of 4.9 per cent., to 19.47 in the scale. In conclusion, the authors state that they find no alloy of copper which conducts electricity better than pure copper; and they call the attention of experimenters to the importance of stating in future determinations whether the wires they employ are hard drawn or annealed, and at what temperature the observations are made. A more full abstract of the paper appears in the "Jour. of the Franklin Inst.," for May, 1862. Electric Lights for Lighthouses.—Mr. J. K. Whilldin, C. E., communicates to the journal just quoted (April, 1862), an article relative to Prof. Way's electric light, with mercury, and to the arrangements for projecting lights generally. Before entering upon the topics treated of by him, it may be remarked that the introduction of the electric light for lighthouse purposes appears to have been directly owing to the demonstrations by Prof. Faraday, in connection with Prof. F. H. Holmes, of the practicability of its use, and especially to the experimental exhibition of its capabilities in the South Foreland lighthouse, near Dover. The electric light is obtained by heating to incandescence, by means of the passage of an electric current between or through the bodies so employed, carbon points, which are made to terminate the positive and negative conducting wires of a battery, or a slender filament of some metal introduced between the ends of the wires. In the former case incandescence of the points can be produced only when these are brought very close together, but usually not into positive contact; in the latter, the light is the result of the intense heating of the fine wire owing to the low conducting power it possesses for the current. In either case, a current of very high intensity is usually required; and this may be obtained either from a galvanic battery of many cells, say from 40 to 100, or from the magneto-electric machine. The suffocating nitrous fumes generated during action of a Bunsen's battery, and indeed, the expense of materials and the attention required in order with any form of battery to maintain a regular and intense current, constitute serious objections to their employment. Prof. Faraday gave preference to the electro-magnetic machine, as being both a less troublesome and a more economical source of electricity than any galvanic battery. At the present time both are, in different places, in use. The current of the electro-magnetic machine is instantly produced upon giving a rotary movement to the mechanism, regular while the movement is kept up, and at once discontinued, without waste, when it ceases. Its use thus involves the addition of some motive power; so that where a steam engine is required for other purposes, this mode of producing the current is readily and inexpensively resorted to. Where such an engine is not present, Mr. Whilldin suggests the economy and advantage of Erics son's hot-air engine. Mr. Whilldin calls attention to the great cost of the Fresnel lenses now generally employed for projecting the lights, of whatever kind; those of the first order, as at Cape May, Hatte ras, &c., 6 ft. diameter by 9 ft. high, costing from $5,000 to $11,000. By employment of the electric light he judges that for these an appara tus not costing more than $400 to $500 can be substituted. Faraday, indeed, states that all the light from an electric lamp could be utilized within a space not exceeding the size of an ordinary hat, a result that, if practicable, would reduce the cost yet mare. The difference and saving arise mainly from the diminution allowed in the size of the very costly lens arrangements, as the electric light is produced almost at å point; while to augment the intensity and pene trating power of the common oil lights, the number of the burners and the space occupied by the flame must be very greatly increased. With the electric light, increase of brilliancy involves increase of battery power, and so of expense in this way, but with no enlargement or inconvenience in respect to the lenses. The electric light hitherto most commonly employed for lighthouses, has been that of the carbon points. In this system the difficulties practically encountered have been chiefly those of obtaining the carbons sufficiently free from impurities and variations of compactness to preserve a uniform current and brightness, and so to maintain the proximity of the points by clockwork or other automatic mechanism during their slow but continued waste, as to prevent interruptions of the current from this source, either through too great distance or absolute continuity of the carbon electrodes. Prof. Holmes' magneto-electric light, however, with carbon points, appears from evidence in a late parliamentary report to have been successfully used in the South Foreland lighthouse, England, during a period of 6 consecutive months. In France, also, magneto-electric lights are in successful use; and though there the system is peculiar in the respect of continually reversing the current, no important difference in the two lights has been detected. By means of dark glass, Prof. Faraday compared the electric light with that of the sun: the latter was not at the time at its brightest, but the intensities of the two lights were about equal. He says that the eyes of the keepers of the South Foreland light are not affected,though protected by blue glasses of very pale color; but that they judge better of the light by observing the place and intensity of the rays within the lantern, than by looking at the light itself. In some experiments on lights in France, the intensities of an argand burner and of the electric light were found with approximate correctness to be as 1 and 94; and that of the "first-order flash" of the former being 80 to 90, that of the "cast-glass flash" of the latter was placed at 55,000, and of the "first-order flash" at 220,000. The electric light is particularly valuable for its power to penetrate a thick, hazy atmosphere; and sailors on board steamers have declared that in such weather Prof. Holmes' light is seen 7 miles farther than any of the ordinary sorts. A practical difficulty at the same time growing out of the great intensity of the light, is said to be that navigators cannot readily judge of the distance of the shore or point from which the light proceeds. 6 Prof. Potter, of London, is led by extensive photometric experiments to question the superiority of the dioptric system over reflectors; in other words, to doubt the advantages claimed for the Fresnel lenses. He finds that in passing through 2 inches of clear flint glass with highly polished surfaces, about of the light is still lost by reflection and absorption; while ordinary good looking-glass reflects from to of the incident light, and highly polished speculum metal still more. Faraday considers that the dioptric apparatus absorbs not less than 50 per cent., while pure polished silver reflects .95 of the total incident light. Sir J. F. W. Herschel has recently proposed an improved reflector, which is expected to prove a great economizer of light. In this, he would render available Liebig's recent discovery of the means of precipitating pure silver from its solution, contained in a thin shell of glass: the silver, protected from all agencies that would tarnish it, is said to reflect.91 of the light impinging on it. It is proposed to use mirrors of this sort, and in forms intended to prevent the partial dispersion and waste of light which occur with the parabolic reflector; namely, by placing a hollow hemispherical reflector above the light, and a peculiar conoidal (convex) reflector below it, the arrangement being such that all the light reflected above the level of the source is thrown back, and with that falling below the horizon, also, is then thrown off from the lower reflector in horizontal beams. With this arrangement, as with the dioptric, the entire horizon can, if desirable, be illuminated. Cuts of the arrangement for the mercury light and the form of the proposed new reflector accompany the article from which the facts detailed in this section are in good part taken. Way's Electric Light, with Mercury.-In the autumn of 1861, Prof. Way visited this country and made several exhibitions of his electric light, one of these being (by aid of a Fresnel lens of the 4th order, loaned for the occasion) from Fort Washington, near Washington, D. C., the signals being witnessed by the President and others from the "White House," a distance of 13 miles. This light is produced by means of a fine thread of mercury kept flowing in the position answering to the focal point of a suitable reflector or Fresnel lens, this mercury being at the same time rendered intensely luminous by the continual passage through it as a conductor of a strong current of electricity. The mercury flows from an upper reservoir, through a tube with a very fine opening, into a lower The positive and negative wires com one. municate with the mercury in the respective reservoirs; and the circuit is complete only so long as, by the opening of a stopcock, the mercury is allowed to flow. The current is usually generated by a battery of about 45 Bunsen's elements. In the production of the recent and somewhat famed magnesium light, a continual consumption of the fine thread of the metal goes on; in other words, it is rapidly burned, as a taper; and the cost of the metal is one of the objections to the method. In Way's light, however, the mercury is not consumed, but can be used repeatedly, and without apparent deterioration or loss. True, the electricity dashes the metal to some extent against the glass tube which includes the filament of mercury, thus in time coating this tube with patches of the metal that interfere with the transmission of the light; this effect, however, is but slowly produced, and the tubes are readily changed and cleansed. Two other, and, it would appear, yet more objectionable features of the mercury light, require mention. In the first place, this metal, like most or all others (see SPECTRUM OBSERVATIONS), does not when rendered incandescent shine, as do the ignited carbon points, with light of all the colors found in the sunbeam. In fact, it gives out rays of a limited and very small number only of the sorts going to make up the entire spectrum; since, on prismatic analysis, it is said to yield six narrow and definite bands of color only: viz., a brick red, a yellowish orange, two emerald greens near together, a rich blue, and a violet; it is in addition, however, very rich in actinic rays, or those effective in producing the photographic impression. Employed to illuminate dwellings, halls, or natural scenery by night, this light would accordingly show as black or gray all objects having colors other than those of the rays composing it. In the second place, though the mercury used in producing the light is not oxidized, yet the intense heat arising in the filament which is rendered luminous also serves to volatilize the mercury at certain points, so that minute breaks in the thread of the metal occur, and the light is hence a flickering, and not a steady one-a difficulty for which perhaps no remedy can be found. Improvement in Holmes' Magneto-Electric Light.-Prof. F. H. Holmes has a letter in the "Athenæum" of Jan. 3, 1863, in which he states that such improvements have lately been made in the lamp employed in his system, that the movement of the carbon points is no longer effected through a delicate and complicated clockwork, but by means of a single wheel and pinion. The lamps in use at Dungeness and at Northfleet, the former 7 months, the latter still longer, have not in all that time been opened, even to be oiled. In the new arrangement, if the light be arbitrarily extinguished, it immediately relights itself, and it is no longer liable to spontaneous extinction. The only remaining source of interruption is the presence of silica or metallic residua as impurities in the carbons. Thus, when these have wasted to a point at which iron or antimony occurs, there is a slight change of color and momentary flicker, but which are of no practical consequence. In the new arrangement, the attendant of the steam engine can learn in a few hours all that requires to be looked after. The electric light does not, like the oil lights, necessitate an interruption for trimming, a process that with the latter must be performed at least as often as once during each night. The actual expense of the former still remains somewhat the greater; but if its increased intensity and penetrative power be taken into the account, it is really the cheaper; and the qualities just named can be greatly augmented at a slightly increased ratio of expense. Serrin's Electric Light Regulator.-Those specially interested in the subject of electric lights may be referred to an account of the principle of operation of the regulator for such lights devised by M. Serrin, originally appearing in the Comptes Rendus, and quoted in the "Journal of the Franklin Institute," Dec. 1862. Briefly, the method is that of holding the carbon points very near to each other by means of springs, but preventing the bringing of the points into positive contact so as possibly to interrupt the light, by so disposing in the apparatus or regulator containing the points an electro-magnet, the armature of which falls as often as the circuit is in such manner completed, that the weight of this armature just overbalances the tension of the lower springs sufficiently to depress the lower carbon to a very slight extent. Baker's Apparatus for Electric Lights.-Mr. A. L. Fleury exhibited at a meeting of the Franklin Institute, April 17, 1862, a magnetoelectric machine, and also a mechanism for electric lights, the inventions of Mr. H. N. Baker, and constructed by Messrs. Collier and Co., of Binghampton, N. Y. The mechanism for controlling the relative positions of the carbon points is extremely simple. The carbons are in form of long cones or pencils, and placed vertically, one over the other. A hole in an upper metallic strap or bridge, is of such size that the carbon pencil sinks only to a certain depth in it; while a hole in a lower strap is large enough to allow the lower pencil to rise freely through it. While the current is passing, as is usual, particles are carried off from the positive carbon electrode and deposited on the negative one. Thus, the former wastes, and the latter may be injured by becoming blunt or coated with irregular deposit. To prevent the unlike effect on the two pencils, Mr. Baker resorts to the French system of continually reversing the current; and the waste of both pencils thus becomes similar. Now, the lower pencil being placed as a float (though on what liquid the account does not state), it results that, as the gradual waste goes on, the upper pencil is simply fed downward continual ly by its gravity, while the lower one is just a regularly fed upward by its buoyancy. This is the arrangement when a current of larz "quantity" and low intensity is employed, the electrodes being in such case satisfactorily ig ed although they continue in actual contact, When, however, a current of high intensity is employed, the pencils are allowed only to sp proach very close, but without touching; and to accomplish this, the hole in the lower strap is also made so small as to admit a certain length only of the pencil. It would appear that the apparatus operates successfully on the scale on which it has been tried, or as an eleetric lamp; and it is said to be extremely cheap, (“Jour. Fr. Inst.," May, 1862.) The Present Desideratum in Electric Light -The magneto-electric light, which is prob ably the most economical in use, has still the disadvantage of the great waste of power ne cessarily attending the successive transforms tions of a given amount of force. In producing this light, the heat developed by the combus tion of coal is converted, first, into mechanical power; the mechanical power must then be transformed into electricity, and this finally into a heat which shall result in light. Now, M. Joule has shown that in the first of these transformations, even when effected under fa vorable circumstances, no more than part of the heat is actually realized in mechanical power, of the force developed from the coal being lost. This loss of power, and of useful effect, is strikingly illustrated in the case of the English and the French ice-making machines in the Exhibition of 1862. These machines alike derive their capacity of producing ice from the combustion of coal. But while, in the English machine, the heat of the coal is first converted into the mechanical power of a steam engine, and the product is but two tons of ice per ton of coal consumed, in the French machine this preliminary transformation of the heat through the driving of an engine is dispensed with, and the product is declared to be from 10 to 13 tons of ice for each ton of coal burned in the furnace of the apparatus. These considerations indicate the direction in which the improvement (in econo my) of the electric light should be sought. The object aimed at should be that of transforming, as directly as possible, the heat generated by combustion of coal into electric current-force. It is remarked by Dr. Frankland, from whose account of "Illumination" in the "Record of the Great Exhibition, 1862, these thoughts are drawn, that the researches of Dr. Matthiessen on the thermo-electric properties of tellurium promise important results in the direction here indicated. Electric Light Signals.-The electric light, in whatever mode produced, admits of being instantaneously extinguished and as quickly relighted. Hence, it can be made at will to shine or disappear; and a system of signals with h a light, by timing successive flashes acding to a prearranged order of long or short hes and repetitions, thus becomes practica. Such a system of flashing lights with the snel lenses is already to some extent in use; 1 for field operations, as well as in some es for lighthouses, it may be rendered of at value. For a system of this sort, the ne of Photo-Telegraphy has been proposed. other mode of this telegraphing by light, is t of successive flashes of different colors. . Wm. C. Bridges, of Philadelphia, has inited an apparatus for this form of light sigs, consisting of a tube and lens, with adjuste mirrors as may be required, and differentcolored and also opaque glass slides, to be ved at will in front of the lens. The electric other light shining continually into the tube, slides determine by color and intervals of > flashes the character of the signals made. any mode, the light signals could be, by a stomary system, or by systems, secret to all t initiated parties. Application of the Electric Light to Mining urposes.-MM. Dumas and Benoit have desed a compact and highly portable appatus, its entire bulk not exceeding that of a all carpet bag, including a battery, a Ruhmorff coil, and a Geissler's tube, within which e light is generated; the arrangement proacing sufficient illumination to enable a iner to work by it, as by a Davy's safetymp. This light serves equally well in an atosphere in which all others fail; while, the ght being cold, and its production wholly ithin a confined tube into which gases have o access, it is perfectly safe against explosion nder all circumstances. The arrangement will ive light for 12 consecutive hours with no atention save that the workman must occasionly agitate the carbons by means of a rod; and t is instantaneously lighted or extinguished at will, while no injurious emanation arises from it. From results obtained with the use of Becquerel's fluorescence-tubes, it is supposed that the luminous effects are susceptible of further great improvement, both in respect to duration and intensity. This light, or some other similar in principle, is certain to possess value for other purposes besides mining. Thus, in coal oil factories the best safety lamps are said to fail, since the subtile benzole vapors may take fire through the finest wire gauze. Here, the electric light, within a closed tube, would be entirely safe; and it would also prove peculiarly appropriate where danger from the dashing of water may exist, as in the interior of gunboats and steam rams, and even in diving bells. Engraving by Electricity.-The cylinders of copper brass employed in the printing of woven fabrics and paper-hangings are by a recent invention engraved by means of electricity the voltaic current being so applied as to communicate the necessary movements to certain portions of the apparatus. The cylinders to be engraved are first coated on their outer surface with a thin film of varnish, of such nature as to be capable of resisting the continuous action of the strongest acids. The requisite number of copies of the original design are then traced or scratched simultaneously by a series of diamond points, which are arranged on the machine parallel with the axes of several cylinders operated on at the same time. Each diamond point is in correspondence with a small temporary magnet; and the original design having been previously etched on a metal cylinder fitted in with a non-conducting substance, and this cylinder being made to revolve in contact with a tracing point, it results that the current passes, or is interrupted, through the entire series of coils of the electro-magnets, securing the contact of each diamond point with its corresponding cylinder, or the reverse, according as the point rubbing on the first cylinder touches a conducting or a non-conducting portion of its surface: in this way, while the cylinders all revolve at the same rate, the diamond points are made to cut upon all but the first, or are raised from them, and at the same moments. The metallic surface is hence exposed in like parts on all the cylinders operated on; and a bath of nitric or other acid being afterward used to etch or deepen the engraved portion, the operation is completed. By interposing suitable connections, the engravings can be enlarged or diminished to any ne cessary extent from the same original. Electric Despatch.-The experiment in which a bobbin or coil of wire conducting a current of electricity draws within itself an iron rod of the length of such bobbin, or even sustains the rod, when the arrangement is vertical and the power of the current sufficient, against the force of gravity, is now familiarly known. Availing himself of the converse of this principle, Mr. Henry Cook, of Manchester, England, has constructed and patented an electric propeller for transporting despatches, letters, and other small articles. A line of miniature railway is laid within a tube or pipe extending between the points of communication, and formed of a series of hollow electric coils or electro-magnets. The carriage on which the despatches or other small parcels are transmitted, has mounted upon it a small battery; and the ends of the coils are so adjusted that, by means of the wheels and rails, the battery connection is made successively with each of the coils, just as the wagon is about to enter it: The wagon itself being of sheet iron, it will be attracted toward the middle part of each coil, as the latter is thus made for the time to transmit the current generated by the battery upon it; and the momentum thus acquired by the wagon in entering each of the coils is expected to carry it far enough to make the connection with the next coil, when the impulse and effect are renewed. The suggestion of this device appears to have been made by M. Bonelli. Electric Sounding Apparatus.-This appa ratus, the invention of M. Schneider, was successfully employed in soundings on Lake Ladoga in June, 1862. The sounding line was of gutta percha, 2 lines in thickness, 1,800 feet in length, and covered. It contained two wires, one inside the gutta percha, the other within the outer covering. Bruck's sounding apparatus was used, the weight of the leaden plummet being 12 lbs., but with the modification that no part was detached by contact with the bottom. The wires of the line communicated with a battery on board, of 6 elements; and at the moment of the plummet's touching bottom, the current through the wires being established by contact with the earth, an alarm clock attached to the apparatus was sounded. This result was tested by using the electric sounding apparatus at the same time with Bruck's, which operates upon a more usual system; and it was found that even if the bottom were soft and muddy the alarm was still given at the moment of contact. The steamer on board which the trial was made being of iron, M. Schneider experimented to some extent in the way of making the vessel serve as the upper metallic plate, the sounding apparatus serving as the lower, and so employing in the soundings only one of the wires: the result of these experiments also was entirely satisfactory. The apparatus is stated to be cheap and easily managed, and likely to be serviceable for deep-sea soundings. ELLET, CHARLES, jr., an American engineer, born at Penn's Manor, Buck's Co., Pa., Jan. 1st, 1810, died at Cairo, Ill., June 21, 1862. He was a thorough master of his profession, and his name is identified with several of the most important works in the country. He designed and built the wire suspension bridge across the Schuylkill at Fairmount, Philadelphia, the first in the United States, and subsequently the suspension bridge across the Niagara river below the falls, and one at Wheeling, Va. He constructed the temporary track of the Virginia central railroad across the Blue Ridge, and contributed largely to the improvement of the navigation of the Kanawha river. He aided also in laying out the Baltimore and Ohio railroad, and there are indeed hardly any of the Western or Middle States which do not furnish some lasting evidence of his professional skill. In 1846-7, he was president of the Schuylkill Navigation Company. At the outbreak of the war, in 1861, he was residing at Washington, where he became deeply interested in the conduct of military matters, and devoted much attention to the use of rams in naval warfare. He projected a plan for cutting off the Confederate army at Manassas, which being rejected by Gen. McClellan, he wrote two pamphlets severely censuring his mode of conducting the campaign. The navy department having rejected his plan for the construction of rams for service on the Mississippi, he applied to the secretary of war, and was successful. He was commissioned as colonel of engineers, and con verted several powerful steamers into raz which did effective service in the naval bete off Memphis, in which engagement he receive the wound whereby he lost his life. He Ta the author of an "Essay on the Laws of Trade in reference to the Works of Internal Improve ment in the United States;" a paper **On the Physical Geography of the Mississippi Valley, with suggestions as to the Improvement of the Navigation of the Ohio and other Rivers," pr lished in "Transactions of the Smithsonian Lstitution;" a pamphlet on "Coast and Harbr Defences, or the Substitution of Steam Batte ing Rams for Ships of War," and several other important and valuable scientific papers. EXHIBITION, BRITISH INDUSTRIAL. The first International Exhibition was opened by her Majesty, Thursday, May 1, 1851. The exhibition remained open 141 days; its for exhibitors were 6,556, and the exhibitors cf the United Kingdom and dependencies, 7.38 (exclusive of India), forming a grand total of 13,938. The whole daily admissions by par. ment amounted to £5,265,429; by season tich ets, £773,766; together, £6,039,195. Average visitors on each day, 42,831; greatest number present, on October 7, 109,915; greatest ber at one time in the building, October 7.8,224. Commissioners' receipts from all sources, to Feb. 29, 1852, including subscriptions, £5. 100 68. 11d. Expenditure, £292,794 11. &l. Balance, £213,305 158. 8d. To enable the royal commissioners to apply this surplus and keep faith with the subscribers to the original furd, they were empowered by a supplemental char ter to purchase and hold lands in any part of her Majesty's dominions and dispose of them s they thought fit. They first proposed to provide a house for the Trade Museum, a collec tion of articles valued at £9,000, presented to them by exhibitors in 1851. For this purpose, they purchased the "Gore House estate," at one time owned by Mr. Wilberforce, and subsequently by the Countess of Blessington. The whole estate comprised about 21 acres, added to which were Gray's nursery grounds, Park house, and Grove house, and various market gardens, the grounds of Cromwell House, and other lands belonging to the Earl of Harrington and the Baron de Villars. Additional funds for these purchases were provided by the Govern ment, who entered into a sort of partnership with the commissioners, and purchased, in all, 86 acres, for £280,000, at an average of £3,250 an acre. The object of these purchases of land was to secure a large space to which some of the national exhibitions might be removed, and on which a great art-educational institution might be erected. Early in 1858, the commis sioners dissolved partnership with the state; the sums advanced by Government were repaid by the commissioners, subject to a deduction for the ground and buildings of the South Kensington Museum, now become a government institution, as a branch of the department of science and art. The commissioners now be |