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used ind discarded a gas engiae.and now has one of Sir William Armstrong's hydraulic engines of ordinary construction. Tbis looks тегу big and clomsy, and the workmanship i« not first-rate. It possesses also the additional disadvantage oí running at а тегу slow speed. Altogether we ■bould have thought a small Inrbine preferable, and failing that, a steam engine with a boiler h«ited by gas. Of course when tie lathe is being drirea by a belt, the treadle crank is unhooied.

The leading- screw is driven hv a bright set of engine cat change wheels; and from this screw Tarions motions are got for the otber movements of ihe slide rest, which is self-acting on the longitudinal or traversing, the traverse or surfacing, the angular and the curvilinear cats. These motions, it will be seen, are all contained in a very small space; and the neatness of contrivance indicates the posjession of considerable ingenuity on the part of the designer.

Thescrew headatock has the base slide arrangement for setting ont of centre when taper turning, and the usual pinching arrangement at the sido /or holding the spindle fast, and preventing shake. Tbe eoae spindle is shown with the compound eccentric chuck on its nose. It has a large division-plate completely divided ; tangent and screw motion for slow rotation; and another arrangement at the side for slow traversing.

The overhead apparatus is very compact and convenient. Its whole arrangement is, however so plainly shown by our illustrations, that a description is scarcely necessary.

MECHANICAL MOVEMENTS.»

(Continued from page 28.)

~i А о infirmai rotation of the pinion (ob

-» • tained through the irregular-shaped gear at

íbe left, gives a variable vibrating movement to

the horizontal arm, and a variable reciprocating

movement to the rod, A.

2. Worm or endless screw and wormwhee]. Used when steadiness or great power is required.

3. A regular vibrating movement of the curved Blotted arm gives a variable vibration to the straight arm.

4. An illustration of the transmission of rotary motion from one shaft to another, arranged ob. liqnely to it, by means of rolling contact

• Extracted from a compilation by Mr. il. J. Brown, bailor of the American Artisan.

MECHANICAL MOVEMENTS.

5. Represents a wheel driven by a pinion of two teeth. The pinion consists in reality of two earns, which gear with two distinct series of teeth on opposite sides of the wheol, the teeth of one series alternating iu position with those of the other.

6. A continuous circular movement of the ratchet-wheel, produced by the vibration of the lever carrying two pawls, one of which engages the ratchet-teeth in rising and the other iu falling.

7. A modification of No. 10, shown lest week, by means of twe worms and worm-wheels.

8. A pin-wheel and slotted pinion, by which three changes of speed can be obtained. There are three circles of pins of equal distance on the face of the pin-wheel, and by shifting the sbtted pinion along its shaft, to bring it in contact with one or the other of the circles of pins, a continuous rotary motion of the wheel is made to produce three changes of speed of the pinion, or rice versa.

9. Represents a mode of obtaining motion from rolling contact. The teeth ore for making the motion continuous, or it would cease at the point of contact shown in the figure. The forked catch is to guide the teeth into propor contact.

10. By turning the shaft carrying the curved slotted arm, a rectilinear motion of variable velocity is given to the vertical bar,

11. A continuous rotary motion of tho large wheel gives an intermittent rotary motion to the pinion-shaft. The part of the pinion shown next tho wheel is cut of the same curve as the plain portion of the circumference of the wheel, and therefore serves as a lock while the wheel makes a part of a revolution, and until the pin upon the »heel strikes the guide-piece upon the pinion, when the pinion-shaft commences another revolution.

12. What is called the "Geneva-stop," used in Swiss watches to limit the number of revolutions in winding-up; the convex curved part a ft of the wheel В serving as the etop.

13. Another kind of stop for the same purpose. 14 and 15. Other modifications of tho stop, the

operations of which will be easily understood by a comparison with 12.

(7b be continued.')

THE PEO E SPEED.

{Illustrated on page 61.)

A FEW mornings since, says the Scientific Cjl American, a quiet gentleman and a handsome youth walked into our sanctum, bringing with them a queer-looking package. While the

elder of the two gentlemen entered into conversation with us, the younger undid tbe package, disclosing a pair of wheels some fourteen or fifteen inches in diameter, to which were attached some stout hickory stirrup-like appendages, iu the bottoms of which were foot pieces, shaped like the woods of common skates.

On one side of the stirrup-like appendages were firmly fastened metallic plates, each having а short axle or bearing projecting from its centre, upon which the wheels above-mentioned turned. The stirrup-like appendages were made of flat strips of wood about three inches wide in the broadest portion, bent so that one side was nearly straight, while the other was made to meet it about midway to form a sort of loop. In the bottom of this loop were placed the foot-pieces above described, provided with toe straps and a clasp for the heel. To the upper end of the stirrups was attached a piece of wood to fit the outer and upper conformation of the calves of the legs.

In less time than it took us to note these points the young gentlotnan—who was subsequently introduced to us as tho son of the inventor of this singular device—had strapped on the wheels and commencod rapidly gliding about among chairs and tables with eingal ir swiftness and gracefulness. Л space being cleared he proceeded to execute with seemingly perfect ease, the inside and outside roll, figure of eight, &c. &c, amply demonstrating that the "pedespeed" hue all the capabilities of the skate, both in the variety and grace of the evolutions that can be performed with it.

Our engraving gives an excellent representation of this invention. Of course no mere carpet knight accustomed to roll about on the common parlour skate, can nse these at the first attempt. They require practice ; but when skill is once attained, there is skating the year round. Had Ae "pedespeed " been introduced on our rinks this winter during the long period stockholders have prayed in vain for ice, their stock would have stood higher in the market than it does at present.

The " pedespeed " is light and strong, and is capable of use on surfaces where the ordinary parlour skate vould be useless. The inventor, a large and heavy man, informs ич he can use it constantly for two hours without fatigue. For gymnasiums, colleges, and parts of the country where no ice ever occurs, it affords a delightful, healthful, and graceful pastime at all seasons of the year.

When used by ladies, shields may be employed to cover the top of the wheels, so as to protect tho dress.

SCIENCE J)'OR The Young.
Sebies I.—Mechanics.

INTBODUCTION.

By The Rev. E. Keenan.

THE object of these papers is to lay oat for the beginner in Mechanical and Physical science a course from which he will never require to deviate permanently, no matter to what extent circumstances may induce him in after years to increase his Bcientiflo acquirements.

For such an elementary course, however, no great mathematical knowledge is required ; the use of simple algebraical formula:, some geometry, and the first principles of trigonometry are, as the rule, enough. Where exceptions occur the means by which full satisfaction may be obtained later on can be indicated. Moreover, in many branches of science, the gpeat principles can be acquired scientifically, and yet simply, without that mathematical learning employed for their full theoretic development by the more advanced scholar.

Mechanics being the foundation of all true knowledge, claims the first place in a scientific course. The series on mechanics may be divided into three parts. The first sets forth some necessary preliminaries, which, once determined and understood, facilitate the work to come; the second contains all that is usually understood by mechanics in its widest sense ; the third treats of bodies in a state of vibration, practically sound, acoustics, which is so closely connected with mechanics that it can be shown to be contained in the definition of this science.

Part I.—Pbeliminabies.

These may be classed under three heads : The object of mechanics, with tho division of the subject -, the general properties of matter; and the explanation of terms required for study.

CHAPTER I.

OBJECT OF MECHANICS; DIVISION OF THE SUBJECT.

Before answering directly to the question, "What is mechanics? " it would be useful, if not even to a certain extent necessary, to say what it is not. First, then, mechanics is not the method of working in wood or in iron. They who are thus occupied are called "mechanics," but they are not thereby designated as having acquired the science of mechanics. Not but that they could possess it, and would profit much by a knowledge of its principles. Frequently their knowledge is but if mere routine of facts, handed from one to another, the cause of which they do not understand. The small amount of mind required to obtain knowledge of this class, and the fact that such knowledge is not unfrequently combined with great mental deficiency, are the reasons why the "mechanic " is not considered as having the higher gifts of intellect. Secondly, the science of mechanics is not che dull, dry study that some imagine.

It is quite true mechanics do not possess for some the interest which, for example, the brilliant experimental part of chemistry excites. But if so it has none of the dull, plodding, mere memory work of theoretical chemistry. Every proposition of mechanics sparkles with proof, mathematical and experimental. With a pencil and paper the thousand phenomena which may occur are discussed, and their cause, result of combination, &c, declared; the instruments are brought forward, and experiments prove the truth of the theory. Again, the constant occurrence within us and around us of the exemplification of meohnnical principles is a new source of interest to an intelligent mind. So far what mechanics is not. Now, on the other side, mechanics is that part of natural knowledge which best deserves the name of a "science." For its principles have, of all others, been put to the severest of tests—length of time, found as they are in the very first pages of the history of science ; extent of application, including, as they do, everything in the cosmic system that has as yet been brought into a really scientific form. And so strictly is this latter true, that the fundamental principles of mechanics are every day extending themselves to new branches, rendering clear and logical what was before but a collection of facts, without explanation other than obscurities or contradictions. Thus, from the principles of mechanics of solids

applied to the liquid state has arisen the science i.f hydrostatics and hydrodynamics; from their extension to the gaseous state has resulted tbe »cience of pneumatics. Passing to the confines of the ponderable world, to the connecting link between matter tangible an d untangible, sound is discovered to require no new principles. Reaching farther, to the region of what are usually termed imponderables, the principles of mechanics, have seized upon light, aud made it subject to their unerring laws. By this great conquest are explained phenomena most complicated and apparently contradictory, which had before been but an enigma. By it, without fear of error, it can be shown that in such and such conditions, certain extraordinary phenomena should be observed which reason would be inclined to reject as impossible or absurd; for instance—that two lights can be a cause of darkness. It is not surprising, then, to find Dr. Lloyd in his lectures on light, say of Fresnel, the French philosopher, who worked out the mechanical theory of light, that he has " reared the noblest fabric which has over adorned the domains of physical science— Newton's system of the universe alone excepted." Even beyond light has mechanical investigation progressed. Heat, less tangible, is being proved, every day, more and more, to be but its " mode of motion." The time is perhaps not far off when electricity shall cease to be that unknown mysterious agent, shall yield its secret to mechanics ; showing to the wise ones to what a distance from the truth they have wandered, how they have groped in tbe dark, wasting their energies in theory and speculation.

What, then, is this so much lauded mechanics? It may be differently defined, according to the point from which it is viewed. The following definition will suit the form of the present series: Meclmnics is the study of the laid which regulate the action of external forces upon all bodies. Bodies exist in some one of the three states, solid liquid or gaseous, and the student cannot begin too soon to keep this triple state of matter before his mind. That solids can be affected by forces requires no proof. For liquids it is only necessary to place a tray with water on a table ; the least stir ruffles it's surface; for gases, the rushing of the "thin air," tho winds, the storms supply superabundant proof. By the word external is to be understood some manifest action or effort at action; and this effort may be from the nature of the body itself, or from some external source. Thus is mechanical study distinguished from others in which action not directly manifest is the chief object: for instance, chemistry. The study of the laws includes not only the mere statement of them, but also the proofs of their truth, and their actual or possible existence in action, in natural or artificial combinations ; in a word, the applications of the principles contained in the laws.

(To be continued.)

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A GRAND ORGAN.

ATRIAL has been made of the tone of the grand organ which is being built for the Royal Albert Hall, at the works cf Mr. Willis, at Camden-town. This magnificient instrument is remarkable not only on account of its size and the number of its pipes, but also on account of the excellence of its design and construction. It is GSft. wide, 70ft. high, and 40ft. deep. It weighs over 150 tons, and has nearly 10,000 pipes in it. The largest pipes are 2ft. 6in. diameter—the smallest about a couple of inches long, and not much thicker than a barley straw. In all there are somo nine miles length of pipes of various sizes. There are no less than 138 stops, 20 couplings, and CO combination pedals and pistons. The extreme range of compass from the highest to the lowest notes is nine octaves apart. There are four sets of manual keys and one set of pedals. The manual keys extend from C i to o in altissimo, or sixty-one notes ; and the pedal from C С C to G, or thirty-two notes. The pedal organ consists of twenty-впе stops, the choir organ of twenty stops, the great organ of twenty-five stops, the swell organ of twenty five stops, the solo organ of twenty stops, and there are fourteen couplers. Eight pneumatic combination pistons govern the whole of the stops of each manual range of keys, and these are so placed below and in front of the keys as to be at all times within instant reach of the Lauds of the performer. Six pedals govern the stops of the pedal organ. The "Swell " is, as usual, in the rear of the organ, and will be in to

separate chamber, 20ft. by 20ft, and 20ft. h\ The key notes, or " claviers," as they are ttch^ cally called, are made of massive ivory, exquisitely balanced that the least touch i oient to sound them, and, in fact, notwithsn the size of the organ, any lady could play up< with the same ease and with the same rapidity as she could on a cottage piano. If anything, the notes are almost too easily sounded, and ecaroáy give that rest for the hand to which organisms are so much accustomed. This, however, is a fault on the right side, and one which will bear good fruits when rapid and brilliant execution is needed to develop the infinite variety of tone of this great instrument. All the internal metal pipes are made of an alloy of 5-9ths tin and 4-9ths lead. The front pipes are almost entirely of tin, there being 90 parts of that metal to only 10 of lead. The outer pipes are burnished and polished i n the same manner as those of the great continental organs ; the burnished metal, in fact, is made the chief ornament, and a most effective ово it is. ТЬл organ will be supplied with wind by means of steam power, as in the case of the Liverpool organ in St. George's Hall. Mr. ¿Form is making two eight-horse power engines for this тгогк, which will be able to work up to 50-horíe power with ease and give the very decided pressure of air required for playing with full power when all the stops are opened. The main reservoirs into which the compressed air is forced are placed in a caíate in a dry position. The feeders supplying the air are of a most ample size, and constructed ta receive their wind from the room above, and not from the locality in which they are placed. To carry out this arrangement, which is one of the highest importance, passages are provided for the windshafte to and from the organ to the chamber in which the main reservoirs are placed. The main reservoirs in turn deliver their wind to numerous subsidiary reservoirs in immediate connection with the pipes. The mechanical arrangements effected by the pressure of attenuated and compressed air vary from four to forty inches. The light touch of all the key-notes is alike. The pedal arrangements are divided into ten distinct parts. The external aspect or the. grand organ is very imposing. It is not duñ°ured by a case. The pipes, carefully graduated as to height, rise in four great clusters of spires, two at each end aud two in the centre. In the three sides which front the audience are three vaulted lofty openings which allow all the works to be seen, and in the background is a perfect forest of pipes. The base, or stand, of the organ is about 21ft. high. This is of carved oak with a recessed Italian doorway in the centre, in which, at the keys, the performer sits. The oak screen which forms the external face is, however, merely a screen, for the organ itself is built on massive stone foundations, which the oak work encloses. The instrument will cost, when completed, about £ 10,000. It has been built under the direct supervision of Sir Michael|Costa, assisted by Mr. Bowler, of the Crystal Palace, and Sir Michael pronounced it to be perfect in tone and working.

THE DETERMINATION OF THE PERCENTAGE OF SULPHUR IN IRONS.

ГР1НЕ analysis of irons is becoming increasingly -*- important, and the small quantities of impurities, which greatly alter their quality, renders accuracy indispensable, and adds to the difficulty of ensuring it. Although not sulphur, but phosphorus, is the greatest hindrance to the production of good iron, being generally present in a larger quantity, the former is nevertheless injurious. It may therefore be acceptable to those who are interested in the subject if I describe the method which has to my mind been the most satisfactory in the estimation of the quantity of sulphur in irons. I have analysed several specimens of pig iron according to the solution in nitrochloric acid method, with all due precautions, which, although exceedingly important, are often omitted in explanations of the process. The following oro results of the analyses :—

Sample 1st anal. 2nd anal. Dif.

No. I. percent, of S. 0 48 045 0-03

No. II. „ „062 069 007

No. III. „ „ 0-45 0-3 015

No. IV. „ „ 0 23 0-20 О 03

The precipitate with chloride of barium does not make its appearance until after warming tho bo for some time. After filtering and jng if well with boiling water it is saldora if ДЬн ¡-»líele to reader it white, which is objec_^БюЫе to a careful chemist. However, if the Tjaarptate is precipitated it all, I am convinced tits i it is entirely precipitated, and with euch résolu a» I hare giren above there is scarcely cause to complain much of the process.

Aa, however, puddle bare contain a very email quantity of sulphur, at leaet 10 grammes of iron in tine powder muet be employed in order to obtain a> wcighable and reliable quantity of sulphate of birioœ. Ноге acid must consequently be used, and it i* impossible to obtain a precipitate in the strongly acid solution, which, for well known reasons, must not be neutralised.

I will, therefore, briefly describe the method which I have employed to estimate sulphur in paddle bars and other irons containing small quantities of that element—a method which has given me highly satisfactory results.

A weighed quantity of iron is thrown into a capacious flask (about 2 pints capacity); »boat an onnce of water added, and the whole agitated to prevent caking in the after processes. A cork having two perforations is inserted into its mouth. Into one of these perforations passes о tube with bulb and funnel bent and containing a little mercury to allow of pouring intothe flask, bot to prevent back action. Into the other passes a tube bent at right-angles leading to a \J tubo, containing emetic pnts.«h free from sulphate. (Beyond this U tube I placed another containing hydrated oxide of lead in solution by caustio potash, which afcr repeated analyses was not in the slightest degree blackened.)

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Hydrochloric aeid м poured in at the funnel, and suction applied to draw it through the mercury into the flask,- sometimes water is added, and then acid, until there is a large excesss of acid. Wliea the actioD, after due addition of aeid, is very slow, the contents of the flask are boiled, then the flume taken away, and as soon as ebullition ha« ceased air is sucked through the apparatus. The boiling can after be advantageously rep'ited, and the suction again continued. The •till caustic solution in the U tube is emptied and rinsed out into a beaker. Pure chlorine gas is pissed through it; after boiling, sufficient hydrochloric acidia added to drive off the hypochlorous acid, and the boiling is continued until all or nearly all tin smell of this acid is gone. The sulphate is then precipitatod with chloride of barium.

The contents of the flask are filtered through asbestos, A small funnel with a rather ill-proportioned large neck is chosen. Enough asbestos bosWy to fit into the neck is taken and thrown iato the funnel, without any placing or pressing with the fingers. Oa pouring water in to fill the funnel, the pieces of asbestos swim about in the liquid, and gradually settle in the neck in such а «antier that the acid solution can be filtered quickly and perfectly clearly. After it has all gun« through, the flask need not be rinsed, out, or «he residue in funnel washed; but the latter shouldbs transferred with the asbestos to the flask, apun, and the funnel washed with a very small quantity of nitrochloric acid, which is allowed to trickle into the flask also. The black real due mixed with nitrobydrochlorie acid in very email quantity i»heated, covering the mouth of the ¿buk witA a glass plate. Some water and carbonate of" rodais added to take off the excess ef acid, and the liquid, after boiling, is filtered through paper, taking care that it is still slightly acid, and, of course, washed. Chloride of barium is added to this solution, and if, as is often the ease, a precipitate be produced, the whole is poored into the beaker with the former precipitate, and treated in the usual manner. By this method I obtained highly satisfactory results from irons which, according to the other process, would not show the least sign of precipitation when

chloride of barium was added in large excess, and the solution heated for some hours and then allowed to stand a whole day and heated again. It may be interesting to some to give a few of my results :—

ORDINARY PtTDDLE BARS.

Sample. 1st onal. 2nd anal. Dif.

No. I. per cent, of S. 0038 0 P26 0012 No. II. „ „ 0-073 0088 0016

No. III. „ „0 046 0-033 0 015

One could scarcely expect more satisfactory results than these are.

H. B. Hamilton, Analytical Chemist.

ON THE POLARISATION OF HEAT. *
Вт Professor Tyndall, F.R.S., &c.

IN the Philosophical Mngazine for November, 1835, the late Principal Forbes gave an account of tho experiments by which he demonstrated the polarisation of non-luminous heat. He first operated with tourmalines, and afterward*, by a happy inspiration, devised piles of mica plates, which from their gTeater power of transmission enabled him more readily and conclusively to establish the fact of polarisation. The subject was subsequently followed up by Melloni and other philosophers. With great sagacity Molloni turned to account hie own discovery, that the obscure rays of luminous sources were in part transmitted by black glass. Intercepting by a plate of this glass the light emitted by his oil lamp, and operating upon the transmitted heat, he obtained effects exceeding in magnitude any that could be obtained by means 6t the radiation from obscure sources. The possession of a more perfect ray-filter and a more powerful source of heat enables ns now to obtain, on a greatly augmented scale, the effects obtained by Forbes and Melloni.

Two large Nicol's prisms, such as those employed in my experiments ou tho polarisation of light by nebulous matter, were placed in front of an electric lamp, and so supported that cither of them could be turned round its horizontal axis. The beam from the lamp, rendered slightly convergent by tho camera-Ions, was sent through both prisms. But between them was placed a cell containing iodine dissolved in bisulphide of carbon in quantity sufficient to qnench the strongest solar light. Behind the prisms wasplaced a thermo-electric pile, furnished with two conical reflectors. The hinder face of the pile received heat from a platinum spiral through which passed an electric current regulaterl by a rheostat.

The apparatus was so arranged that, when the principal sections of the Nicole were crossed the needle of the galvanometer connected with thepile showed a deflection of 00° in favour of the posterior source of heat. One of the prisms was then turned so as to render the principal sections parallel. The needle immediately descended to zero, and passed on to 90° at the other side of it. Reversing, or continuing tho motion, so as to render the principal sections again perpendicular to each other, the calorific sheaf was intercepted, the needle doscended to zero and went up to its first position.

So copious, indeed, is the ow of polarised heat that a prompt rotation of the Nicol would oanse the needle to spin several times round over its graduated dial.

These experiments were made with the delical galvanometer employed in my researches up »a radiant beat. But tho action is so strong as to cause a coarse kcturc-ro >m galvanometer, with needles Cin. long and paper indexes a square inch each in area, to move through an arc of nearly 180«.

Reflection, refraction, dispersion, polarisation (plane and circular), double refraction, the formation of invisible images both by mirrors and lenses, may all be strikingly illustrated by the employment of the iodine filter and the electric light.

Take, for example, the following experiments: —The Nicole being crossed, tho needle of the galvanometer pointed to 78« in favour of the heated platinum spiral behind the pile. A plato of mica was then placed across the dark beam with its principal section inclined at an angle of 46« to those of the Nicole. The necdlo instantly fell to zero, and went up to 90« on the other sido.

* From the Philosophical Magazine.

And, for circular polarisation :—The Nicole being orossed and the needle pointing to 80« io favour of the platinum spiral, a plate of rock crystal cut perpendicular to the axis was placed across the dark beam. The needle fell to zero, and went to 90« on the other eide.

The penetrative power of the heal here employed may be inferred from tbe fact that it traversed about 12in. of Iceland spar, and about ljin. of the cell containiog the solution of iodine.

ON THE PHENOMENA OF COM-
BUSTION.

SPECIAL REPORT.

THE last of the present series of Cantor Lectures on this subject was delivered by Dr. Benjamin Paul, F.C.S., on Monday, 28th ult., in the presence of a largo audience. The lecture had specially to do with tho use of combustible materials for producing li^ht, with the varieties of illuminating materials—coal gas, petroleum, and paraffin oil, and also with the measurement of iight. At the outset, the lectnrer observed that the evolution of light wae another of the effects of combustion which was of practical utility. It was chiefly by means of combustion that artificial light was produced. One important fact we had to consider in regard to combustion as a source of light was that all material substances became luminous when they were sufficiently heated, and this was a special characteristic of solid substances, which, howover, were not changed in their comlition or natura by suoh heating. Having shown tho luminosity of solid substances by experiment, Dr. Paul adverted to the fact that liquids also became luminous when heated, under conditions, however, when they were not converted into vapour. Melted metals and glass, for instance, emitted light at high temperatures ; gases and vapours were least of all capable of luminosity whon heated. At a temperature of 1000 degrees, liquid substances emitted a reddish light, and this degree of heat was termed *' red heat," which »gain, in proportion to tbe temperature, was. distinguished by the names " red,"' or " dell" beat ; oragain bythose of "cherryred " or " brick red." At very high temperatures, solid and liquid substances gave a colourless light, termed "whitle heat." To produce artificial light, we must first obtain a very high température in some substance capable of becoming luminous in that condition. If hydrogen gas were burned with oxygen, a very intense degree of heat would be attained, but the water vapour which was the product in this gas had such a degree of continuity that it gave a gas affording barely sufficient light to be visible. After explaining the production of lime-light, and showing some experiments with magnesia, the lecturer adverted to carbon. Carbonaceous substances were easy to illuminate. Tho chief characteristic of very inflammable substances was the presence of carbon, which in some cases was as much as 80 per cent. Oil, tallow, and the various materials nsed in lamps were susceptible of vaporisation, and that, too, without giving any fixed carbonaceous residue, which was not the case with coal, wood, resin, or such materials. Dr. Paul next asked attention to the form of flame, which, he said, was partly determined by the war in which the combustible gas was supplied, and partly by the reaction of the heated prctdnct of combustion and the atmosphere upon each other. The shape of the luminous flame might he different from that of a candle, but in every caee there wae the same relative disposition of tbe zones in which the progressive changes took place. The production of flame from any substance corresponded to the amount of carbon i« contained, and to this was owing the difference between the flame from a candle and that from coal gas. After some remarks on tho comparative merits of olefiant, marsh, and benzole gase», the lecturer alluded to paraffin oil, and said that, whereas marsh gas contained 73 per cent of carbon, paraffin oil contained 85, and the former contained half as much carbon as olefiant gas. The vapour of marsh gas contained one-seventeenth as ranch carbon in a given volume as tbe vapour of paraffin, which was very much more dense. The samo was the case with benzole gas, which contained four times as much carbon as an equal volume of marsh gas. Tho latter gas burnt with a pale flame, leaving no sooty deposit or luminous effect, and the formor burnt with an iutensely. luminous flame, and over and above that left, a largo deposit of carbon, which, unless regulated, reudered tue ll-.iiie sooty and smoky. In all illuminating materials it was necessary to regulate the conditions in such a way that we might get a deposit of carbon to such an extent as would make a flame in the highest degree luminous, without overstepping the line at which it became smoky. The lecturer next referred to the heat of rooms, and observed that most people seemed to forget that in proportion to the quantity of artificial heat introduced into a room in that proportion was the air deteriorated, defiant gas produced the greatest effect upon the atmosphere, by destroying the largest amount of air; marsh gas next; carbonic acid gas next, and hydrogen gas least of all, because it was the most volatile. Dr. Paul then referred to the oomplaints so rife relative to the bad quality of the gas now supplied, and said that although these complaints might to some extent be based on just grounds, yet he thought much of the fault lay with the burners in use. He here exhibited some of Mr. Sugg's improved burners, and coneluded by regrettiug that the time at his disposal bad prevented him from entering into tho interesting subject of paraffin oil.

We understand that the next series of Cantor Lectures will be given by Dr. Williams, on "Fermentation," and that they will take place on the last two Mondaye in April, and the first two Mondays in May.

STRUCTURE OF THE LIVER.

AN important paper on this subject by Professor Hering, of Vienna, appears in the j ust published third part of Strieker's Handbuch ven den Gen-eben. This gland is the most intricate in the body of the higher animals, and its functions present a corresponding complexity; on these grounds it has been subjected to very careful microscopical examination, as well as experimental investigation, by many of the best observers, both here and abroad, amongst whom Professor Hering holds a distinguished place. Speaking broadly, the liver consists of an immense number of pear-shaped bodies or lobuli, separated from one another by a delicate investment of connective tissue. Between these spread branches of the portal vein, conveying blood to the liver from the intestines, and of the hepatic artery, the ultimate branches of the latter discharging themselves into those of the former. The capillary vessels thus formed penetrate the substance of each lobule and reunite in a central vessel, which, issuing from the extremity of the lobule like the stalk of a pear, coalesces with others to form the hepatic veins which convey the blood that has circulated through the organ to the heart. The substance of the lobuli themselves is composed of cells, the office of which is in part to secrete bile, and in part to produce tho substance termed glycogen. The writer observes that the capillary system of the portal vein, as a general rule, exhibits large capillaries and a narrow-meshed plexus, whilst that of the hepatic vein exhibits small capillaries and a plexus with wide meshes. The foregoing facts are now fairly established, but the poiuts to which Professor llering's attention has been particularly directed are connected with the distribution of the biliary duets. These, he states, consist of a close network of delicate canals running between tho hepalio cells, with meshes equalling the cells in diameter, or, in other words, the canals run between the flat surfaces of two adjoining Cells. The capillaries, on the other hand, occupy the angles formed by the junction of three or more cells. This description particularly applies to the rabbit. In man and the dog, biliary canals are also found at the angles of the cells. For the sake of clearness, we have mado use of ^he term biliary canals, but Professor Hering observes that they have no proper wall so long as they are contained within the lobuli. These walls are, in fact, the cells themselves, and they may fairly be represented by the tubes that would be produced by grooving two solid bodies, and applying the corresponding channels to one another. He has not been able, in any instance, in the rabbit at least, to discover a blind extremity of a biliary tube. He describes the hepatio cells as presenting various forms, according to the direction in which they happen to be divided in the section, being sometimes quadrangular, sometimes polygonal, and presenting the grooves above mentioned for the passage of the capillaries, and for tho formation of the ducts. They contain one,

or occasionally two, nuclei of spherical or elliptic shape, together with some granules of biliary pigment and fat molecules. He finds the liver to be richly supplied with lymphatics, which, as in other organs, chiefly accompany the connective tissue. The system presents this peculiarity, however, that both the capillaries and the larger vessels freely anastomose with each other. Though he has carefully examinedt ho point, he has been unable to follow the nerves of tho liver into the cells, a relation which has been maintained to exist by Pflüger. (Academy, No. II., p. 47.) Professor Hering states distinctly that all demonstrable nerve trunks lie outside the lobuli.

PLATINISED LOOKING-GLASSES.*
By С Widemajtn.

NO. III.

(Continued from page 27.)

IT is now unnecessary to use glass free from colour or to require parallelisms of the two surfaces. Bubbles of air, stripes, foreign bodies, pieces of the pots, 4c, Sec, do not interfere with the process. There is then an economy of 50 per cent, in the glass.

In order to manufacture a looking-glass of 5 millimetres thickness, they use at the St. Gobaia works a plate measuring 10 millimetres thickness.

At the Wailly-sur-Aisuo works, plates are used having but 7'5 millimetres thickness, as it is only necessary to polish the glass on one side. From this a saving is mad« of 25 per cent on the thickness of the glass.

Very correct calculations show that Mr. Dodé secures an economy of SO per cent, on platinised glasses, as he uses for that purpose only inferior glass commonly used for flagons; even common brittle glass can be used without the least difficulty. To this saving there is another to be added, which will astonish the reader. A square metre of glass absorbs ahont 183 grammes of mercury and 550 grammes of tin, representing about a cost of 4 francs, 40 centimes. A square yard of platinised glass costs 1 fra no and 20 centimes for platina. It results from this, that at the Wailly-sur-Aisne works, tho superficial square yard of platinised gloss is sold at an average of 25 francs. This price is doubled in the mercury manufacture.

There is another circumstance for which this new process is recommended to the public. It is with great difficulty that mirrors are obtained with a curved surface. By the platina process this difficulty disappears, and it is as easy to manufacture curved, round, etc., as horizontal mirrors. There is also no inconvenience arising from upsetting the glosses in transportation or in placing them in the frame.

Already in this country a company has been organised to manufacture reflectors by the means of silver mica leaves on the posterior face, and fastened together so as to obtain a large reflective surface possessing the desired curves. They are cheap, and easily repoired; but they meet with two great difficulties: the quick alteration of the silvery surface caused by the hydrosulphurous gases of coal with which locomotive reflectors are always in contact, and the want of transparency of the mica and its yellow colour. I have no doubt that by the adoption of the platina these evils would have found their remedy, for, as it has been seen before, the reflecting surface is on the anterior part of the glass.

A quite peculiar property of the platinised mirrors will no doubt be applied by architects. The platinised glasses forming mirrors are transparent when the light passes through them. A person placed in the rear of an office can see everything going on in the front office without himself being seen. I insist particularly on this property; it appears to me to give to the platinised glass quite a new application, which will increase its sale. This transparency is easily explained considering the small quantity of platina deposited on the glass, which quantity is not large enough to give opacity to the glass and prevent the luminous rays from passing through it. This transparency has received a very amusing application quite lately in Paris. Mirrors called mirrors a surprise, are sold, which, when a black paper at the back of the glass is removed, allows a photograph or any other image to be seen through the metallised surface appearing a<

a spectre; this photograph is simply applied at the posterior side of the reflecting part, and oiled in order to add to its transparency. This toy is varied in тегу different ways, and has just been applied in the new play of "The White Cat," at Paris, and has caused an immense sensation. So I have no doubt that the inventive mind of the Americans will find thousands of application« for this property, either in applying it te the decoration of stores, or to external ornamentation. In theatres or concert halls among flowers it produces the most fairy-like effect. Tho window glosses of n parlour made thus would transparent in daytime, and at night when the shutters are closed the whole window woad appear as a large looking-glass, and reflect all lights and objects in the apartment.

The manufacture of glasses with amalgam necessitates great labour. In order to obtain 50 metres of looking-glass a large number of hands and a largo plot of ground are required. These glasses must remain loaded with weights from 15 to 20 days; then 20 days more are required to eliminate the superabundance of mercury, and three months more are required before they are saleable; not to mention all the precautions that have to he taken at every moment in the snipping and setting in frame. MM. Dode and Faure are able to platinise a surface of 800 metres a day, with ouly the aid of a few hands, as one workman is able to platinise 50 metres of glass, in 12 hours' work.

• From the Scientific American.

EXHAUST STEAM FOR HEATING PURPOSES.

Br Chaules E. Emery.

QUESTIONS are frequently asked regarding the relative economy of heating buildings with live steam taken direct from the boiler, or with the exhaust steam from a non-condensing engine.

Though the steam engine is a heat engine, the best examples utilise only ten per cent, of the heat in the steam used, consequently at least 90 per cent, of the heat which enters the cylinder escapes with the exbaustiog steam, and can be made available in no way except for heating purposes.

The temperature of the exhaust stetm from a condensing engine is from 130* to 140"? Fahr., and that from a лол-eondensing engine is from 212e to 220a and upward, varying aacording to the amount of back pressure in either ease. A portion of the escaping heat is generally utilised in heating the feed-water for the boiler. la the condensing engine the low temperature of the exhanst steam, and the liability to'.air leakages and loss of vacuum in long pipes, makes it impracticable to save any more of the heat than that mentioned, and the remainder is necessarily wasted in heating the condensing water. In the non-condensing engine there is on the average ten per cent, of the heat utilised by the nee of a feed-water heater, in addition to the ten per cent, transmuted into work, consequently eighty per cent, of the original amount of heat remains in the exhaust steam, and is usually wasted in the atmosphere. If this large quantity could be used for heating buildings without interfering with the performance of the engine, there would be no doubt of tho value of the system—the heat in fact would cost nothing; but it is evident that in order to cause this steam to traverse throngh heating-pipes and coils it must have sufficient pressure in excess of that of the atmosphere to enable it. to overcome the increased resistance. The additional pressure varies from two to rive pounds and upwards per square inch, and acts as во much back pressure upon the piston, thereby reducing the power of the engine. The power lost must be supplied by increasing the mean pressure upon the driving side of the piston, and the question becomes :—What is the relative cost in fuel of supplying the heatingpipes with steam direct from the boiler, as compared with that required for the extra power necessary to circulate the exhaust steam through the building 1

The answer to this problem depends upon the particular circumstances of each case, and to make the subject generally understood, it is first necessary to investigate some of the known facts in regard to low-presiure steam-beating apparatus.

Manufactories whore steam-power is employed

f»oer*lIy hare » Urge number of windows for ib* convenience of the workmen, and are often sore or leas exposed to cold draught« from hoistways, staircases, and outer doors, and though the temperature need not be so high as in dwellingbouses, it would be unsafe to allow less than one square foot of heating surface in the heating pipes and coils to every 100 cubic feet of space to be heated. In order to form a safe estimate of the amount of fuel required when the steam is taken direct from the boiler, we may assume as an extreme case that the difference between the externa] air and that of the room is to be 69''; then, according to the experiments and formula of Tredgold, we find that it will require three «ad one-eighth square feet of surface to eondense a pound of steam per hour, and if one pound of coal evaporate eight pounds of water, it will aupply steam to (8 X 3125 =1) 25 square feet of heating surface end will heat (25 x 100]=) •2500 cubic feet of space for one hour. This estimate will be correct for average circumstances, ont will not spply to all cases of low-pressure steam-heating, especially where the rooms are unusually exposed either to draughts of air, or jjreat extremes of temperature.

In estimating the greatest amount of space that can be heated by the exhaust steam of an engine, it should be borne in mind that the quantity of steam discharged necessarily varies •with the work being done, and as the temperature of the building requires to be constant, we can only utilise the quantity of heat escaping when the .'engine is lightly leaded. For instance, an -engine of SO-horse power may be loaded occasionally to only 40-horse power for half an hoar or more at a time. If each horse power require o n the average 31b. of coal per hour, 40-horse power will require 1201b. As has been before mentioned, the exhaust steam from an engine contains S-lOtbs of the heat received from the fuel, so in the present ease the maximum heating effect is equal to 8-10th of 1201b., or 961b. of coal per hoar ; and as each pound of coal will beat ¿500 cubic feet of space, 951b. will beat 240,000 cubic feet, equal to Jthe capacity of a building 100ft. long, 60ft. wide, and 40tt. high. The extra power required to overcome the back pressure in that sized engine could not well exceed 10-horse power, which would cost 301b. of coal per hour; and as 961b. would be required were steam taken direct from tbe boiler, the saving is (96 — 30 =) 667b. per honr, or 6S per cent. If the quantity of -space heated be less than that mentioned, the percentage of saving will be less; for instance, to heat 150,000ft. of space in the ordinary way would require 601b. of coal per honr ; but with the exhaust steam in the above instance the cost will still be 301b., so the saving will be 50 per eeet. In warm days in winter, when less heat is required in the buildings, the same power will be taken from the engine to supply the less quantity of heat, so that the percentage of saving will be less. There would be some saving, however, whenever it required more than 301b. of coal to heat the rooms. In case each horse power required more coal per hour than that stated, the advantages of exhaust heating would be correspondingly diminished, unless the size of the engine and amount of power necessary to distribute the steam were also less. Iu some instance», probably, the system is productive of loss as compared with the nee of live steam, so the true plan is to make accurate calculations in each case. The following directions may therefore assist many readers—

To ascertain whether beating by exhaust stoam is economical where it has already been applied, the first step is to measure the extra back présame on the piston, which can be done by indicating the engine when ths steam is escaping freely into the atmosphere, and when the «xhaust is throttled for beating purposes, •nd comparing the back pressures shown bv the diagrams. If this be not convenient, one leg of an inverted glass siphon containing mercury may be connected to some enlargement ot the exhaust-pipe, and the mean difference in level noted in the two cases the same as before. One pressure corresponds to about 2 (2037) inches of mercury. A longer syphon filled with water may be used with some inconveniences. In such case, one pound pressure corresponds to «column of water 2'3 feet high and CO" temperature, or 2-4 feet high at temperature of 205°.

Having ascertained the extra back pressure, the horse-power required to overcome it may be ascertained by the following rule, viz.: Multiply t egetber the back pressure, the area of the piston

in square inches, and the speed of piston in feet
per minute, and divide the product by-33,000.*

The next step is to ascertain the coal required
per horse-power per hour. This should be done,
when practicable, by regular experiment. In
other cases, it may be assumed that engines
working with a steam pressure of 501b. and
under, with little expansion, will require 5 to
61b. of coal per horse-power per hour. With
more expansion, 4 to 51b. will be required ; and
tbe most improved form of expansive engines,
working with steam at 801b. pressure, wilt
furnish a horse-power for 31b. of ooal per hour.
By multiplying the horse-power due to the in-
creased back pressure by the coal required per
horse-power per hour, and the product by 2500,
the result will be the leset number of cubic feet
of space which can be heated economically by the
exhaust steam from that engine. The advantages
nnder different circumstances may be ascertained
in the manner previously stated.

In heating a building by exhaust steam, particular attention should be given to the size and arrangement of the pipes. A main exhaust pipe should be run up through tbe building and out of the roof in the usual manner. This pipe should be larger than is ordinarily employed, so as to form a kind of expansion chamber to equalise the exhaust pressure. From the vertical exhaust pipe the heating pipes may be led out for each floor of tbe building. A common plan is to put a good-sized cast-iron pipe under the workbenches along the sides of the rooms. Such pipes should be connected by bolted Sanges, and ample provision made for expansion and contraction. Heating coils of the ordinary construction may also be used, care being taken to make the leading pipes with as few bends as possible and of sufficient size. To obtain the proper size of pipe for a given case, the following formula may be used, which is founded on some experiments made by the writer for the United States Government, viz. : a = W ~ 46 (p + 3) in which a = area of steam-pipe in square inches, W the weight of steam in pounds delivered per hour, and p the difference in pressure. Assuming as an extreme that 24 square feet of surface (.<) will condense one pound of exhaust steam per hour, then, when the difference in pressure equals one pound, a ■=. t -H 440. The following is then a safe rule :— Divide the heating surface in square feet by 400, the result is the proper area of the pipe in square inches. The following table gives the amount of surface which will be supplied with steam through pipes of the sizes mentioned :—

Amount of Surface.

Diameter of Pipe.

) inch

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40 square feet
75

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REVIEWS.

-—♦—

Continental Farming and Peasantry. By Jas.
Howard, M.P. London: W. Bidgwey, 169 ,
Piccadilly.

THE comparison of results obtained from two opposite systems must always decide the question. Mr. Howard's book in this manner contributes to settle the question of large or small farming. Travelling himself through the farming districts of France and Belgium, where small holdings prevail, he »hows not only that the produce does not equal that of English farming, but that the holders are worse off; do more work for less money with less results than English farm labourers, although possessed of the advantages of a more favourable climate. Mr. Howard would permit small holdings on large estates as rewards held out by the owner (as in the case of Lord Lichfield) to deserving and thrifty workmen in later life. He would not, however, encourage the sub-division of holdings into smaller lots. One fact which he calls attention to is worth notice, namely, that in Belgium, where the small farm system is said to obtain such favour, the Trades' Union Congress, which met some time baok at Brussels, condemned the system of "petite culture,'' and resolved that when communism in land was gained it would be necessary to farm on a large scale in order to take advantage of machinery, &c, in the production of food.

Ecery Man Bis Oitn Lawyer. By A Barrister.

London : Lockwood and Co., Stationers'-hall

court, E.G. Ths eighth edition of this useful book needs little more from us than mention. For 6s. 8d. our readers can obtain a trusty adviser in every point of law, whose first charge is his only one, and who will not advise with a view to litigation and long bills, as lawyers in the flesh too often do.

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§0 ) The following nereis« will test the
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The pipes should be slightly inclined, so that the condensed water will move in the same direction as the steam. Tho ends of the various heating pipes and coils should be connected with a water-pipe terminating near the boiler in an inverted sipbon, the shorter leg of which should be about seven feet long. The bend may extend under ground if necessary. This siphon should deliver the condensed water into a tank where it can be returned to the boiler. An air-cock should be placed iu the water-pipe to allow the air to escape in starting.

Arrangements should be made so that tho exhaust steam can be shut off from each room separately by a valve, and in some instances it may be desirable to admit live steam into portions of the pipes when the engine is net iu motion.—American Artisan.

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THE LUMINOSITY OF PHOSrHORUS.-Пегт W. Mullcr, of Perleberg, gives an explanation ot the well-known luminosity exhibited by phosphorus in the dark. It depends on slow combustion or combination with oxygen, but does not toko place iu pure oxygen, except when It la diluted by other gases, as is the case In the atmosphere. In other utmospheres, as hydrogen or nitrogen, tho phenomenon does not occur.

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'Many engineers will find the following formula more convenient :—

cPtrp H.P. =

2*2,000
which, put In the form of a rule. Is: Horse-power
equals the square of the diameter {</; iu Inches, multi-
plied by tbe length of a aiugle stroke (s) in inches,
multiplied by the number »i revolutions per minute
(r), multiplied by the extra back pressure (p), and
divided by 242,00*. wn

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