners. There were exported 3,111,516 kilog. of argentiferous lead ore. Some furnaces established within a few years produce steel rivalling that of Sweden. Quarries of marble and translucent onyx are opened which still bear marks of the labors of the Romans.

Coral Fishery.-One hundred and fifty-six vessels in the coral fishery explored in 1853 the vicinity of Bone and Calle and collected on an average 230 kilograms per boat. At the price of 60 francs per kilogram, the value of the fishery was 2,152,800 francs. Large banks have recently been discovered on the coasts of the Province of Oren.

We stop here with our citations. The rest of the Report refers espe cially to commerce, administration and war.

SCIENTIFIC INTELLIGENCE.

I. CHEMISTRY AND PHYSICS.

1. On the influence of the direction of transmission upon the passage of radiant heat through crystals.-KNOBLAUCH has published the second portion of his very elaborate and skillful investigation of this interesting subject. We shall give his results in his own words.

I. Radiant heat penetrates certain crystals of the optically biaxial systems, like Dichroite, Topaz, Diopside, &c., in different quantities in different directions. It passes, for instance, most freely through dichroite in the direction of the middle line, less freely in a direction perpendicular to the plane of the optic axes, and least freely of all in a direction parallel to the supplementary line. In blue topaz, on the contrary, it passes in the smallest proportion in the direction of the middle line, more abundantly perpendicular to the plane of the optic axes and most freely in the direction of the supplementary line. After this transmission the rays of heat, according to their direction within the crystal, exhibit different properties in their behavior for example toward diathermanous bodies. In this particular different crystals exhibit different peculiarities.

In the case of polarized heat, differences may appear for one and the same direction according to the position of the plane of polarization. Thus rays of heat whose plane of polarization coincides with the plane of the optic axes penetrate yellow and blue topaz more abundantly parallel to the middle line than those whose plane of polarization is at right angles to the plane of the axes, whereas precisely the contrary is the case in Heavy Spar, Hornblende, Pistacite, Mica, Dichroite, &c.

Rays of heat polarized in different planes often differ from each other in their capacity to penetrate diathermanous bodies after their passage through the crystal. The comparison of the rays polarized in the same sense and transmitted in the same direction exhibits the greatest variety, not only in different crystals but even in those belonging to the same species, as yellow and blue topaz, &c.

In one and the same substance, as for example mica, the quantitative as well as the qualitative differences of the rays polarized in different planes increase with the thickness of the layers penetrated.

When the heat passes successively through two plates of the same crystal, e. g. Pistacite, phenomena are observed analogous to those already mentioned according as the planes of the optic axes coincide or are crossed.

II. When the rays of heat pass through certain crystals of the optically uniaxial systems, as amethyst, idocrase, &c., quantitative as well as qualitative differences are exhibited according as the rays penetrate the crystal in one or another direction.

However great these differences are in the cases of transmission parallel and perpendicular to the axis, no difference of any kind is perceptible in the behavior of rays of heat which, whatever may be their directions, are all transmitted at right angles to the axis.