go on round the whole circle, and round again with continual division of error thereby. It thus affords fractions of the finest possible direct readings of the instrument. Special instruments, with horizontal or vertical limbs, mounted expressly for repeating, are called "repeating circles." Borda's Vertical Repeating Circle, used by the French for measuring the meridian from Dunquerque to Barcelona, upon which the metre was based, is a celebrated instrument of this class. (To be continued.) ROLLER BEARINGS. NE would think it rather late in the day for drive and retain the wedges, so as to make and roller bearings to axles, shafts, &c., but Messrs. J. G. Avery and W. Tucker, of Massachusetts, have recently obtained letters patent in this country for improvements in roller bearing or bearing surfaces for axles, shafts, slides, and other rotating, oscillating, or reciprocating parts. The invention relates to the application of "friction rollers" to horizontal or nearly horizontal axles, shafts, and other mechanical objects which rotate or oscillate, or support rotary or oscillatory wheels or the like, and to crossheads and other slides of every description, as a substitute for lubrication. It comprises the employment or use of rollers of hardened steel or equivalent material, in combination with "coacting" surfaces, having faces of like material or hardness. Any indentation or "detrusion" of either surface is thus prevented, and the continuous efficiency of the rollers is insured. The invention also com-threaded externally. Split wedging rings fit | proper disallignment of the rollers longitudinally prises the combination of a sleeve of hardened into the enlargements, and nuts screwed on ends is secured; the rivet holes (which alone distinguish steel, having conical enlargements in its ends, a the second and succeeding rings from the first pair of split wedging rings adapted to be forced one) being drilled at certain uniform distances into the enlargements, and a pair of clamping from the axes of the several roller cells. A sufnuts screwing into the ends of the sleeve to conficient number of the rings, with their complefine the wedging rings. By this means machine ment of rollers, must be attached successively, shafting can be provided at any point with a conand a flat cap ring, V, simply provided with rivet centric hard facing, to co-operate with hard holes, completes the sleeve. The number and friction rollers in a very simple manner. It also In applying this invention to slides and their proportions of the rollers, and other mechanical comprises the employment of short journalless guides the facings may be formed on or attached details will vary in the manufacture of roller rollers in solid contact with opposite coacting to the iron in any convenient manner. The carriers of different forms and sizes. For long surfaces in combination with a carrier having rollers may be in all cases substantially bearings of a given diameter any length or a socket or cell for each roller, and sup- the same, differing only in proportions, and lengths, or fractional lengths of the described ported out of contact with the coacting surfaces they may be cut from bar steel and suit-carrier sleeve may be annexed, and in this case by rollers, thus preserving the arrangement of the ably shaped, tempered, and finished, or they there may be two or more rollers in line with rollers with the least possible addition to their may be made of cast iron, hardened in chills. each other longitudinally. works. The invention also comprises the employ- Each set of rollers will consist of one or more ment of several parallel series of short journal- series, and each series of several rollers, whose less friction rollers, in combination with a carrier axes are at right angles to the line of motion, having a socket or cell for each roller, the latter and parallel to each other. To preserve this arbeing so arranged that the axles of no two rollers rangement of the rollers, and to provide for adare in line with each other longitudinally-the ditional features of distribution, each set of rollers support being thus distributed in a uniform is mounted in a carrier, C, having a socket or cell manner, insuring the practically constant for each roller, the cells being bored so that the presence of the rollers in succession in any given rollers will have just enough room to rotate line of pressure or concussion. freely. Eh room to rotate This carrier is sufficiently thin to cause the rollers to project beyond their cells into contact with the facings of the coacting surfaces, while the carrier is supported out of contact with the surfaces by the rollers. The latter are journalless and in solid contact with both of the coacting surfaces while under pressure. The only function of the carrier is consequently to preserve the order or position of the rollers before the parts are put together, and while they are in use, and in the case of slides, when the latter pass out of contact therewith. To reduce the slight friction between the rollers and the carrier, the latter may, in some cases, be made of antifriction material. Fig. 1 represents a longitudinal section; and Fig. 2, a transverse section of an axle and its hub-box. Fig. 3 is a side elevation of the interposed carrier sleeve and rollers; Fig. 4, a face view of one of the sections of sleeve; and Fig. 5, an edge view of two sections, showing the mode of uniting them. The patentees show several modifications of the roller bearings, but in principle they are practically the same, and are simply adapted to the conditions. STEPHENSON'S EMBOSSED PLATES In carrying the invention into practice the patentees form or attach facings, Z, Y, of hardened steel or other suitable metal on the opposite surfaces of the two objects, A, B, between which friction is to be prevented, facings being equidistant at all points with sufficient space between them to accommodate smooth cylindrical rollers, X, of proper diameter and In Figs. 1, 2, 3, the rollers are shown as close as The plates of a boiler exposed to the action of extent, the rollers being of hardened steel or its practicable in several parallel circumferential fire, particularly those which form the sides of equivalent, to correspond in hardness with the series, with no two rollers exactly in line with each the firebox, are usually supported by staybolts facings. The rollers are thus adapted to preserve other longitudinally. There are consequently as passed or screwed through them and secured to their shape indefinitely, while the hardened many axes as there are rollers, and one roller the outer shell or to other plates separated from facings co-operate therewith to prevent ob- must be brought directly into the line of pressure the former by a water or steam space. As the struction by indentation or "detrusion." To almost immediately when the axis of another plate and the head of the staybolt become make an axle or spindle, A (Figs. 1, 2), hard passes out of this line. Thus every sudden jar or corroded, scaled, or burnt the hold of the stay on externally to a minimum depth, to resist the de- blow will be resisted by the mass of some roller the plate and the plate itself are so much structive wearing action of the rollers upon it, directly interposed in the line of concussion, the weakened that the latter frequently gives way, and at the same time soft internally, so as to other rollers assisting, and no heavy pressure and serious accidents sometimes occur from this possess the requisite strength, the patentees pro- can force any two rollers apart, or cause them to cause. The object of the invention is to strengthen pose to wind a thin coil of steel upon an iron bar bind in their sockets. The roller carriers are such plates in the parts through which the stay. or upon a bar of steel of a quality which will each constructed in the form of a sleeve by the bolts pass, to give the staybolts a better hold not harden in the usual manner, and weld and following process:-A narrow ring W (Figs. therein, and to protect the stays as well as the draw the same in dies. The hub-box, B (Figs, 4 and 5) contains equidistant sockets or cells for strengthened portions of the plates from the de1, 2) may be made with steel welded inside, or one circumferential series of the rollers X, the structive action of the heat. For this purpose of steel or iron that will surface harden, or cells being drilled in one edge of ring with their those parts of the plates through which staybolts of chilled cast iron, and finished by grinding it axes parallel to its axis, and equidistant from its are to pass are subjected to a squeezing action out in any usual way. In applying this invention inner and outer surfaces, beyond which the in-produced either by pressure or blows between to rotary shafts or shafting, the hard facing, in closed rollers project, as before explained. The blunt punches and hollow dies so that the metal the form of a sleeve of hardened steel or its ollers are inserted longitudinally and secured by of the plate is at each stay place hollowed in on equivalent, is bored out at its ends to form iveting another ring to the first ring, W, as the one side and made to project as a boss on the conical enlargements, and the ends are screw-illustrated in Fig. 5. At the same time the other side. In some cases the stay bosses produced of current thus generated and the oscillations of a steam, gas, water, or other fluid under pressure acts defective of the machines we have named. Mr. within the cylinder, being admitted first to one side Edison adopted the arrangement with the idea of of the piston and then the other by a suitable valve; reducing the power required to develop the electhe valve and directing rod 2 are shown for this tricity he needs. If we have two electro-magnetic purpose. The bar of fork a2 may be a permanent machines, one theoretically much less efficient than magnet or an electro-magnet, or else it is provided the other, it may nevertheless be practically the with permanent or electro-magnets. I have shown better of the two, provided it produces electricity there may be two or more on each and opposed to rival; and thus, although Mr. Edison might use his an electro-magnet cl upon each prong of the fork with much less expenditure of power than its these are the cores of the electro-magnets. Hence magnets and wires to great disadvantage, yet if the as the fork is vibrated a current is set up in the power required to actuate them was very small, he helix of each electro-magnet d in one direction as would be justified in following the course he has the cores approach each other, and in the opposite actually adopted. But in truth, Mr. Edison is direction as they recede. This alternate current is entirely mistaken in his notions on this point. The available for electric lights, but if it is desired to fact that a tuning fork can be kept in vibration convert the current into one of continuity in the with the expenditure of little power has no more to same direction a commutator is employed, operated do with the matter than the circumstance that the by the vibrations of the fork to change the circuit well-lubricated journals of a Gramme machine connections each vibration, and thereby make the offer small resistance to the engine driving it. A LL anxiety concerning the Edison light, says the pulsations continuous on the line of one polarity. strict analogy exists between the vibrations of a tainly not going to take the place of gas, and its through the helices of the the electro-magnets cl to Now, if we substitute a pendulum for the vibrating invention would not have been regarded with the intensify the same to the maximum power, and the bar patented by Mr. Edison, and fix an electroanxiety and interest which have been displayed had remainder of the current is employed for any desired magnet to its lower end, which, when the pendulum it not been for the statements of newspaper reporters electrical operation wherever available. I, how-swings, will cut the field of a magnet placed just on the other side of the Atlantic. The invention is ever, use the same, especially with my electric divided into two parts-the first refers to the means lights, but I remark that electricity for such lights of producing electricity, the second to the lamp. may be developed by any suitable apparatus. I The electro-magnetic machine is thus described show commutator springs or levers c3, c4, operin the specification. "It has long been known that ated by rods that slide through the levers c3 c4, and if two electro-magnets, or an electro-magnet and a by friction move them. When the prongs a2 a2 are permanent magnet, be drawn apart or caused to moving from each other the contact of levers c3 c4 pass by each other, electric currents will be set up will be with the screws 40 41, and the current will in the helix of the electro-magnet. It has also been be from line 1 through el to c, thence to c3 to 41, known that vibrating bodies, such as a tuning-fork 43, and to circuit of electro-magnets d d, and from or a reed, can be kept in vibration by the exercised d by 42 to 40 4, and line as indicated by the of but little power. I avail of these two known forces and combine them in such a manner as to obtain a powerful electric current by the expenditure of a small mechanical force. In Fig. 1 of the drawing a tuning fork a2 is represented as firmly Mr. Edison has probably succeeded in producing attached to a stand 62. This fork is preferably of the very worst magneto-electric machine ever made two prongs, but only one might be employed upon that is to say, if he has really ever constructed one the principle of a musical reed. The vibrating bar according to his specification, which we much doubt. or fork may be 2 metres long, more or less, and With a very little expenditure of space on our part, heavy in proportion. It has its regular rate of we hope to make this clear to our readers. Mr. vibration like a tuning fork, and the mechanism Edison cannot imagine for a moment that the systhat keeps it in vibration is to move in harmony. tem of producing currents by magnets which apA crank and revolving shaft, or other suitable proach to and recede from each other, as described, mechanism, may be employed, but I prefer a small can be in any respect equal to that on which the air, gas, or water engine, applied to each end of the fork. The cylinder al contains a piston and a rod 61, that is connected to the end of the bar, and tion which will permit the armatures and magnets to approach each other as closely as possible without touching. The effect of the hammering of the prongs on the stops may be imagined. Finally, the armatures ought to approach to and recede from the magnets not less often than 1,000 times in a minute. Does Mr. Edison really imagine that he can make a tuning-fork "2 metres long" vibrate over sixteen times in a second? What is the engine to be like that will make sixteen strokes per second? Any attempt to work to Mr. Edison's specification would give a slow-moving, heavy machine, very much inferior to anything now in the market. We need say nothing more concerning this part of his in vention. In this country, and, indeed in the United States, little has been heard about the Edison electromagnetic engine, and it is possible that he himself attaches very little value to it. It was not any terror of its advent that induced people to sell their gas shares. The Edison lamp was the real cause of panic among the gas makers, and of hope among the gas users. In our last impression we published a small engraving which illustrates the principle of the Edison lamp very clearly. Fig. 2 shows the actual lamp, thus described by the inventor: lighting our houses an electric lamp has probably warm objects. It took the form of small, flattened and irregular pastilles. The phenomenon was especially remarkable on woollen stuffs. The drops had evidently been brought to a state of surfusion in their passage through cold air, so that they immediately solidified on meeting solid bodies. When the rain was plentiful, on the other hand, part of it was at once changed to ice, but part flowed down on solid bodies, forming a new layer of ice, and producing stalactites. The ice-covered branches of trees broke more and more under the weight, and on the evening of the second day the phenomenon assumed frightful proportions. Crack succeeded crack with growing rapidity. In the morning the ground was strewed with branches, whole trees lay prostrated and uprooted, and others were split in fwo from top to base. The majority were entirely cleared of their branches, and in some parts the forest looked like one of masts. Such effects will not excite surprise if figures like the following be considered:-A twig from a lime was weighed, and the balance showed 60 grammes per decimetre of length. The same twig, deprived of ice, weighed only 0-5 gramme. A leaf of laurel carried a carapace of ice weighing 70 grammes. All objects exposed were alike covered with ice. M. Piebourg, writing from Fontainebleau, mentions that shrubs with persistent leaves, such as rhododendrons and alaterns, became one block of ice, through which leaves and branches could be distinguished pretty well. Fir trees and the like had the appearance of a huge pyramid of ice, each group of branches being weighed down on the one below, and the shrubs broke up mostly during the thaw, which lowest on the ground. These trees and evergreen commenced on the 25th. The fracturing of the leafless trees, on the other hand, occurred earlier, as the ice accumulating on their branches. ON CERTAIN MEANS OF MEASUR- THE With all its defects for domestic purposes, still Mr. Edison's lamp might perhaps be used to much advantage for street lighting, and in factories or theatres; in fact, in any situation where it could be looked after by a skilled attendant. If the current can be successfully divided among dozens of such lamps, then may gas-makers quake; but nothing of the kind can be done. We know at last that Mr. Edison has done no more to divide the electric light to advantage than has Mr. Werdermann. We have not thought it necessary to reproduce the rough little diagrams by which Mr. Edison illustrates that portion of his specification which deals with this branch of the subject. Practically, the arrangement is very similar to that of Werdermann. We reproduce the following portion of Mr. Edison's specification, omitting the figures and the references to them, as we fancy the passage will be intelligible without them:-"In lighting by electricity it is often important to use a secondary battery in connection with the main current. Electric light coils may be put in a secondary circuit containing cells, with plates in a conducting liquid, and a lever is vibrated by an electro-magnet or by clockwork. When the lever is in contact the "Platinum and other materials that can only current from line 1 passes through the electrobe fused at a very high temperature, have been employed in electric lights: but there magnet and cells, but when the contact ceases the line is closed, but a local circuit is made through is risk of such light-giving substance melt- the coils and secondary battery; the discharge ing under the electric energy. This por- of the secondary battery gives the light, and tion of my invention relates to the regulation of the the movement is so rapid that the light appears electric current, so as to prevent the same becoming continuous. so intense as to injure the incandescent material. introduced with one or more lights, the expansion A single secondary battery may be The current regulation is primarily effected by the of the light-giving material short circuiting the heat itself, and is automatic. In Fig. 2 I have current through the secondary battery. Instead of shown the light-producing body as a spiral a, a rheostat in the shunt circuit I sometimes employ connected to the posts be, and within the glass cylinder g. a button of carbon. In this case the spring lever This cylinder has a cap, and stands bearing upon the carbon button, lessens the resistupon a base m, and for convenience a column and ance by the increase of pressure as the platina strip stand o, of any suitable character, may be em- expands, and ployed. Most of the other figures are in the form pressure on the carbon button the resistance of that as it contracts and lessens the of diagrams to more clearly represent the electrical carbon button increases, and a greater portion of connections. I remark that it is preferable to have the current is sent through the platina strip. This the light within a case or globe, and that various regulation is very accurat." It will be remembered materials may be employed, such as alum water, that in our impression for November 8th, 1878, between concentric cylinders to lessen radiation, p. 339, we suggested that it was possible Mr. Edison retain the heat, and lessen the electric energy required; had adopted this very device for preventing the or coloured or opalescent glass, or solutions that combustion of the platinum foil. reduce the refrangibility of the light, such as sulMr. Edison's claims are as follows:-" (1) The phate of quinine, may be employed to moderate combination with an electric light of a thermal cirthe light, and the light may either be in the atmo- cuit regulator, to lessen the electric action in the sphere or in a vacuum. The materials that I have light when the maximum intensity has been attained found especially adapted to use as light-giving substantially as set forth; (2) The combination with substances are set forth hereafter. The electric the electric light of a circuit closing lever, operated circuit, Fig. 2, passes by line 1 to the post r, and by heat from the electric current or from the light, by a wire to the lever f, then c by the wire or rod k, and a shunt or short circuit to divert the current cap 1, wire e, to the post e, through the double or a portion thereof from the light, substantially spiral a to the post b, and by a metallic connection or wire to the post 1 and line 4, and so on through electric light and a resistance of as set forth; (3) The combination with the 2 circuit the electric circuit, and the light be developed in a closer operated by heat, and serving to place The rod / will expand in proportion to the heat of more or less resistance in the circuit of the electric the coil, or in proportion to the heat developed by light, substantially as set forth; (4) The combination the passage of the current through the fine wire with an electric light of a diaphragm operated by k, and, if the heat becomes dangerously high, the expansion of a gas or fluid in proportion to the injury to the apparatus is prevented by the expan- temperature of the light to regulate the electric cursion of rod k moving the lever f, to close the circuit rent substantially as set forth; (5) The combination at i and short circuit or shunt a portion of the with a vibrating body similar to a tuning-fork of current from the coil a, and reducing its tempera- mechanism for maintaining the vibration, and magture; this operation is automatic, and forms the nets, cores, and helices, whereby a secondary current principal feature of my invention, because it effect- is set up, so as to convert mechanical motion into elecThe most essential part of the instrument is a ually preserves the apparatus from injury. The tric force, or the reverse, substantially as set forth; strip of copper, iron, or other metal, rolled extremely current need not pass through the wire or rod k, as (6) The combination with electric lights, substantially thin, through which the current to be regulated has the expansion thereof by the radiated heat from such as described, of means for regulating the elec- to pass. One end of this thin strip of metal is the coil a will operate the lever f, as indicated in tric current to the same, in proportion to the heat attached to a screw, by which its tension can be Fig. 3, but the movement is not so prompt. It is evolved in the light, so as to prevent injury to the insulated pulley, and down again to the end of a regulated. It then passes upwards over an elevated to be understood that in all cases the action of the apparatus, substantially as set forth." In all this it will be seen that we have not one short lever, working on an axis, armed with a current through the light-giving substance, and word concerning any new or extraordinary contriv-counter weight and with a lever, whose angular the circuit-closing devices play up and down at the ances for dividing the electric light. Mr. Edison position will be materially affected by any small contact-point, maintaining uniformity of brilliancy has many other patents in progress, but that which elongation of the strip that may take place from of light.' we have just dealt is, no doubt, the patent; that any cause. The apparatus further consists of a which has attracted more attention, and the publi- number of prisms of metal, supported by means of cation of the contents of which has been looked for metallic springs, so regulated by movable weights as to insure the equidistant position of each prism with more avidity than perhaps any other ever applied for in England. How far it justifies the from its neighbour, unless pressed against the neighhopes and fears which have been fostered concerning bouring piece by the action of the lever, in conseit, we have placed our readers in a position to judge this action one prism after another would be brought quence of a shortening of the metallic strip. By for themselves. It may not be improper to say be into contact with its neighbour, until the last prism fore concluding, that Mr. Edison's complete specifi- in the series would be pressed against the contact cation has not yet been filed in this country, and cannot be seen at the Great Seal Patent-office, or spring, which is in metallic connection with the terminal. anywhere else save Paris. short circuit or shunt is momentarily to lessen the BY C. W. SIEMENS, D.C.L., F.R.S. HE dynamo-electric machine furnishes us with a means of producing electric currents of great magnitude, and it has become a matter of importance to measure and regulate the proportionate amount of current that shall be permitted to flow through any branch circuit, especially in such applications as the distribution of light and mechanical force. On the 19th of June last, at the Soirée of the President of the Royal Society, I exhibited a first conception of an arrangement for regulating such currents, which I have since worked out into a practical form. At the same time, I have been able to realise a method by which currents passing through a circuit, or branch circuit, are ineasured, and graphically recorded. It is well known that when an electric current passes through a conductor, heat is generated, which, according to Joule, is proportionate in amount to the resistance of the conductor, and to the square of the current which passes through it in a unit of time, or H = CR. I propose to take advantage of this well-established law of electro-dynamics, in order to limit and determine the amount of current passing through a circuit. Most of the details of this invention, taken separately, are not new. The use of an incandescent substance was first patented in this country, not by King in 1845, as is generally believed, but by De Moleyns in 1841. The materials named by Mr. Edison, such as platinum, iridium, osmium, &c., have all been used or proposed to be used long since. In this direction, therefore, there is nothing about Mr. Edison's invention to encourage hope or excite fear. There remains, however, the device for protecting the incandescent material from overThe current passing through the thin strip of heating, and this is very pretty and ingenious, and metal will, under these circumstances, pass through will probably work very well in competent hands; but it is a delicate bit of mechanism, which must the lever and the line of prisms to the terminal, without encountering any sensible resistance. A not only be adjusted to begin with, but kept in adjustment with minute accuracy, or the wire coils second and more circuitous route is, however, proalluded in our Scientific News last week to vided between the lever and the terminal, cousistwill be destroyed or the light will go out. The the phenomenon of rain which freezes di-ing of a series of comparatively thin coils of wire of range of motion supplied by the expansion rod is rectly it reaches a resting-place. We now give a German silver or other resisting metal, connecting extremely small, nor do we see how it is possible to few particulars regarding the recent exhibition of the alternate ends of each two adjoining springs, augment this range. In a word, there is nothing the phenomenon in France from letters to the Paris the first and last spring being also connected to the about the lamp analogous in simplicity to a gas Academy. According to M. Godefroy, writing lever and terminal respectively. When the lever light, nor is it obvious that it can ever be made to from a place in Loiret, rain fell continuously for stauds in its one extreme position the contact pieces comply with the ordinary requirements of domestic three successive days (the 22nd, 23rd, and 24th of life. Mr. Edison will no doubt attain much success January) and yet the thermometer remained at 2, are all separate, and the current has to pass through at Menlo Park, where everything will be under his 3, and even 4 degrees below zero. When the rain Abstract of a Paper presented to the Royal Society, own control; but for the ordinary purposes of was scanty, each drop at once solidified, even on Jan. 30. WE A COATING OF ICE. the entire series of coils, which present sufficient aggregate resistance to prevent the current from exceeding the desired limit. rents. The variable rheostat is in this case dis- When the minimum current is passing, the thin metallic strip is at its minimum working temperature, and all the metallic prisms are in contact, this being the position of least resistance. As soon as the current passing through the apparatus shall increase in amount, the thin metallic strip will immediately rise in temperature, which will cause it to elongate, and will allow the lever to recede from its extreme position, liberating one contact piece after another. Each such liberation will call into action the resistance coil connecting the spring ends, and an immediate corresponding diminution of the current through increased resistance; additional resistance will thus be thrown into the circuit, until an equilibrium is established between the heating effect produced by the current in the sensitive strip, and the diminution of heat by radiation from the strip to surrounding objects. In order to obtain uniform results, it is clearly necessary that the loss of heat by radiation should be made independent of accidental causes, such as currents of air or rapid variations of the external temperature, for which purpose the strip is put under a glass shade, and the instrument itself should be placed in a room where a tolerably uniform temperature of say 15° C. is maintained. Under these circumstances, the rate of dissipation by radiation and conduction (considering that we have to deal with low degrees of heat) increases in arithmetical ratio with the temperature of the strip; the expan-sents the expansion of the strip or movement of the sion of the strip, which affects the position of the pencil m, and considering that the electrical resistlever, is proportionate to the temperature which is ance of the conductor varies as its absolute temperaitself proportionate to the square of the current-a ture (which, upon the Centigrade scale, is 274° below circumstance highly favourable to the sensitive the zero Centigrade) according to a law first expressed by Helmholtz, and that we are only here dealing with a few degrees difference of temperature, no sensible error will be committed in putting the value of R for R', and we have the condition of equilibrium S Cr=m action of the instrument. (T- T) S, C2 = (T′ − T) S But TT repre R S, (T" — T). R R' (1) root Suppose that the current intended to be passed through the instrument is capable of maintaining the sensitive strip at a temperature of say 60° C., and that a sudden increase of current takes place in consequence either of an augmentation of the supply of electricity or of a change in the extraneous resistance to be overcome, the result will be an augmentation of temperature, which will continue until a new equilibrium between the heat supplied and that lost or, in words, the current varies as the square by radiation is effected. If the strip is made of of the difference of temperature or ordinates. For metal of high conductivity, such as copper or silver, any other condition of temperature T" we have and is rolled down to a thickness not exceeding C = S 0-06 milim., its capacity for heat is exceedingly small, and its surface being relatively very great, the new equilibrium between the supply of heat and its loss by radiation is effected almost instantaneously. But, with the increase of temperature, the position of the regulating lever is simultaneously affected, causing one or more contacts to be Liberated, and as many additional resistance coils to be thrown into circuit; the result being that the temperature of the strip varies only between very narrow limits, and that the current itself is rendered very uniform, notwithstanding considerable variation in its force, or in the resist tance of the lamp, or other extraneous resistance which it is intended to regulate. It might appear at first sight that, in dealing with powerful currents, the breaking of contacts would cause serious inconvenience in consequence of the discharge of extra current between the points of contact. But no such discharges of any importance actually take place, because the metallic continuity of the circuit is never broken, and each contact serves only to diminish to some extent the resistance of the regulating rheostat. The resistance coils, by which adjoining contact springs are connected, may be readily changed, so as to suit particular cases; they are made, by preference, of naked wire, in order to expose the entire surface to the cooling action of the atmosphere. In dealing with feeble currents I use another form of regulator in which discs of carbon are substituted for the wire rheostat. The Count du Moncel in 1856 first called attention to, and Mr. Edison more recently took advantage of, the interesting circumstance that the electrical resistance of carbons varies inversely with the pressure to which it is subjected, and by piling several discs of carbon one upon another in a vertical glass tube, a rheostat may be constructed which varies between wide limits, according as the mechanical pressure in the line of the axis is increased or diminished. A steel wire of-say, 03 milim. diameter is drawn tight between the end of the bell-crank lever and an adjusting screw, the pressure of the lever being resisted by a pile of carbon discs placed in a vertical glass tube. The current passing through the steel wire, through the bell-crank lever, and through the carbon discs, encounters the minimum resistance in the latter so long as the tension of the wire is at its maximum; whereas the least increase in temperature of the steel wire by the passage of the current causes a decrease of pressure upon the pile of carbon discs, and an increase in their electrical resistance; it will thus be readily seen that, by means of this simple apparatus, the strength of small currents may be regulated so as to vary only within certain narrow limits. The apparatus first described may be adapted also for the measurement of powerful electric cur ..C" = R (T" − T), S S and (C'2 - C3) : = (T"-T-T' + T) R = (T-T) R SCIENTIFIC SOCIETIES. THE ROYAL ASTRONOMICAL, SOCIETY. HE Annual General Meeting was held on T Friday, the 14th inst., at the Society's rooms, Burlington House, Lord Lindsay, M.P., president, in the chair. John Marshall, Esq., of Albionplace, Leeds, and R. Palmer Thomas, Esq., of 13, North-villas, Camden-square, were elected Fellows of the Society. The Astronomer Royal presented to the Society a photograph of a picture of Miss Caroline Herschel, which had been forwarded to him by Lady Herschel. Lord Lindsay, in moving a special vote of thanks, mentioned that only two ladies, namely, Miss Caroline Herschel and Mrs. Somerville had been elected Associates of the Society. A photograph of Mrs. Somerville hangs in the Council Room, and this picture will form a very appropriate companion to it. The Society then passed to the consideration of the special business with respect to the livings of Hartwell and Stone, of which notice had been given in a circular. Lord Lindsay then proceeded to deliver the President's address on presenting the gold medal of the society to Professor Asaph Hall "For his Discovery and Observations of the Satellites of Mars," and for his determination of their orbits. After describing at some length the astronomical labours of Professor Hall previous to the discovery for which the Council have awarded him their medal, Lord Lindsay gave an account of the various unsuccessful searches for satellites of Mars which had been made previously to the opposition of 1877. During the favourable Opposition of 1830, Mädler searched in vain for a satellite of Mars, and came to the conclusion that if such a satellite existed, and if it possessed the same reflecting power as its primary, that it could not exceed the diameter of twenty-three miles, since a larger one could not escape discovery under favourable circumstances. The instrument employed in this search was of 3 inches aperture, and was the same he afterwards employed in his lunar work, and though at the time the conclusions thus drawn were considered hardly justifiable, still, as time wore on, and larger instruments were employed, Mädler's estimate obtained better consideration. Professor d'Arrest made a search for a satellite in the year 1864; this was again unsuccessful. In a paper in the Astr. Nachr., vol. 64, p. 74, earth to be 0-52, and with an assumed Mars for d'Arrest, assuming the distance of Mars from the the planet, computed the apparent elongation of a satellite which would revolve around the planet in a given time. Thus he showed that an elongation the period of Mars round the sun, or, in other of 70 would give the satellite a period greater than words, greater than 687 days. From this the inference was drawn that it is useless to search for a satellite at a greater distance than 70'. the value of a diagram in Webers or other units Storms from America. It tends somewhat to shake our faith, writes Mr. R. A. Proctor in the Newcastle Weekly Chronicle, in predictions of storms coming across the Atlantic, to learn, on the authority of so eminent a meteorologist as Loomis, that though on the average about eighteen storms cross the Atlantic from the United States to Europe, nearly all pass considerably north of Scotland. He infers from the evidence he has obtained, that, of well-marked storms leaving the coast of the United States, only one in nine passes over any part of England; one in six may occasion a storm somewhere near the English coast; but so many as one-half may give rise to a fresh breeze somewhere in Great Britain. They travel much more slowly across the Atlantic than over the United States. About half the whole number of thirty storms discovered by Loomis began in the Rocky Mountains, five in or near Texas; and four were distinctly traced to the Pacific coast. A Stray Balloon. Mr. Edward Johnson, U.S. Consul at Tampico, Mexico, in a letter written to a friend in Washington, and dated the 20th ult., says: "A balloon, evidently from some civilised country, about sixty or seventy feet in size, with a car and all the comforts for a voyage, made of silk, &c., was found at Osulwama by the Indians in the woods. They tore the silk from it, and stole everything that could be carried off, and refused to give any information on the subject, for fear they would have to disgorge. On the next evening, August 17th, while waiting for and watching the outer satellite, Professor Hall discovered the inner one, and obtained measures of it when at a distance of about 31" from the centre of the planet. The last doubts as to the character of the faint objects thus found having been dispelled by the observations of the 17th and 18th August, the discovery was officially announced by Admiral Rogers. The appearances of the inner satellite were most perplexing. Professor Hall says, "For several days the inner moon was a puzzle; it would appear on different sides of the planet the same night, and at first I thought that there were two or three inner moons, since it seemed to me at that time very improbable that a satellite should revolve round its primary in less time than that in which the primary rotates. To set this point at rest Professor Hall watched the satellite throughout the nights of August 20 and 21, and was satisfied that there was but one inner moon which performed its revolution in less than one-third of the time of the rotation of Mars. A case, as he observes, unique in the solar system. Lord Lindsay then passed to a discussion of the thethod adopted by Professor Hall for determining the orbits from his observations. The eccentricity of Phobos is about 1/30th, with a probable error of about 1/600th; but the eccentricity of Deimos is so small that we may consider the circular elements of this satellite as practically sufficient for the observaWe now come to what may be considered the most important outcome of Professor Hall's discovery, namely, the determination of the mass of Mars. The result he obtained from Deimos gives tions. 1 3095313 + 3485 1 307845610104 Seeing that these two determinations fall so nearly 3093500+3295 On concluding his address, Lord Lindsay, turning to Mr. Ranyard, said, "May I request you, acting as the Foreign Secretary of the Society, to place this medal in the hands of the Minister of the United States, to be transmitted to Professor Asaph Hall as the highest mark of esteem in the gift of the Royal Astronomical Society. Assure him at the same time of the deep interest we in England have ever felt in watching the progress of our beloved science in the hands of our cousins in the far West." Portions of the Annual Report were then read, SCIENTIFIC NEWS. picking it up, and the announcement remained a mystery until Professor Peters traced a mistake to its source, and found that the wrong web of a microg the had been specified as that used in making the measurements. A SERIES of lectures on sound was commenced The Davy Centenary was held, as announced, and kept to Greenwich time. About 20 miles The clocks of Glasgow are now synchronised of wire are in use for the purpose, 100 clocks from Greenwich Observatory. o'clock every morning the correct time is sent being under correction every hour. At ten with the striking of the hour on the clock at Simultaneously Greenwich, a bell is rung by the electric enrrent close to a regulator, which is thus checked. In order to insure absolute accuracy, a second current is obtained from wire connected with Glasgow Observatory. The electricity is ob minated by the electric light; five lamps were On Thursday week the Albert Hall was illu- tained from about 300 Leclanché cells, arranged in batteries of sufficient strength to work the hung from the top of the building, and the synchronisers on the twelve different lines of machine was worked by the engine used for wire; and, by means of a distributor wrought playing the fountains and cascades in the adjoin-hourly by the regulator, a current of electricity ing gardens. In such a place the light was, as is stated, no doubt cheaper than gas. method was employed. Siemens's The Duke of Northumberland, as president, is transmitted to each clock under control. On board the Racillia, of Newcastle, is an invention by which one steering compass is entirely superseded, and the dangers arising from the Wilson has on the bridge one of Sir William corresponding are entirely avoided. Captain and the meeting passed to the election of members has presented the Royal Institution with the bridge compass and that on the deck below not William of which he has fixed a wooden box. Inside of the compass, is placed a common mirror, in a this box, and immediately above the index card slanting position, so as to cast a reflection down to the compass-box on the deck beneath, where it is received by another ordinary mirror and thrown back again to the back of the compassbox, where the exact counterpart of the compass on the bridge above is distinctly visible to the man at the wheel. of council and officers for the coming year. A Cheap Bunsen Cell.-Mr. Wiesendanger has shown us one of his Bunsen cells as described by him on p. 468. Thirty of these cells give an excellent electric light with any of the well-known regulators, and being made of substantial materials, are not easily damaged. Looking at the substance of the zinc and the size of the carbon, they are remarkably cheap. illustration of his new system of illumination in The Zoetrope and the Phenakistiscope are wellknown toys in which a number of drawings representing the same objects in different positions are made, by rapid motion, to present the appearance of moving objects. In a new instrument, devised by M. Reynaud, and called a praxinoscope, there is no interruption in the On Vinous Fermentation.-In a posthumous vision nor sensible reduction of light, and the treatise by Claude Bernard "On the Vital Pheno-eye is enabled to view continuously an image mena common to Animals and Plants," the illus-resorts to a substitution of virtual images. The which is incessantly changing. M. Reynaud trious physiologist expresses some views on fermentation which are altogether opposed to the teaching praxinoscope consists of a circular case, open of M. Pasteur. Bernard endeavours to ascribe the above, on a vertical axis, and having a series of fermentation of grape-juice to the presence of a figures representing the phases of the action soluble ferment, acting chemically, and developed independently of the presence of specific organisms as a natural result of the maturation of the fruit. M. Pasteur set about repeating one of his old experiments on the subject. He had formerly demonstrated that the germs of the vinous ferment were not deposited on the surface of the grapes till a comparatively late stage in their development; that while the grapes were unripe they were alto- At a meeting of the scientific committee of the gether free from such particles. Accordingly, by Royal Horticultural Society last week Mr. wrapping up certain bunches of the fruit in cotton MacLachlan reported on a beetle which does wool, and enclosing others in hermetically-sealed much damage to the cocoa-nut palms in glass cases, in the latter part of July, he might antici- Zanzibar by eating and destroying the terminal pate that such protected bunches would yield a juice bud (or cabbage). It is the Oryctes monoceras. absolutely incapable of spontaneously entering on Dr. Kirk, who sent the specimen, stated that the fermentation. These anticipations were exactly fulfilled. When the grapes had reached maturity insect appeared in Zanzibar after a hurricane. (during the second week in October), they were The species has been found in Reunion by Dr. crushed with suitable precautions against accidental Coquerel. contamination. A pure saccharine must was thus obtained, which refused to ferment when main tained at a suitable temperature. Some of the protected bunches were allowed to be in contact with their unprotected neighbours for a short time before they were pressed; these yielded a fermentable juice, obviously owing to their having been infected with specific germs. round its interior circumference. Midway be- lately been patented by Major E. H. Cameron, Royal Artillery, whereby matches can be rendered waterproof. The process can be carried ont after manufacture with slightly increased cost. Matches have been soaked in water for twenty-four hours coated with Major Cameron's composition which A simple but useful invention has, it is stated, can be struck with a drop of water adhering. They can be ignited by friction on a wet as easily as on a dry surface. A large steel vessel for the Canadian cattle trade is about to be built by Messrs. Denny for Messrs. Allen. She is of 4,000 tons burden, and will be the largest steel vessel yet made. of 3,000 lire for the best monographic essay on long by 20 miles broad, and in parts 20ft. thick, of Oxford, will distribute the prizes awarded Professor Thorold Rogers, of the University by the Science and Art Department to the students of the Southwark, Stepney, Greenwich, and South-Western Railway, at the St. Olave's Grammar School, Tooley-street, Southwark, on the 28th inst. It is a common idea that light is always perProfessor Peters, of Clinton, N.Y., has set ceived, even though of very short duration, at rest a question which has agitated the astro-and the example is cited (not without reason) of nomical world more or less during the last 25 the extremely short electric spark. With weaker years. It was announced from Washington in lights, however, the influence of very short 1850 that a star which could not be found in duration is not to be neglected. MM. Richel its place was a planet outside the orbit of and Breguet have lately contrived an apparatus Neptune, but no searcher was ever successful in for giving very short flashes of light, in some |