Mubarak, Minister of Worship at that time. This decree directed that a building be erected in the ministerial premises, of a capacity for the proper accommodation of 30,000 volumes, in which should be collected and preserved the books, maps, scientific instruments, and papers, belonging to the public benevolent institutions and public offices of the country, in such a shape as to be convenient for the use of the public. The library will include the "Old Library," founded by Mehemet Ali in 1838, consisting principally of works printed at the public printing-office. Of the libraries of the public benevolent and religious institutions to be incorporated in it, a writer in the Allgemeine Zeitung names as known to him those of thirty-one mosques, three Talijne, or dervis cloisters, one school, and three private residences, containing in all 16,562 volumes, exclusive of the collection in the mosque of Al Azhar. The library will be made as complete as possible in the special departments of Egyptology," of which all works published, in all languages, will be procured, and of Oriental literature. The collection of Arabic works will be carefully looked to, and it is anticipated that this department of the library of many valuable writings, now practically out of the reach of European scholars, will be made accessible and useful. It is intended also, in the scientific departments, to provide the works necessary for the pursuit of the professional studies of engineers, architects, and others, to professional men, without their having to go out of the country. The library is open to every one for consultation, on the single condition of his presenting a certificate signed by his consul or some prominent man of the city; but books cannot be taken out. The collection has already become very valuable. During 1876 it was enriched by the addition of a large portion of the works, chiefly Oriental manuscripts, of the late Mustafa Fazyl Pasha, of Constantinople.

The Assembly of the Delegates of Egypt was opened on the 23d of November. The Khedive recommended the establishment of an Egyptian national bank.

The war with Abyssinia, commenced in 1875, continued through the greater part of 1876, being in its results rather disastrous to the Egyptians. (See ABYSSINIA.)

EHRENBERG, CHRISTIAN GOTTFRIED, a German naturalist, born April 19, 1795; died June 27, 1876. He entered the University of Leipsic in 1815, studying at first theology, and then devoting himself to the study of the natural sciences and of medicine. In 1816 he went to Berlin, where he graduated as doctor of medicine in 1818. In the following year the Academy of Sciences furnished him and his friend Friedrich Wilhelm Hemprich with the means for a long scientific journey. They went to Egypt and its neighboring countries, from which Ehrenberg returned alone in 1826, Hemprich having died at Massowah. Upon

his return to Berlin he was appointed extraordinary professor in the university, and in the following year he was created a member of the Academy. In 1829 he took part in Alexander von Humboldt's journey to Asia. Having become Secretary of the Academy in 1842, he was appointed ordinary professor at the university in 1847. A sketch of his first journey is contained in "Naturgeschichtliche Reisen durch Nordafrika und Westasien in den Jahren 1820-25, von Hemprich und Ehrenberg." The scientific results of this journey are contained in "Symbolæ physicæ seu Icones et Descriptiones Mammalium" (1828'33), "Symbolæ physicæ Avium (1828), "Symbolæ physica Insectorum (1829-'34), and "Symbolæ physicæ Animalium Evertebratorum sepositis Insectis" (1829-'31). His great scientific fame is based chiefly on the knowledge of microscopic organisms, which was considerably promoted by him. Although his observations have been superseded by more recent ones, he must be regarded as the founder of this school. Among his works pertaining to this subject the most important are: “Organisation, Systematik und geographisches Verhältniss der Infusionsthierchen " (1830), “Zur Kenntniss der Organisation in der Richtung des kleinsten Raums (1832-'34), "Zusätze Erkenntniss grosser Organisation im kleinen Raum " (1836), and his principal work, "Die Infusionsthierchen als vollkommene Organismen, ein Blick in das tiefere Leben der organischen Natur" (1838), with 64 copperplates engraved from his own drawings. He was led by the discovery that many firestones, chalk, and other mineral substances consisted of layers of microscopic organisms, to the observation of the smallest fossil creatures. On these researches he reported in “Die Bildung der europäischen, libyschen und uralischen Kreidefelsen und des Kreidemergels aus mikroskopischen Organismen" (1839), "Die fossilen Infusorien und die lebendige Dammerde" (1837), and his principal work on this subject, "Mikrogeologie" (1854). Among his later works are: "Uebersicht der seit 1847 fortgesetzten Untersuchungen über das von der Atmosphäre unsichtbar getragene reiche organische Leben" (1871), "Nachtrag zur Uebersicht der organischen Atmosphärilien (1872), and " Mikrogeologische Studien über das kleinste Leben der Meerestiefgründe aller Zonen" (1873).

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ELECTRICITY. Electricity and the Theory of Comets. Reitlinger and Urbanitsky have addressed to the Paris Academy of Sciences a memoir on a new electrical repulsion and its application to the theory of comets. It is known that the luminous column produced in a Geissler tube gives rise to a phenomenon of attraction, when the finger or any conductor whatever is brought near the tube. The authors experimented with two tubes that had contained, the one bromine and the other perchloride of tin. The light

obtained was greenish and of peculiar aspect, in which the spectroscope showed neither the rays of bromine nor those of tin perchloride, but only the three well-known bands usually attributed to the spectrum of carbon. These bands are the same which Vogel and other observers have designated as forming the spectrum of comets. Besides, the luminous column thus produced gave rise, not to a phenomenon of attraction, but to a very welldefined repulsion. The authors, after repeated experiments, are firmly convinced that these curious phenomena are due to the extreme rarefaction of the gases employed; and, since the gas forming the tails of comets is undoubtedly in a state of high rarefaction, they conclude that this is the cause of the repulsion of the sun on the comet's tail, the sun being then considered simply as a good Electrical Phenomena in Plants.—The leaf of the plant Dionaea muscipula, one of the carnivorous plants, has been found by Dr. Burdon-Sanderson to possess an electro-motive action. The same author has shown that when contraction takes place in the leaf there is a negative variation of the current; he has also observed in the leaf something corresponding to the latent stimulation of muscles and the electrotonus of nerves. This subject has lately been investigated by Hermann Munk, whose results have been published in Der Naturforscher. Briefly they may be stated as follows:

conductor.

Applying the unpolarizable electrodes to the under surface of a leaf, a current appears in (say) an upward direction, i. e., flowing in the leaf from the end of the petiole or leaf-stalk (call it the fore-end of the leaf) to the free end or point of the leaf (which may be called the hinder end). Points situated similarly on the two halves of the leaf are homogeneous, hence on the two sides of the midrib all is symmetrical. Conceive the midrib divided into two unequal parts, a shorter hinder part and a longer fore part; then in each of these parts every point nearer the inner end is positive to every more distant point. The most positive point of the midrib lies about the fore-end of its hindermost third, and with increasing distance from this point the positivity decreases toward both ends.

Suppose lines drawn on the surface of a half-leaf at right angles to the midrib; and call these crosslines of the leaf. Every point of such a cross-line proves negative to the corresponding point of the midrib; and regularly the negativity of these points increases first to a maximum, and then, on to the outer leaf-border, decreases. The most negative point of the cross-line never coincides with the middle of the line, but is always nearer the leaf-border than the midrib.

By connecting the most negative points of all the sections, we have a principal line of length nearly parallel to that of the midrib. All points in this line are homogeneous. So also are related points of other lines of length running parallel to the midrib, and lying inward from the principal lengthline. Of the middle parts of two cross-lines, which are both in the fore or both in the hinder halves of the leaf-halves the middle nearer to the fore or to the binder leaf-border respectively is always positive to the more distant middle, and the force, downward in the former case, upward in the latter, in

creases with the width of span of the arch. The principal length-line, then, is the sum of the most tion is the most positive point of the leaf at the negative points of each leaf-half, while in opposifore-end of the hindermost third of the midrib. And, as in the whole leaf all is symmetrical on the two sides of the midrib, so in each leaf-half all is symmetrical on the two sides of the middle crossline. The complete symmetry of the leaf seems to be disturbed only in that the most positive point in the midrib is displaced back from the middle. The examination of the upper surface of the leaf offers great difficulties, owing to its sensitiveness. These having been overcome, it is found that the same distribution of tensions prevails as on the under surface.

The source of the electro-motive action he

supposes to reside in the interior of the leaf, nor can it, according to him, arise from heterogeneity of surface. The primary organs of the hairs, the fibro-vascular cords, nor the epiderelectric forces are neither the disk-glands, the mis, but the cylindrical cells of the parenchyma in the halves of the leaf and in the midrib. kind that the positive electricity is driven from the middle of the cell to each of the two poles, which are positive poles to the middle.

These cells are endowed with forces of such a

The mechanical movements of the plant are of two kinds: stimulation movements, and resorption movements. In the former, the leaf closes very quickly after stimulation, within a minute or so, all parts moving simultaneously. In a few hours it begins to open again, and is quite open after twentyfour to thirty-six hours. It is then susceptible of further stimulation. The resorption movement, on the other hand, is more rare, and occurs when a small piece of flesh, albumen, or the like, is carefully laid on the leaf-surface, avoiding the sensitive hairs. The closure which follows is very slow, not beginning for some hours, and being completed only in one to two days. The movements of the two halves are irregular and unsimultaneous, and depend on the place of contact, from which they spread outward. The reopening begins after several days, and takes several days to be completed; and during this time the leaf is not, or is very little, susceptible of either stimulation or resorption movements. The leaf may die after one such resorption movement, and two or three always prove fatal to it; it opens

no more.

We now come to the electrical phenomena in stimulation, of which Dr. Sanderson said that they presented a negative variation similar to that of the muscle-current. The electrodes were placed on the under surface of the midrib, as being the only part of the leaf which, during movement of the latter, does not alter in position. On stimulation through movement of the sensitive hair, there occurs, not a simple negative variation, but, as the author expresses it, a positive variation with negative primary impulse, which he calls double variation. electrical phenomenon occurs even when, notwithstanding stimulation, there is no movement of the leaf. The latter circumstance renders possible an examination also of the leaf parenchyma; and the same double variation is here observed.

This

As to the explanation of this double variation, the supposition that all the cells pass first through a negative, then through a positive variation, is to be rejected; the process is rather (the author thinks) that through stimulation the cells of the upper halves of the half-leaf parenchyma and of the upper midrib parenchyma experience a negative variation, those of the under halves of the half-leaf parenchy ma and of the under midrib parenchyma a positive; that is, the negativity of the middle of the cells to

strengths of current employed. Since, however, the increase of magnetism from the second last to the last observation, in cobalt, was much greater than in nickel, it is not impossible that, with very strong electric currents, the magnetism of cobalt may be greater than that of nickel. Unlike the nickel, the cobalt piece was not without coercive force.

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New Electro-Motor. In a new electromotor recently exhibited in London by its inventor, Chutaux, the primary force is supplied by a battery of eight or more cells, being a modification of the Bunsen battery. The elements used are graphite and unamalgamated zinc, and the exciting fluids are sulphuric acid and bichromate of potash in the inner (or graphite) cell, and a solution of acid sulphate or bisulphate of potash in the outer (zinc) cell. No material action is exerted on the zinc while the battery is at rest, hence the reason for dispensing with the process of amalgamation. Two or more horseshoe electromagnets, with their poles upward, are worked by the current, a wheel rotating on an horizontal axis immediately above and almost touching them. This wheel is practically formed of two parallel wheels joined at their circumference by a series of soft-iron bars. As soon as the current is set up the wheel begins to revolve, owing to the attraction between the electro-magnets and the iron, the motion being kept up, and rapidly increased, by means of a simple automatic "current-reverser." principal feature to which the inventor draws attention is the construction of the transverse soft-iron bars, each of which is composed of seven thin plates, much being thus gained in intensity of magnetization, and consequently in mechanical power. By a series of ingenious devices the machine is applied to the working of pumps, sewing-machines, lathes, etc., as a substitute for manual or foot labor. It is not of course in any way intended to supersede steam, its object being the simple and easy performance of labor of a light description. The battery is free from smell, and, being very “constant," will last for a long time without renewal, the trouble involved in starting and stopping the machine being practically nil.

The

Influence of the Electric Current on the Dimensions of Iron.-The change in length of a conductor, through which an electric current is passing, has been measured by Exner, whose method is free from the error caused by the expansion due to the heat produced by the current. In making this measurement, two pieces of the same wire of nearly equal lengths were hung one over the other, and so connected with a battery that the current might be passed through either. The lower wire was passed through a glass which might be filled with water if desired. The elongation was measured by resting the end of the wire on a lever carrying a mirror whose deflection was read by a microscope and scale. The current being passed successively through the two

wires, a different deflection was obtained in each case, but these were rendered equal by inserting an additional resistance in circuit with that wire whose elongation was greater. The tube was now filled with water so as to carry off the heat generated in the lower wire as rapidly as possible. It was found that the galvanic expansion was only 1.2 to 2.2 per cent. of the heat-expansion; and no connection was recognizable with the nature of the metal employed. If it be considered that these values, of course, can only be an upper limit, it will follow, from the smallness of the effect obtained, that there is no sufficient ground for the hypothesis of a special expansion power of the galvanic current. There can hardly be any doubt that the slight expansion which the water-inclosed wire still shows is simply and alone due to the heat remaining in it.

Magnetic Equivalent of Heat.-In Lamin and Roger's decisive experiment establishing the production of heat through disappearance of magnetism, the soft iron of an electro-magnet was placed in the reservoir of a large thermometer of oil of turpentine; on sending an interrupted current through the spiral, it was observed that the liquid expanded. The conclusion hence drawn was, that during each magnetization a part of the electricity goes into the iron, producing magnetism, and that at the moment of demagnetization this magnetism is transformed into heat. In further investigating this subject, Cazin employed three different methods of experimentation. In the first, the iron core was inclosed in an hermetically-closed vessel filled with petroleum, and surrounded by the magnetizing spiral. From the vessel proceeded a capillary tube, also containing petroleum, and the changes of level in it were observed when the core was magnetized by an interrupted current. But inasmuch as change of level might arise, not from heat-action, but from the expansion of the iron by magnetism, the following experiment was arranged:

Into the vessel containing the liquid and the iron core were introduced some closed glass tubes, which displaced a third of the liquid; the vessel was then closed, and the experiment repeated. If the expansion of the iron were the cause of the change of level, this must now be the same as in the experiment without the glass tubes; if, on the other hand, the change of the level were due to the heat produced, it must now be different, for, instead of three volumes glass were heated by the same quantity of heat. of liquid, two volumes of liquid and one volume of The experiment then revealed a difference, which corresponded to the difference of the specific heats and confinements of expansion of petroleum-oil and glass.

It was thus proved that the discontinuous magnetization of an iron core produces heat. In another method for demonstrating and measuring this heat-effect, the core was an iron tube, closed at both ends with corks, and inclosing the bulb of a common thermometer. Here, again, there was heat-action when the spiral was traversed by an interrupted cur

rent. In the third method a differential thermometer was used, consisting of two hollow iron cores, communicating by a capillary tube in which was a liquid index: every heat-action in the one core was followed by an expansion of the contained air, and displacement of the index.

In order to determine the cause of the development of heat, M. Cazin proceeded as follows:

Round the iron core in the petroleum thermometer two coils of 480 turns were passed, one of them being in the interrupted magnetizing circuit, while the other formed a special circuit, which at each turn of the interrupting apparatus was closed. The first coil could now induce a current in the second, if the closures of the two circuits took place at the proper times, as might be arranged at will. These experiments gave the greatest development of heat when the circuit of the second spiral remained continually open. The heat was not altered when the circuit was closed at closing of the magnetizing current. There is thus no thermal action during the variable period of closure. Lastly, the heat was smaller when the circuit of the second spiral, during the opening of the inducing circuit, was closed; it went down as much as the half. "It thus proved that the production of the magnetic heat takes place during the opening of the voltaic circuit; consequently, that it accompanies the disappearance of magnetism in the core.'

The decrease of heat in this last case is explained on the principle of thermo-dynamics. The disappearance of the magnetism is the cause of the appearance of a certain quantity of heat. When no circuit is near, in which an induced current can arise, then the whole of this heat appears in the core; but, when induction occurs, a part of the heat appears in the induced circuit, and the rest remains in the core. The cessation of the magnetization is an operation in which the magnetic energy decreases and is transformed into heat-energy, either in the core or in the neighboring masses which are in a position to be the seat of induction phenomena.

Improved Electric Railway-Signal.-A simple and effective application of electricity to railroad signaling is in use on the Boston, Lowell & Nashua Railroad. The apparatus is described and illustrated with a woodcut in the Scientific American. Its principle will be readily understood from what follows: A single-cell Calland battery is connected to the two rails at one end of a given section of the line (say two miles in length), each section being insulated from adjoining sections. At the other end of the section the signal has an electromagnet similarly connected to the two rails. When the circuit is closed, as is normally the case, the magnet is excited and the signal controlled thereby, so as to show that the line is clear. But when a train enters on the section, then a shorter circuit is made by the wheels and axles, and the current returns to the battery by this course instead of passing through the signals. The magnet ceases now to attract, and the signal, by mechanical means, is at once turned to indicate danger. It is ob

vious that this must occur as long as a single car remains on the track, or when the circuit is broken by a displaced or broken rail, or any other cause. Hence the device may be applied over an entire line, and will indicate the condition of every section to a train about to enter on the same. It is not affected by changes of

weather.

ELIO, JOAQUIN, a Spanish general, died in January, 1876, very much advanced in years. He was educated for service in the royalist army in Spain, in which he obtained his first commission. During the progress of a stormy public career, he served under many governments. In 1860 he commanded a part of the Carlist insurgents, and during the last Carlist War he also acted with Don Carlos, by whom he had been threatened with the loss of his command, and with court-martial, on several occasions. In 1860 he was captured by Queen Isabella's forces, and was only saved from death by the clemency of the Queen. On that occasion, he wrote a letter to the Queen, in which he promised never again to take part in any movements against her; but, nevertheless, he fought in the Carlist War against her son, Don Alfonso. Don Carlos appointed him in 1873 captain-general of the Carlist forces, and Minister of War. He conducted the operations of the Carlist forces against Bilbao, and the defense of the line of Sommorastra, in 1874, and, when the Carlists were repulsed there, he resigned his position, but remained with the army.

ENGINEERING. The art of engineering has made great strides in late times, and, with the growth of commerce, has been put more and more into requisition to devise and construct shorter and easier avenues of communication. In all progressive countries gigantic works are constantly in progress, requiring millions of outlay and years of labor, while still greater undertakings are being seriously proposed, such as would formerly have been considered fond and idle dreams. Among them may be mentioned the connection of the Black Sea with the Caspian by a ship-canal; the construction of an artificial channel between the great rivers of Central Africa, so as to make a navigable water-way across the continent; the cutting of a passage between the sea and the low bed of the great African Desert, by which a great portion of the sandy waste would be submerged, and wide districts rendered fertile; the building of a great shipcanal through Southern France from the bay of Biscay to the Mediterranean; the widening and deepening of the Seine, so as to make Paris a seaport.

It is worthy of note that the chief engineering projects of the most recent times look toward the extension and improvement of water-communication. The construction of a ship-canal through the American Isthmus, which has long been a cherished project of the American people, may be said to be on the