RECENT TORPEDO EXPERIMENTS. the past and weeks Sheernes and Chatham have been the scenes of some important torpedo experiments. Last week a self-propelling submarine torpedo was tried at Sheerness, against the coal hulk "Aigle," with perfect success, smashing her starboard side in for a length of 26ft., and driving out the planking on the opposite side, as well as ripping up her deck. This torpedo is the invention of Mr. Whitehead, an English engineer resident at Fiume, and is the same as that referred to in our notice of the Austrian torpedo in the MECHANICS' MAGAZINE for Dec. 17, 1869. On Tuesday last at Chatham the stationary electrical torpedoes and their appliances, as proposed by the Royal Engineers for adoption for the defence of our ports and harbours, were experimentally tested. A small torpedo was practised upon to show the action of the floating contactmaker, and a large one was fired to illustrate the practicability of exploding submarine torpedoes at will, and of testing the limits of proximity within which such weapons could be placed in respect to each other without the explosion of one damaging its neighbours. The practice proved that a distance of over 100ft. was required to preserve adjacent torpedoes from damage by the exploded one. It was afterwards shown how torpedoes could be fired under ships by the intersection of two lines of sight taken by two observers, placed some distance apart. The experiments were most successful, the results demonstrating that a submarine torpedo can be fired at will, that it can be made harmless to a friendly vessel, and that it can be rendered fatal to an enemy. Pressure on our space obliges us to defer a description of the various torpedoes and apparatus, as well as the details of the practice, until next week. For the present we can only say that the torpedo service for coast and harbour defence has been brought to a pitch of high perfection by the Royal Engi neers. MACHINE FOR TWISTING METAL AUGERS, ESSRS. MACDERMOTT and WILLIAMS, of MKensington, propose to form the spiral twist upon metal bars or rods by mechanical means WHARTON'S TOBACCO SPINNING the bearing of the short roller N. Above and be-tween the rollers N and J is a revolving brush Q, actuated by a side stud in the pinion K. The front short roller is fixed on to R, a swivelling beam rocking on the bearings of the long roller J, and which is kept in position by the spring S, which is fixed on the head of an upright standard T. U is a fixed standard on the rocking beam. with curved head, V is a link to which is connected an adjusting screw W, which connects it with the spring S, on the outer end of which is a short link-rod connecting the outer end of the spring S with two compound levers Y and Y1. To the axle is connected a rocking arm and a pointer Z travelling over and under the scale. A step cone pulley a is fitted loosely on to the driving shaft b, on which is keyed a friction plate d faced with leather on the surface next to the cone pulley a, which is kept to the friction plate d HE Factory Act has made itself felt in our led to the invention of machinery to supersede into a second bevel wheel H on the end of a long manual labour in some portions of the manufacture roller, which revolves obliquely across the drum in which children were formerly employed. We B. A stud wheel K gears into the pinion L on especially allude to tobacco spinning, in which the shaft of the short roller. M is the spindle department, until the last year or two, no attempt which gives motion to the short roller N, which had been made to introduce machinery to supple- is partially covered by P, a metal guard fixed on Tlarge tobacco factories and its operation has the reverse end is keyed a bevel wheel d, gearing by the screw nut A tooth pinion ƒ on the first driving shaft b gears into s, a tooth wheel on the outer end of the second driving shaft F, which gives motion to the large drum B through the toothed wheel D, and through bevel gear G actuates the long roller J. A circular brush h is fixed on the axle of the first driving shaft b. of the curves. can thus be stoved, whilst the other presses are A PROPOSED RECOVERY OF THE the age. "CAPTAIN." The lever L will close the valve n of the steam exit orifice, and the steam will act with all its force upon the liquid within the receiver A. This liquid being thus placed between two equal and elastic forces i will cause (in consequence of the difference in level between the apparatus and boiler) the water inlet flow into the boiler; the float B will descend more and more; and for the effort upwards lately exercised will be substituted an effort acting downwards due to the weight of the float. At a certain moment this effort will be capable of raising the steam exit valve n, which was kept shut by the interior pressure of the receiver. At this moment this valvo will open, while the one m beneath the steam entry orifice will close. The steam finding it has a free escape, the water exit valve P pressed by the water in the boiler will close, and the water entry valve q again acted upon by the charge of water on the vacuum within the receiver will open and the receiver will again be supplied with water until the float is sufficiently raised to open the stop valve m beneath the steam entry orifice. The water contained in the receiver A will therefore Bevel gearing and shafting are shown at i, j, and licited by the vacuum produced in the apparatus, it k, the latter having bearings at b and b1, and the follows that this water comes naturally to fill the outer end of which carries a smooth disc or cam receiver A. This filling continues so long as the valves m and n within the steam apparatus are in wheel m, having a notch in the periphery and at one side. In line with it is a projecting tooth, the position shown in the engraving, but in proportion which at each revolution gears into one of a set of as the water rises in the receiver, the float B becoming more and more submerged causes an upward studs springing at right angles from a stud pin n, effort to be exercised upon the lever L which actuwhich actuates the revolving knife p. The stud wheel n has a series of curves on its periphery to SUGGESTION has been started by Mr. G. ates the steam valves. At a certain moment this prevent its turning round except when the same Featherstone Griffin, C.E., of Great George-effort, neutralised by the pressure exercised by the steam upon the valve m in the steam apparatus will coincides, and is allowed to escape as the indenta-street, Westminster, to recover the hull of the ill-be capable of raising this valve, which will immetion in the disc wheel comes round to the points the very strength of the vessel will perfectly en- attain the extremity of its course. fated ship "Captain." Mr. Griffin argues that diately open. The float being no longer held will The shaft k with its gear is used for cutting the able her to be raised bodily, after which her faults can be repaired, and at a comparatively small cost stick tobacco into lengths when the flyer and reel she can be rendered a monument of the science of are not used, but when the latter are used, the Mr. Griffin does not propose any special former arrangement is removed. When the cutting method of effecting his object, but he observes apparatus is used, the flyer is held stationary by a that the modus operandi will depend upon cirset screw in the bearing. q is an inner bearing cumstances easily ascertainable, and he recom- valve p to open, and the water outlet valve 7 to close. for the shaft b, r and s bevel wheels, the latter mends immediate steps being taken to mark the being keyed into the flyer neck t. u is the flyer spot, and if possible to grapple the ship itself, and and va sun wheel on the end of w, a reel which to make such observations as will enable the takes up the spun tobacco. The sun wheel gears necessary appliances for raising her to be preinto a planet wheel , which is fixed into a worm pared. Giving Mr. Griffin every credit for originatshaft y, working through a tubular stud z. A ing the proposition, and fully agreeing with him worm wheel a is fixed on an axle which projects that the raising of the "Captain" is an engineerthrough a hollow T bearing b; cis a slotted cranking feat not incapable of accomplishment, we have arm, to which is attached a connecting rod d, yet to learn what practical or beneficial end would which gives motion to e, a reciprocating carriage, be served were the end gained. If the " Capon which are mounted grooved anti-friction pulleys tain" were raised and repaired and set afloat f fl over which the spun tobacco travels, and is again she would require officers and men, and we evenly laid on the recl. The pulley f is mounted fear that nearly all who had any confidence in on a swivelling arm, allowing the pulley to accom- her have perished with her. Assuming she were modate itself to the increasing diameter, as the fully manned the great probability is that she tobacco fills on the reel. A grooved anti-friction would only find her way to the bottom again, unguide pulley g is mounted in the flyer neck. The less she were so altered as to be no longer the shown in fig. 4, an upper receiver c with its valve carriage e travels over h, a horizontal arm springCaptain" she was when she foundered. But which are used in other cases are suppressed. ing from a swan neck attached to the periphery of are we sure that we should raise a hull worth In order that the float may exercise as equal as the flyer u, extending across the reel parallel to anything at all, save the price of old iron, if even possible an effort in its upward and downward moveThe carriage is held in position by two that? She now lies in about 120 fathoms of water, counterweight placed at the smaller arm of the ments it is partially equilibrated by means of a pairs of grooved wheels, which clip the edge of the and the ocean pressure at that depth is some-lever L fixed itself upon the axis and traversing bed h; i is a grooved friction pulley on the end When we remember the receiver through a stuffing box. The smaller of the reel w, j a grooved friction band, that she was built with a double skin, which was thing very considerable. arm is prolonged on the other side of the axis in over which lays k, a friction band, one end of airtight, we shall realise something of the effect of order to command, by means of a connecting link which is attached to ma lateral arm springing the pressure upon her framing. Then, again, there and a notched lever, a counter or register E fixed from n a weighted lever, which has its fulcrum at were other compartments in her, which were made upon the apparatus and serving to indicate the numP, on the end of qa shaft, on which the lever is watertight, all subject to enormous pressure from ber of times the receiver A is filled and emptied. capable of adjustment within the frame, the outer the water, and there were also her boilers, which end of which is supported by the bracket r. A second arm s is fixed on the side of the weighted from the fearful collapse which must have enmust be in a worse condition than any other part lever n, to which one end of the friction strap sued. Altogether it seems to us that time, is connected. t is a sliding weight, u and ul a money, and brains would be thrown away in raising pair of spacing blocks for keeping the reel in posi- the vessel, and as it is not desirable to perpetuate tion; by removing one, the reel is thrown out of the race of "Captains we think she had better gear, and by removing both, the reel can be with-rest quietly at the bottom of the ocean where an untimely fate has placed her. Were the attempt to be made to raise her it must be made from the surface, and with mochanical appliances worked from that point, as the assistance of divers is out of the question at such a depth of water as she lies in. Were she in 25 fathoms of water only divers could materially assist in the operation, but not much beyond that depth, 27 or 28 fathoms being the greatest depth ever yet attained by any diver. Therefore, unless Mr. Griffin can show better reasons for raising the "Captain" than we have advanced against that operation, our decided opinion is that the proposition and ship should both be allowed to remain where they are. its axis. drawn. manner. SELF-ACTING WATER FEEDERS FOR HE When water is taken from an upper reservoir as The float B is of elongated form in order that its displacement within the receiver may vary as little as possible the strength of the efforts exercised by it in the two opposite directions. The above effects will continue so long as the pipe a, fig. 4, which of the water in the boiler. When the lower orifice leads the steam into the apparatus, is above the level of this pipe is submerged the water of the boiler will fill it, the receiver A being only able to empty when the steam is able to come and manifest its pressure. The lower orifice of this pipe a is provided with a cup or strainer (cuisine) perforated with small holes which lessen the agitation of the water at the first moment after the equilibrium is broken. When the feed water is heated to a temperature above 195deg. to 200deg. Fah. (80deg. to 85deg. Centigrade) the feeding can only be accomplished this case the apparatus is arranged as follows:-A when the water is in readiness for charging. In reservoir R placed above the rest of the apparatus contains the water for feeding. A pipe T which traverses it serves to heat this water by the escape steam from the machine, which finds an issue through a vent pipe T, after having passed round the two sides of a partition placed for the purpose within the reservoir. The hot water can be drawn from a lower reservoir if the apparatus is situated near to a condensing machine. In such a case the pipe 5 for the emission of steam is put in communication with the air pump of the machine to determine the vacuum within the receiver A. The pipe leading to the boiler, prolonged to the water level in the latter, serves, as above stated, to conduct the steam. It is plunged for an inch or two into the water in the reservoir R, so as render up to the liquid therein the caloric of the escape steam. In manufacturing twisted tobacco by means of this apparatus, the leaf is prepared in the ordinary The tobacco forming the filling of the roll or twist is supplied to the trough in front of the long fluted roller and inmediately over the travelling apron. The action of the roller and the apron slightly twists the tobacco, which is carried obliquely on to the periphery of the drum wheel. Passing between the two pressing rolls it takes up the wrappers, which being spread out on the face of the dram wheel, are carried forward under the short pressing roller. By the joint action of the pressing rollers and drum the wrappers are tightly folded spirally round the filling. The material passes thence through the flyer neck on to the take up recl, if for twist, but if for roll or stick tobacco, into the guide, where it is cut off by the reciprocating knife into the required lengths. In making stick tobacco, the twist is delivered into a trough, along which it travels to the desired dangers arising from the lowness of the water in steam boilers have led the engineers length, when it is cut off by the knife, the trough of this and other countries to devise some means by tilting at each cut, and discharging its contents which the proper level shall be maintained at all into a reservoir. The tobacco is finished and pre- times notwithstanding the pressure of the steam. pared for market in a stoving press, specially de- Among the most recent inventions of that class is signed by Mr. Wharton, and which may be used one patented by Mr. P. N. J. Macabies, of Paris. either hot or cold. This press consists of a vertical The apparatus is composed of a receiver A containdouble-sided chamber, having steam supplied to it ing a float B, which actuates the organs which affect is cold, the apparatus can draw the water from a at a pressure of about 16lb. per square inch- the distribution of the steam by means of a lever L lower level; but it is necessary, in this case, to probetween the inner and outer casings, which are of acting upon either a system of valves or a sliding vide it with certain supplementary organs intended valve, as may be found preferable in practice. This to condense the escape steam. In the latter case, cylindrical form, the inner one being of a diameter sliding valve or the valves permit the alternate inlet the feed, properly so called, is surmounted by a sufficient to receive the largest roll of spun to- and exit of the steam into the receiver. Accord- supplementary receiver C, with which it is in commubacco. The lower end of the stove rests on an open ing to the arrangement shown in fig. 1, the steam nication by means of a valve box. framing fitted with a vertical rising screw, carry-enters the apparatus through an orifice a, and leaves escape pipe enters at the top of this supplementary ing a platten and a stout sliding plate to receive through another orifice b. The water enters the receiver C. When the escape takes place the water the screw thrust. The rolls of tobacco to be stoved inlet valve opens and the valve of the valve box are placed between loose plates of metal, so that closes. The water contained in the supplementary on the withdrawal of the thrust plate they can be receiver C, by virtue of the difference in levels, flows lowered on to the platten on the head of the into the receiver A and condenses the steam therein. The vacuum is caused at this instant the two screw, and on returning the thrust plate, the revalves r and a last spoken of solicited by the vacuum quired pressure can be given to the tobacco. The open, and the water being thus drawn up enters the steam-tight casing is removable from off the press, two receivers A and C. so that it is made available for surrounding several presses in succession. The tobacco in one press receiver A through an orifice e provided with valves q, If the feed water is lukewarm, or better still if it The steam When 'the receiver pipe A is full, and the float changes the position of the valves m and n of the SELF-ACTING WATER FEEDERS FOR as shown at fig. 3. In this case, it will be neces- steam apparatus or of the sliding valve, the steam movement of a toothed sector T mounted on the on between two great European nations creates a strong desire on our part to make the public acquainted with the description of arm used by either side in the contest. We have in our pages already detailed and illustrated the French Chassepot and the Prussian needle guns, and now illustrate what is known in Bavaria as the Werder, and with which the troops of that kingdom are armed. The block is somewhat like a Snider, only much shorter; it is hinged on lugs at one side, so that it can be lifted and thrown over to open the breech by means of a lump projecting from the other. The hammer rises through an For machines of large dimensions these valves may be replaced by a distribution slide, acting as shown in fig. 3. This slide enclosed in a steam The apparatus deprived of the condensing receiver box M is actuated directly from the interior of the e can draw the water by means of a serpentine pipe receiver A by the lever L of the float, bent at immersed in the receiving reservoir, and terminated the place of the axis (see fig. 3). One orifice a serves by a valve opening both ways. This serpentine pipe for the entry of steam, and another 6 for its exit. will be in communication with the steam escape In this arrangement, it is necessary to have, in addi-opening in the top of the tang, similar to the Engpipe b. The steam will escape first into the reser- tion to the counterweight, which serves to equili-lish Soper, and acts upon the stem of the striker voir by its excess of pressure, and what remains at brate the float, a second counterweight h, which the atmospheric pressure will condense and deter-assists the first and serves radically to break the mine the vacuum in the apparatus. In consequence equilibrium. of this, air can never remain in the feeder. The employment of non-equilibrated valve does not permit the precise measurement of the quantity of water introduced into the apparatus, since the receiver will be more or less completely filled, according as the pressure of steam is more or less strong. When it is desired to take count exactly of the quantity of water introduced, these valves are replaced by a system of equilibrated valves, arranged OWENS College, Manchester, has lately received a very valuable donation to its large geological collection, in the shape of a collection of fossil Marsupials from Australia. This collection was to have been presented to the British Museum, but the donor ultimately decided to bestow it on Manchester instead. at the centre of the block, to ignite the charge. There is a projection on the extractor, which is struck sharply by the lip of the block when the block is thrown over, so that the empty case is withdrawn from the chamber. In order to prevent escape of gas at the breech at the time of the explosion, the bottom face of the block is grooved, which grooves take over ribs on the top face of the box, and thus divert the gases from the face of the soldier, should there be an escape from a faulty cartridge. THE WERDER (BAVARIAN) RIFLE. FIG. 1. FIG. 2. The nipple through which the striker stem projects is provided with a lip, and the nose of the hammer in coming down upon the striker engages itself thereon, and holds the block secure while the explosion takes place. The construction of the rifle will be well understood by referring to the engravings, where fig. 1 shows the breech portion, with the block thrown over to expose the bore ready to receive a cartridge, while fig. 2 shows the block closed and the hammer on the nipple. The other portions of the arm are of the ordinary construction. It will be seen that the back force of the explosion is received by the two cheeks against which the block rests when closed down. A LUMINOUS METEORS. FEW months since we made some observations upon meteorites, giving the opinions of philosophers who had investigated them as to their origin, such opinions being formed from the inspection of various meteoric masses which have fallen upon the earth from time to time. We now propose to advance a few remarks upon a similar yet dissimilar class of visitants to our regions-luminous meteors: similar as visiting us somewhat irregularly and coming from the unknown regions of space, dissimilar as being intangible and appreciable only to sight. We have of lato had several aerial visitors of this class, notably two of extraordinary size and appearance, which appeared on the 15th and 20th of last August. That month is generally noted for the appearance of what are popularly known as shooting stars, but these displays usually occur on the nights of the 9th, 10th, and 11th, whereas the two meteors above referred to came the one four, and the other nine days-or rather nights-later. The first and lesser of these two visitors was remarkable for the manner in which it faded out of sight. It was specially observed by a clergyman at Broughton-in-Furness, and by the Duke of Argyll at Inverary, and it appeared in the N.N.W. regions. The time of its appearance was about half-past nine, the sky being at the time cloudless and tinted with the after-glow of a clear sunset, which served to diminish the luminous effect of the meteor. Its first appearance was that of a large star, which soon apparently burst or exploded. A tail of about 5deg. in length depended from it to the earth, but gradually rose to the westward till to one observer it was horizontal. This tail remained in view for several minutes and at last slowly faded away. The Duke of Argyll in writing of this phenomenon alludes to it as a very remarkable meteor, its great peculiarity being the appearance presented by the luminous vapour which was the product of its explosion. This vapour was brighter than the tail of any comet, and after being at first of a linear shape it assumed a curved or horseshoe form. It then drifted away in a south-westerly direction, as if under the influence of a north-west wind, which was blowing at the time. This remarkable appearance was quite distinct from the class of ordinary shooting stars, inasmuch as it remained visible for a long time-some fifteen minutes elapsing between the explosion and final disappearance of the luminous train. the phenomenon as appearing in the N.N.W., at an angle of about 30deg. above the horizon. He further states that it descended at an acute angle from left to right with a luminous train in its wake, which was afterwards drawn up into the form of an ellipse, and after being visible for seven or eight minutes faded away. Now with regard to the angles of elevation they are doubtless inaccurate, but let us take them as they stand and see where they will place the phenomenon. The distance from Broughton-in-Furness to Inverary is about 200 miles, and taking the angle of 25deg. at Broughton and 50deg. at Inverary, the meteor would be in a vertical position over the island of Lewis-that is, 130 miles N.N.W. of Inverary, and 160 miles above the surface of the earth. If we take the third observer's angle of 30deg. at Inverary, and work it in with that of 25deg. at Broughton, we find that the meteor becomes vertical at a distance of 800 miles from Inverary, its altitude being 500 miles above the earth, which is clearly an extravagant result. The second of the two meteors, it will be remembered, appeared on August 20 at nearly the same hour as the previous one, namely, about twenty minutes past nine in the evening. It was highly luminous, its brilliancy being such as to cast an effulgence resembling a flood of day over the country around. As observed at Woodstock the meteor appeared to fall vertically from a point somewhat eastward of the zenith, assuming the appearance of a ball of white light and being about half the apparent size of the full moon. It was slow in its movement, and burst in its descent, but without scattering any sparks. This meteor was also observed from Linton, in Cambridgeshire, 75 miles off, in a direction about E.N.E. At Linton, however, it appeared to be travelling in a direction nearly from west to east, and somewhat to the north of the zenith. The Woodstock observer, doubtless saw the meteor in a direction more or less easterly, for he describes it as apparently falling only a field or two distant in an easterly direction. The fact, however, is that there were more than 75 miles between this observer and the disappearing point of the meteor. Both observers agree in attributing to the body a diameter equal to half that of the full moon. The one at Linton, however, ascribes to it a quicker motion than it appeared to have at Woodstock, and to him it appears to have been more distinctly defined, showing that the phenomenon was nearer to Linton than to Woodstock. If it was really in the zenith of the former place and visible at the latter at an angle of 45deg., its height from the earth would be equal to the distance between the two places. If we place the meteor as vertical to the east of Linton we thereby increase the miles of altitude, and so also if we raise it up higher towards the zenith of Woodstock. The probability is that its true position was vertical to the east of Linton. An observer at Toddington, Beds, saw the meteor high in the sky, and falling perpendicularly; he describes its appearance as that of a ball of metal at a white heat. As it continued to descend it showed nearly all the colours of the rainbow, and became oval in form as it disappeared nearly due east about 15deg. or 20deg. above the horizon. He did not see it burst, neither did he observe any sparks fall fro'n it, nor any trail left behind in its course. No On August 28 another meteor of large size-although smaller than either of the precedingwas seen at Brigg, in Lincolnshire, and also at Bushey, Watford. It is described as illuminating Bushey and travelling rapidly in a north-westerly direction, finally bursting into six stars, three being of a green colour and three white. sound of explosion was heard, and the duration of appearance was about four seconds. The information respecting these bodies is extremely vague and meagre, and there is much with reference to them which yet requires explanation. There are many indefatigable workers in meteorological science who would doubtless be glad to add to the scant knowledge we possess on the subject, and accurate scientific observations would be peculiarly valuable. But the more remarkable of our meteors rarely appear at such times as observers are prepared to give them their attention. Hence we have to make the best we can of the evidence afforded by willing but less learned witnesses of their appearance. Mr. Alexander The exact position in the heavens of this visitor Herschel has calculated that the range of elevaappears to be by no means certain; the Lanca- tion possessed by meteors lies between 16 and shire observer gives the altitude as 25deg., whilst 140 miles. The velocity with which they travel the Duke of Argyll gives it as 50deg. Another is computed at 18 miles per second and upwards, Scotch observer, also in Argyllshire, describes or from 60 to 120 times the velocity of the swiftest projectiles. Another point requiring attention is the combustion of bodies at an altitude of 80 miles above the earth's surface. The air at such a height must be more attenuated than the atmospheric contents of an exhausted receiver. The intensity of the combustion of those meteoric bodies (if they are bodies in a state of combustion) may be inferred from appearances such as those observed at Linton and Woodstock, the light being sufficiently powerful to illuminate objects for a great distance around. From Woodstock the meteor was probably distant some 70 or 80 miles, or even more, yet the light was extremely vivid, whilst at Linton every object was at once illuminated as if by a flash of lightning. PORTLAND CEMENT. we lately visited these materials are brought in barges from a short distance and deposited in T is difficult to define with certainty the source heaps in the yard; they are wheeled from thence from which Portland cement derived its name; to the wash-mills as necessity requires. These notwithstanding the many excellent treatises that mills are of simple construction; each has a cirhave from time to time appeared, its early history cular pan 6ft. in diameter and 2ft. deep, in which is to some extent involved in obscurity. It is pro-two edge runners," 4ft. 6in. in diameter, are bable, however, that Portland cement was so called kept continually going; a constant stream of from a presumed resemblance which it bore, when water flows into the pan, and as the "edge first introduced, to the colour of Portland stone; runners" revolve the chalk and clay are thoat all events, we can assign no more plausible roughly ground, and, being thus converted into a reason for its nomenclature. fluid state, they filter through a band of fine brass Portland cement is undoubtedly of English wire gauze fixed to the side of the pan, and flow origin. It was introduced to public notice under through wooden "launders " into tanks or settling a patent by an Englishman nearly fifty years ago; reservoirs. One wash-mill will feed four tanks, each It is argued by some that this meteor was we have hitherto possessed a partial monopoly in of which is about 100ft. long, 40ft. broad, and 4ft. something less evanescent than lightning, inas- its production, inasmuch as we have, fortunately, deep; when one of these has been filled in the much as it sailed steadily but rapidly on its way. inexhaustible beds of the raw material from which manner just described the same process is applied The original white light passed through the it is made, and an abundant supply of fuel neces-to the others in succession. About three weeks phases of violet, pink, and crimson, until it faded sary for their economical manufacture. It is after the tanks have been filled the whole of the out with a delicate green colour, some dull strange that under these conditions French en- materials will have been precipitated, the clear reddish sparks lingering for a few seconds after-gineers should have obtained the start of their water having been drained off in the meantime wards. It is possible, however, that these pheno- professional confreres in this country, and that through a small weir in the brick side of the tank; mena are attributable to electrical agencies if they should have been the first to demonstrate by the residuum is a plastic mixture of the consistthey are not themselves direct manifestations of experiments, and, subsequently, by the erection ency of "putty," and not much unlike it in colour. electricity. There are, as is well known, light- of magnificent harbour works on their seaboard, The next process is to convey this precipitate in ning flashes which appear in the form of globes the valuable properties of this excellent construc-wheelbarrows from the tank to the "drying of fire, which are sometimes invisible for as much tive material. We may date the extensive em- floors," over which it is spread in a layer of about as ten seconds. They descend from the clouds to ployment of Portland cement in England from the Gin. thick. Each floor is 40ft. by 30ft.; it conthe earth with such slowness that the eye can commencement of the metropolitan main drainage sists of an outer skin of boiler plates resting follow them, and often rebound on reaching the works. The experiments conducted by Mr. Grant on a series of brick ovens and flues. The ground. At other times they burst with a loud and others have happily been instrumental in dis-object of this arrangement is to render the report. About twenty years since we ourselves pelling the mistrust with which it was previously plates sufficiently hot to effect the rapid desicwere in close proximity to one of these globular regarded by English engineers; and we are now cation of the water from the superincumbent flashes, which was discharged from a thunder no longer open to the reproach of allowing layer, a process generally accomplished in about cloud travelling at a comparatively slow speed to foreigners to show us what can be done with a twelve hours. The materials having thus been the earth, at an angle of about 35deg. It struck material of which we are ourselves the principal thoroughly dried are ready for conveyance to the the cornice of a house at a height of about 40ft. producers. During the last fifteen years the manu-kilns. Mr. Reed accurately describes in a few from the ground, and at a distance of some 60ft. facture of Portland cement has gone on steadily words the theory of "burning" cement; he says from the point where we were. It burst with a increasing, until at the present day we find that" that as in lime making, the object of burning is loud sharp report, ripping down a large extent of little short of 400,000 tons per annum are made in to set free the carbonic acid in combination with cornice, and spreading out a radial or fan-like the county of Kent-the centre of cement manu- the materials, so also in manufacturing Portland flash, which struck us across the chest. The force facture-irrespective of the productions of many cement sufficient heat is required, not only for the of the electric current was strongly, though not minor factors in different parts of the country, same purpose, but also to facilitate the partial vipainfully, apparent, leaving a sensation still re- Fully three-fifths of the total quantity are used trification of the mixture." In a notice of this kind membered and not wished for again. But the by English engineers, either at home or abroad. we need not enter into a detailed description of the luminous meteors we have been considering are We still continue to supply large quantities to the kiln; it will be sufficient to state that the one we saw at great altitudes, and it may be said that neither French, and a new market has recently sprung in use is of a circular form, 16ft. in diameter and in speed, duration, nor result do they in any way up through the demands of Russia for the exten- 25ft. high; it has a dome-shaped top, with an orifice resemble the globular flashes of electricity. It sive public works now being carried out there, for the escape of the carbonic acid gas; the must not, however, be forgotten that the very fact The chemistry of the setting of Portland cement" charge" consists of alternate layers of coke and of the great altitude would render a very rapid is by no means so well understood as it ought to raw materials, the burning generally occupying motion apparently slow, and that meeting with be. There is no doubt, however, that, like the thirty-six hours. When the contents of the kiln little or no resistance their duration was pro- hydraulic lime and natural cements, it is, chemi- become sufficiently cool, the "clinkers," or longed as compared with that of those which pass cally speaking, a double silicate of lime and alu- cement stones-for the mixture has now assumed through the atmosphere to earth. Then with mina; silicic acid is generated by the hydration of that form-are drawn and removed to a floor regard to form, we know that in electrical experi- the cement, and forms insoluble salts with the lime where the larger pieces are broken, and the whole ments when the discharge of a large jar is effected and alumina bases. It is a curious fact that Port- of the burnt materials are then conveyed to the through a tube filled with rarified air it appears land cement hardens more rapidly when salt water hoppers of the grinding-mills, where, passing luminous and in a condensed form, like a ball of is employed. May not this arise from the follow-under rapidly revolving horizontal burr-stones, fire falling through the tube. To account for the ing causes?-According to Schwertzer, 1,000 they are ground into an almost impalpable powder. colour we have only to remember the changing grains of sea water in the English Channel con- The cement issues from the mill at a temperature colours of stars, as seen through our atmosphere, tain 27-060 grains of chloride of sodium; soluble of about 160deg., and the now manufactured maor the appearance of the Aurora Borealis, which silica has a known preference for alkaline bases, depends, most probably, on the passage of electri- and it is not improbable, when the cement is city through a highly rarified medium. But to hyrated with sea water, that the chloride of arrive at a definite knowledge of these remarkable sodium is decomposed, the silicic acid of the cebodies some further observation of them is re- ment combining with the sodium and oxygen of quired. It is, therefore, to be hoped that as regu- the water, and forming thereby a silicate of soda, lar observers are not always prepared to notice or a species of crude glass. To this cause we them such persons as see them should publish in attribute the more rapid hardening when salt the papers as correct an account as they can of water is present. their observations. By doing this they will be aiding scientific deductions in determining the nature and character of luminous meteors. S "best terial is wheeled away, and spread in a layer from 2ft. to 3ft. thick over the floor of a cool shed, where it is subsequently packed in casks or sacks for conveyance from the works. We may summarise the essential conditions for the manufacture of good Portland thus: (1) The chalk and clay should be thoroughly mixed in the wash-mills, and the fluid materials delivered by "launders" over the entire area of the settling tanks. (2) The contents of the kilns ought to be burnt equally throughout. (3) The burnt materials should be ground very fine. (4) After coming from the mill the cement should be spread over the floor of a shed, and allowed to remain there for at least a fortnight previously to being packed into casks or sacks. Having now briefly, and, we fear, incompletely, sketched the different processes, from the delivery of the chalk and clay in the yard to their manufacture into marketable Portland cement, we purpose concluding our remarks with We purpose dealing now with the manufacture of the cement, but before doing so we ought to state that marketable Portland cement is of two classes, which, for the sake of distinction, may be termed "engineers'" cement and "plasterers'" IMPROVEMENTS IN PIANOFORTES. cement. The former is the more costly; it is OME remarkably fine instruments have been usually described by manufacturers as lately brought out by the well-known firm heavy tested"; it weighs from 1121b. to 1201b. to of Messrs. Hund and Son, of Ebury-street, Pimlico, the bushel, is slow setting, and of great strength; whose experience in the manufacturing of piano- the latter is a light cement, quick setting, and of fortes has extended over a quarter of a century. The inferior strength when compared with the other. principal feature of these instruments is the adop-It must be understood that our remarks apply ex-a few observations of a more general character. tion (with improvements and modifcations) of clusively to "engineers'" cement; we prefer to the American system of iron framework, which say nothing here of the other questionable comadds great strength and durability to the instru- pound. Having thus generalised the two disments and renders them less liable to the variations tinct types, we will proceed to describe the manuof the temperature, and therefore will keep in tune facture." in almost any climate. To shippers this is an all- Portland cement is made from chalk and alluvial important point, as in many cases instruments clay; the factories on the banks of the Thames manufactured in our climate are entirely unfit for use white chalk, those on the Medway grey chalk, another. The instruments referred to possess a the latter is probably preferable, inasmuch as it It appears from Mr. Grant's valuable paper, purity of tone, elasticity of touch, equality of sound, contains large quantities of silicious matter. Mr. read before the Institution of Civil Engineers in and that peculiar singing quality that is so much Reed, in his invaluable treatise on Portland cement, December, 1865, that Portland cement gains from sought after by pianists, and which so much distin- says, that "the present and safest proportions, 20 to 30 per cent. in strength by setting under guish American pianos. Amateurs and professors can provided both chalk and clay are selected free water; it is usual, therefore, to place the test satisfy themselves as to the quality and soundness from sand, are four parts of chalk from the Med-briquettes in water, after gauging, and to allow of workmanship of these instruments by visiting way (grey), or three parts of Thames (white), them to remain there until they are to be tested. the factory of Messrs. Hund at any time. with one of clay by measure." In the manufactory The following table brs been compiled from a The strength of Portland cement increases as its specific gravity increases; the tensile tests are usually made with briquettes, the standard size for the neck being 1in. by 14in.; and it must be understood that all experiments referred to by us have reference to the weight necessary to sever 2 square inches of neat cement. |