Chapter V: Introduction (2)

1st. The real nature of centrifugal force. That in the dynamical sense of the term force, this is not a force at all: that it is not capable of producing motion, that the force which is really exerted on a revolving body is the centripetal force, and what we are taught to call centrifugal force is nothing but the resistance which a revolving body opposes to this force, precisely like any other resistance.

2d. The direction of the deflection, to which the centrifugal force is the resistance, which is straight to the center.

3d. The measure of this deflection; the versed sine of the angle.

4th. The reason of the laws of centrifugal force; that these laws merely express the relative amount of the deflection, and so the amount of the force required to produce the deflection, and of the resistance of the revolving body to it, in all different cases.

5th. That the deflection of a revolving body presents a case analogous to that of uniformly accelerated motion, under the action of a constant force, similar to that which is presented by falling bodies;[1] and finally,

6th. How to find the coefficient, by which the amount of centrifugal force exerted in any case may be computed.

[Footnote 1: A body revolving with a uniform velocity in a horizontal plane would present the only case of uniformly accelerated motion that is possible to be realized under actual conditions.]

I now pass to some other features.

_First_.--You will observe that, relatively to the center, a revolving body, at any point in its revolution, is at rest. That is, it has no motion, either from or toward the center, except that which is produced by the action of the centripetal force. It has, therefore, this identity also with a falling body, that it starts from a state of rest. This brings us to a far more comprehensive definition of centrifugal force. This is the resistance which a body opposes to being put in motion, at any velocity acquired in any time, from a state of rest. Thus centrifugal force reveals to us the measure of the inertia of matter. This inertia may be demonstrated and exhibited by means of apparatus constructed on this principle quite as accurately as it can be in any other way.

_Second_.--You will also observe the fact, that motion must be imparted to a body gradually. As distance, _through_ which force can act, is necessary to the impartation of velocity, so also time, _during_ which force can act, is necessary to the same result. We do not know how motion from a state of rest begins, any more than we know how a polygon becomes a circle. But we do know that infinite force cannot impart absolutely instantaneous motion to even the smallest body, or to a body capable of opposing the least resistance. Time being an essential element or factor in the impartation of velocity, if this factor be omitted, the least resistance becomes infinite.

We have a practical illustration of this truth in the explosion of nitro-glycerine. If a small portion of this compound be exploded on the surface of a granite bowlder, in the open air, the bowlder will be rent into fragments. The explanation of this phenomenon common among the laborers who are the most numerous witnesses of it, which you have doubtless often heard, and which is accepted by ignorant minds without further thought, is that the action of nitro-glycerine is downward. We know that such an idea is absurd.

The explosive force must be exerted in all directions equally. The real explanation is, that the explosive action of nitro-glycerine is so nearly instantaneous, that the resistance of the atmosphere is very nearly equal to that of the rock; at any rate, is sufficient to cause the rock to be broken up. The rock yields to the force very nearly as readily as the atmosphere does.

_Third_. An interesting solution is presented here of what is to many an astronomical puzzle. When I was younger than I am now, I was greatly troubled to understand how it could be that if the moon was always falling to the earth, as the astronomers assured us it was, it should never reach it, nor have its falling velocity accelerated. In popular treatises on astronomy, such for example as that of Professor Newcomb, this is explained by a diagram in which the tangential line is carried out as in Fig. 1, and by showing that in falling from the point A to the earth as a center, through distances increasing as the square of the time, the moon, having the tangential velocity that it has, could never get nearer to the earth than the circle in which it revolves around it. This is all very true, and very unsatisfactory. We know that this long tangential line has nothing to do with the motion of the moon, and while we are compelled to assent to the demonstration, we want something better. To my mind the better and more satisfactory explanation is found in the fact that the moon is forever commencing to fall, and is continually beginning to fall in a new direction. A revolving body, as we have seen, never gets past that point, which is entirely beyond our sight and our comprehension, of beginning to fall, before the direction of its fall is changed. So, under the attraction of the earth, the moon is forever leaving a new tangential direction of motion at the same rate, without acceleration.

(_To be continued_.)

* * * * *

COMPRESSED AIR POWER SCHEMES.

By J. STURGEON, Engineer of the Birmingham Compressed Air Power Company.

In the article on "Gas, Air, and Water Power" in the _Journal_ for Dec. 8 last, you state that you await with some curiosity my reply to certain points in reference to the compressed air power schemes alluded to in that article. I now, therefore, take the liberty of submitting to you the arguments on my side of the question (which are substantially the same as those I am submitting to Mr. Hewson, the Borough Engineer of Leeds). The details and estimates for the Leeds scheme are not yet in a forward enough state to enable me to give them at present; but the whole case is sufficiently worked out for Birmingham to enable a fair deduction to be made therefrom as regards the utility of the system in other towns. In Birmingham, progress has been delayed owing to difficulties in procuring a site for the works, and other matters of detail. We have, however, recently succeeded in obtaining a suitable place, and making arrangements for railway siding, water supply, etc.; and we hope to be in a position to start early in the present year.

I inclose (1) a tabulated summary of the estimates for Birmingham divided into stages of 3,000 gross indicated horse power at a time; (2) a statement showing the cost to consumers in terms of indicated horse power and in different modes, more or less economical, of applying the air power in the consumers' engines; (3) a tracing showing the method of laying the mains; (4) a tracing showing the method of collecting the meter records at the central station, by means of electric apparatus, and ascertaining the exact amount of leakage. A short description of the two latter would be as well.

TABLE I.--_Showing the Progressive Development of the Compressed Air System in stages of 3000 Indicated Horse Power (gross) at a Time, and the Profits at each Stage_

_____________________________________________________________________________

Gross | 3000 | 6000 | 9000 | 12,000 | 15,000 | Indicated | Ind. | Ind. | Ind. | Ind. | Ind. | Horse Power | H.P. | H.P. | H.P. | H.P. | H.P. | at Central | | | | | | Works: | | | | | | -----------------------------------------------------------------------------

Thousands of | 1,080,000 | 2,160,000 |3,240,000 | 4,320,000 |5,400,000 | Cubic Feet at 45 | | | | | | lbs. pressure | | | | | | at engines | | | | | | Deduction for | 17,928 | 70,927 | 154,429 | 267,529 | 409,346 | friction and | | | | | | leakage | | | | | | Estimated net | 1,062,072 | 2,089,073 |3,085,571 | 4,052,471 |4,990,654 | delivery | | | | | | -----------------------------------------------------------------------------

CAPITAL | | | | | | EXPENDITURE-- | | | | | | Purchase and pre-| £12,500 | (amounts below apply to extension of works) | paration of land | | | | | | Machinery | 27,854 | £25,595 | £25,595 | £25,595 | £25,595 | Mains | 10,328 | 10.328 | 10,328 | 10,328 | 10,328 | Buildings | 8,505 | 4,516 | 4,632 | 4,614 | 4,594 | Parlimentary and | | | | | | general expenses,| 20,000 | .. | .. | .. | .. | royalty, &c. | | | | | | Engineering | 3,268 | 1,820 | 1,825 | 1,824 | 8,823 | Previous Capit-| | 82,455 | 124,714 | 167,094 | 209,455 | al Expenditure | .. | | | | | Total Cap. Exp. | £82,455 | £124,714 | £167,094 | £209,455 | £251,795 | -----------------------------------------------------------------------------

ANNUAL CHARGES-- | | | | | | Salaries, wages, | | | | | | & general working| £6,405 | £7,855 | £9,305 | £10,955 | £12,480 | expenses | | | | | | Repairs, renewals| 2,780 | 5,198 | 7,622 | 10,045 | 12,467 | &c.(reserve fund)| | | | | | Coal, water, &c. | 1,950 | 3,900 | 5,850 | 7,800 | 9,750 | Rates | 370 | 674 | 980 | 1,285 | 1,585 | Contingencies of | | | | | | horse power = 5 | 575 | 881 | 1,187 | 1,504 | 1,814 | per cent on above| | | | | | Total Ann. Exp. | £12,080 | £18,508 | £24,944 | £31,589 | £38,096 | -----------------------------------------------------------------------------

Revenue at 5d. | | | | | | per 1000 cub. ft.| 22,126 | 43,522 | 64,282 | 84,426 | 103,971 | (average) | | | | | | Profit |12.18 p.ct.|20.06 p.ct.|23.54 p.ct.|25.22 p.ct.|26.16 p.ct.| |= 10,046 | = 25,014 | = 39,338 | = 52,837 | = 65,875 | -----------------------------------------------------------------------------

TABLE II.--_Cost of Air Power in Terms of Indicated Horse Power_.

Abbreviated column headings:

Qty. Air: Quantity of Air at 45 lbs. Pressure required per Ind. H.P. per Hour.

Cost/Hr.: Cost per Hour at 5d. per 1000 Cubic Feet.

Cost/Hr. w/rebate: Cost per Hour with Rebate when Profits reach 26 per Cent.

Cost/Yr.: Cost per Annum (2700 Hours) at 5d. per 1000 Cubic Feet.

Cost/Yr. w/rebate: Cost per Annum with Rebate when Profits reach 26 per Cent.

Abbreviated row headings:

CASE 1.--Where air at 45 lbs. pressure is re-heated to 320° Fahr., and expanded to atmospheric pressure.

CASE 2.--Where air at 45 lbs. pressure is heated by boiling water to 212° Fahr., and expanded to atmospheric pressure.

CASE 3.--Where air is used expansively without re-heating, whereby intensely cold air is exhausted, and may be used for ice making, &c.

CASE 4.--Where air is heated to 212° Fahr., and the terminal pressure is 11.3 lbs. above that of the atmosphere

CASE 5.--Where the air is used without heating, and cut off at one-third of the stroke, as in ordinary slide-valve engines

CASE 6.--Where the air is used without re-heating and without expansion.

_____________________________________________________________________
| Qty. Air | Cost/Hr. | Cost/Hr. | Cost/Yr. | Cost/Yr. |
| | | w/rebate | | w/rebate |
| Cub. Ft. | d. | d. | £ s. d. | £ s. d.|
---------------------------------------------------------------------
CASE 1 | 125.4 | 0.627 | 0.596 | 7 1 1 | 6 14 0½|
CASE 2 | 140.4 | 0.702 | 0.667 | 7 17 11 | 7 10 0 |
CASE 3 | 178.2 | 0.891 | 0.847 | 10 0 5½ | 9 10 5½|
CASE 4 | 170.2 | 0.851 | 0.809 | 9 11 5½ | 9 1 10½|
CASE 5 | 258.0 | 1.290 | 1.226 | 14 10 3 | 13 15 9 |
CASE 6 | 331.8 | 1.659 | 1.576 | 18 13 3 | 17 14 7 |
_____________________________________________________________________

The great thing to guard against is leakage. If the pipes were simply buried in the ground, it would be almost impossible to trace leakage, or even to know of its existence. The income of the company might be wasting away, and the loss never suspected until the quarterly returns from the meters were obtained from the inspectors. Only then would it be discovered that there must be a great leak (or it might be several leaks) somewhere. But how would it be possible to trace them among 20 or 30 miles of buried pipes? We cannot break up the public streets. The very existence of the concern depends upon (1) the _daily_ checking of the meter returns, and comparison with the output from the air compressors, so as to ascertain the amount of leakage; (2) facility for tracing the locality of a leak; and (3) easy access to the mains with the minimum of disturbance to the streets. It will be readily understood, from the drawings, how this is effected. First, the pipes are laid in concrete troughs, near the surface of the road, with removable concrete covers strong enough to stand any overhead traffic. At intervals there are junctions for service connections, with street boxes and covers serving as inspection chambers. These chambers are also provided over the ball-valves, which serve as stop-valves in case of necessity, and are so arranged that in case of a serious breach in the portion of main between any two of them, the rush of air to the breach will blow them up to the corresponding seats and block off the broken portion of main. The air space around the pipe in the concrete trough will convey for a long distance the whistling noise of a leak; and the inspectors, by listening at the inspection openings, will thus be enabled to rapidly trace their way almost to the exact spot where there is an escape. They have then only to remove the top surface of road metal and the concrete cover in order to expose the pipe and get at the breach. Leaks would mostly be found at joints; and, by measuring from the nearest street opening, the inspectors would know where to break open the road to arrive at the probable locality of the leak. A very slight leak can be heard a long way off by its peculiar whistling sound.

The next point is to obtain a daily report of the condition of the mains and the amount of leakage. It would be impracticable to employ an army of meter inspectors to take the records daily from all the meters in the district. We therefore adopt the method of electric signaling shown in the second drawing. In the engineer's office, at the central station, is fixed the dial shown in Fig. 1. Each consumer's meter is fitted with the contact-making apparatus shown in Pig. 4, and in an enlarged form in Figs. 5 and 6, by which a current is sent round the electro-magnet, D (Fig. 1), attracting the armature, and drawing the disk forward sufficiently for the roller at I to pass over the center of one of the pins, and so drop in between that and the next pin, thus completing the motion, and holding the disk steadily opposite the figure. This action takes place on any meter completing a unit of measurement of (say) 1,000 cubic feet, at which point the contact makers touch. But suppose one meter should be moving very slowly, and so retaining contact for some time, while other meters were working rapidly; the armature at D would then be held up to the magnet by the prolonged contact maintained by the slow moving meter, and so prevent the quick working meters from actuating it; and they would therefore pass the contact points without recording. A meter might also stop dead at the point of contact on shutting off the air, and so hold up the armature; thus preventing others from acting. To obviate this, we apply the disengaging apparatus shown at L (Fig. 4). The contact maker works on the center, m, having an armature on its opposite end. On contact being made, at the same time that the magnet, D, is operated, the one at L is also operated, attracting the armature, and throwing over the end of the contact maker, l¹, on to the non-conducting side of the pin on the disk. Thus the whole movement is rendered practically instantaneous, and the magnet at D is set at liberty for the next operation. A resistance can be interposed at L, if necessary, to regulate the period of the operation. The whole of the meters work the common dial shown in Fig. 1, on which the gross results only are recorded; and this is all we want to know in this way. The action is so rapid, owing to the use of the magnetic disengaging gear, that the chances of two or more meters making contact at the same moment are rendered extremely small. Should such a thing happen, it would not matter, as it is only approximate results that we require in this case; and the error, if any, would add to the apparent amount of leakage, and so be on the right side. Of course, the record of each consumer's meter would be taken by the inspector at the end of every quarter, in order to make out the bill; and the totals thus obtained would be checked by the gross results indicated by the main dial. In this way, by a comparison of these results, a coefficient would soon be arrived at, by which the daily recorded results could be corrected to an extremely accurate measurement. At the end of the working day, the engineer has merely to take down from the dial in his office the total record of air measured to the consumers, also the output of air from the compressors, which he ascertains by means of a continuous counter on the engines, and the difference between the two will represent the loss. If the loss is trifling, he will pass it over; if serious, he will send out his inspectors to trace it. Thus there could be no long continued leakage, misuse, or robbery of the air, without the company becoming aware of the fact, and so being enabled to take measures to stop or prevent it. The foregoing are absolutely essential adjuncts to any scheme of public motive power supply by compressed air, without which we should be working in the dark, and could never be sure whether the company were losing or making money. With them, we know where we are and what we are doing.

Referring to the estimates given in Table I., I may explain that the item of repairs and renewals covers 10 per cent. on boilers and gas producers, 5 per cent. on engines, 5 per cent. on buildings, and 5 per cent. on mains. Considering that the estimates include ample fitting shops, with the best and most suitable tools, and that the wages list includes a staff of men whose chief work would be to attend to repairs, etc., I think the above allowances ample. Each item also includes 5 per cent. for contingencies.

I have commenced by giving all the preceding detail, in order to show the groundwork on which I base the estimate of the cost of compressed air power to consumers, in terms of indicated horse power per annum, as given in Table II. I may say that, in estimating the engine power and coal consumption, I have not, as in the original report, made purely theoretical calculations, but have taken diagrams from engines in actual use (although of somewhat smaller size than those intended to be employed), and have worked out the results therefrom. It will, I hope, be seen that, with all the safeguards we have provided, we may fairly reckon upon having for sale the stated quantity of air produced by means of the plant, as estimated, and at the specified annual cost; and that therefore the statement of cost per indicated horse power per annum may be fairly relied upon. Thus the cost of compressed air to the consumer, based upon an _average_ charge of 5d. per 1,000 cubic feet, will vary from £6 14s. per indicated horse power per annum to £18 13s. 3d., according to circumstances and mode of application.

A compressed air motor is an exceedingly simple machine--much simpler than an ordinary steam engine. But the air may also be used in an ordinary steam engine; and in this case it can be much simplified in many details. Very little packing is needed, as there is no nuisance from gland leakage; the friction is therefore very slight. Pistons and glands are packed with soapstone, or other self-lubricating packing; and no oil is required except for bearings, etc. The company will undertake the periodical inspection and overhauling of engines supplied with their power, all which is included in the estimates. The total cost to consumers, with air at an average of 5d. per 1,000 cubic feet, may therefore be fairly taken as follows:

Min. Max.
Cost of air used £6 14 0½ £18 13 3
Oil. waste, packing, etc. 1 0 0 1 0 0
Interest, depreciation,
etc., 12½ per cent. on
£10, the cost of engine
per indicated
horse power 1 5 0 1 5 0
-------- ---------
£8 19 0½ £20 18 3

The maximum case would apply only to direct acting engines, such as Tangye pumps, air power hammers, etc., where the air is full on till the end of the stroke, and where there is no expansion. The minimum given is at the average rate of 5d. per 1,000 cubic feet; but as there will be rates below this, according to a sliding scale, we may fairly take it that the lowest charge will fall considerably below £6 per indicated horse power per annum.--_Journal of Gas Lighting_.

* * * * *

THE BERTHON COLLAPSIBLE CANOE.

An endeavor has often been made to construct a canoe that a person can easily carry overland and put into the water without aid, and convert into a sailboat. The system that we now call attention to is very well contrived, very light, easily taken apart, and for some years past has met with much favor.

Mr. Berthon's canoes are made of impervious oil-skin. Form is given them by two stiff wooden gunwales which are held in position by struts that can be easily put in and taken out. The model shown in the figure is covered with oiled canvas, and is provided with a double paddle and a small sail. Fig. 2 represents it collapsed and being carried overland.

Mr. Berthon is manufacturing a still simpler style, which is provided with two oars, as in an ordinary canoe. This model, which is much used in England by fishermen and hunters, has for several years past been employed in the French navy, in connection with movable defenses. At present, every torpedo boat carries one or two of these canoes, each composed of two independent halves that may be put into the water separately or be joined together by an iron rod.

These boats ride the water very well, and are very valuable for exploring quarters whither torpedo boats could not adventure without danger.[1]--_La Nature_.

[Footnote 1: For detailed description see SUPPLEMENT, No. 84.]

* * * * *

THE FIFTIETH ANNIVERSARY OF THE OPENING OF THE FIRST GERMAN STEAM RAILROAD.

There was great excitement in Nürnberg on the 7th of December, 1835, on which day the first German railroad was opened. The great square on which the buildings of the Nürnberg and Furth "Ludwig's Road" stood, the neighboring streets, and, in fact, the whole road between the two cities, was filled with a crowd of people who flocked from far and near to see the wonderful spectacle. For the first time, a railroad train filled with passengers was to be drawn from Nürnberg to Furth by the invisible power of the steam horse. At eight o'clock in the morning, the civil and military authorities, etc., who took part in the celebration were assembled on the square, and the gayly decorated train started off to an accompaniment of music, cannonading, cheering, etc. Everything passed off without an accident; the work was a success. The engraving in the lower right-hand corner represents the engine and cars of this road.

It will be plainly seen that such a revolution could not be accomplished easily, and that much sacrifice and energy were required of the leaders in the enterprise, prominent among whom was the merchant Johannes Scharrer, who is known as the founder of the "Ludwig's Road."

One would naturally suppose that such an undertaking would have met with encouragement from the Bavarian Government, but this was not the case. The starters of the enterprise met with opposition on every side; much was written against it, and many comic pictures were drawn showing accidents which would probably occur on the much talked of road. Two of these pictures are shown in the accompanying large engraving, taken from the _Illustrirte Zeitung_. As shown in the center picture, right hand, it was expected by the railway opponents that trains running on tracks at right angles must necessarily come in collision. If anything happened to the engine, the passengers would have to get out and push the cars, as shown at the left.

Much difficulty was experienced in finding an engineer capable of attending to the construction of the road; and at first it was thought that it would be best to engage an Englishman, but finally Engineer Denis, of Munich, was appointed. He had spent much time in England and America studying the roads there, and carried on this work to the entire satisfaction of the company.

All materials for the road were, as far as possible, procured in Germany; but the idea of building the engines and cars there had to be given up, and, six weeks before the opening of the road, Geo. Stephenson, of London, whose engine, Rocket, had won the first prize in the competitive trials at Rainhill in 1829, delivered an engine of ten horse power, which is still known in Nürnberg as "Der Englander."

Fifty years have passed, and, as Johannes Scharrer predicted, the Ludwig's Road has become a permanent institution, though it now forms only a very small part of the network of railroads which covers every portion of Germany. What changes have been made in railroads during these fifty years! Compare the present locomotives with the one made by Cugnot in 1770, shown in the upper left-hand cut, and with the work of the pioneer Geo. Stephenson, who in 1825 constructed the first passenger railroad in England, and who established a locomotive factory in Newcastle in 1824. Geo. Stephenson was to his time what Mr. Borsig, whose great works at Moabit now turn out from 200 to 250 locomotives a year, is to our time.

Truly, in this time there can be no better occasion for a celebration of this kind than the fiftieth anniversary of the opening of the first German railroad, which has lately been celebrated by Nürnberg and Furth.

The lower left-hand view shows the locomotive De Witt Clinton, the third one built in the United States for actual service, and the coaches. The engine was built at the West Point Foundry, and was successfully tested on the Mohawk and Hudson Railroad between Albany and Schenectady on Aug. 9, 1831.

* * * * *

IMPROVED COAL ELEVATOR.

An illustration of a new coal elevator is herewith presented, which presents advantages over any incline yet used, so that a short description may be deemed interesting to those engaged in the coaling and unloading of vessels. The pen sketch shows at a glance the arrangement and space the elevator occupies, taking less ground to do the same amount of work than any other mode heretofore adopted, and the first cost of erecting is about the same as any other.

When the expense of repairing damages caused by the ravages of winter is taken into consideration, and no floats to pump out or tracks to wash away, the advantages should be in favor of a substantial structure.

The capacity of this hoist is to elevate 80,000 bushels in ten hours, at less than one-half cent per bushel, and put coal in elevator, yard, or shipping bins.

The endless wire rope takes the cars out and returns them, dispensing with the use of train riders.

A floating elevator can distribute coal at any hatch on steam vessels, as the coal has to be handled but once; the hoist depositing an empty car where there is a loaded one in boat or barge, requiring no swing of the vessel.

Mr. J.R. Meredith, engineer, of Pittsburg, Pa., is the inventor and builder, and has them in use in the U.S. engineering service.--_Coal Trade Journal_.

* * * * *

STEEL-MAKING LADLES.

The practice of carrying melted cast iron direct from the blast furnace to the Siemens hearth or the Bessemer converter saves both money and time. It has rendered necessary the construction of special plant in the form of ladles of dimensions hitherto quite unknown. Messrs. Stevenson & Co., of Preston, make the construction of these ladles a specialty, and by their courtesy, says _The Engineer_, we are enabled to illustrate four different types, each steel works manager, as is natural, preferring his own design. Ladles are also required in steel foundry work, and one of these for the Siemens-Martin process is illustrated by Fig. 1. These ladles are made in sizes to take from five to fifteen ton charges, or larger if required, and are mounted on a very strong carriage with a backward and forward traversing motion, and tipping gear for the ladle. The ladles are butt jointed, with internal cover strips, and have a very strong band shrunk on hot about half way in the depth of the ladle. This forms an abutment for supporting the ladle in the gudgeon band, being secured to this last by latch bolts and cotters. The gearing is made of cast steel, and there is a platform at one end for the person operating the carriage or tipping the ladle. Stopper gear and a handle are fitted to the ladles to regulate the flow of the molten steel from the nozzle at the bottom.

Fig. 2 shows a Spiegel ladle, of the pattern used at Cyfarthfa. It requires no description. Fig. 3 shows a tremendous ladle constructed for the North-Eastern Steel Company, for carrying molten metal from the blast furnace to the converter. It holds ten tons with ease. It is an exceptionally strong structure. The carriage frame is constructed throughout of 1 in. wrought-iron plated, and is made to suit the ordinary 4 ft. 8½ in. railway gauge. The axle boxes are cast iron, fitted with gun-metal steps. The wheels are made of forged iron, with steel tires and axles. The carriage is provided with strong oak buffers, planks, and spring buffers; the drawbars also have helical compression springs of the usual type. The ladle is built up of ½ in. wrought-iron plates, butt jointed, and double riveted butt straps. The trunnions and flange couplings are of cast steel. The tipping gear, clearly shown in the engraving, consists of a worm and wheel, both of steel, which can be fixed on either side of the ladle as may be desired. From this it will be seen that Messrs. Stevenson & Co. have made a thoroughly strong structure in every respect, and one, therefore, that will commend itself to most steel makers. We understand that these carriages are made in various designs and sizes to meet special requirements. Thus, Fig. 4 shows one of different design, made for a steel works in the North. This is also a large ladle. The carriage is supported on helical springs and solid steel wheels. It will readily be understood that very great care and honesty of purpose is required in making these structures. A breakdown might any moment pour ten tons of molten metal on the ground, with the most horrible results.

* * * * *

APPARATUS FOR DEMONSTRATING THAT ELECTRICITY DEVELOPS ONLY ON THE SURFACE OF CONDUCTORS.

Mr. K.L. Bauer, of Carlsruhe, has just constructed a very simple and ingenious apparatus which permits of demonstrating that electricity develops only on the surface of conductors. It consists (see figure) essentially of a yellow-metal disk, M, fixed to an insulating support, F, and carrying a concentric disk of ebonite, H. This latter receives a hollow and closed hemisphere, J, of yellow metal, whose base has a smaller diameter than that of the disk, H, and is perfectly insulated by the latter. Another yellow-metal hemisphere, S, open below, is connected with an insulating handle, G. The basal diameter of this second hemisphere is such that when the latter is placed over J its edge rests upon the lower disk, M. These various pieces being supposed placed as shown in the figure, the shell, S, forms with the disk, M, a hollow, closed hemisphere that imprisons the hemisphere, J, which is likewise hollow and closed, and perfectly insulated from the former.

The shell, S, is provided internally with a curved yellow-metal spring, whose point of attachment is at B, and whose free extremity is connected with an ebonite button, K, which projects from the shell, S. By pressing this button, a contact may be established between the external hemisphere (formed of the pieces, S and M), and the internal one, J. As soon as the button is left to itself, the spring again begins to bear against the interior surface of S, and the two hemispheres are again insulated.

The experiment is performed in this wise: The shell, S, is removed. Then a disk of steatite affixed to an insulating handle is rubbed for a few instants with a fox's "brush," and held near J until a spark occurs. Then the apparatus is grasped by the support, F, and an elder-pith ball suspended by a flaxen thread from a good conducting support is brought near J. The ball will be quickly repelled, and care must be taken that it does not come into contact with J. After this the apparatus is placed upon a table, the shell, S, is taken by its handle, G, and placed in the position shown in the figure, and a momentary contact is established between the two hemispheres by pressing the button, K. Then the shell, S, is lifted, and the disk, M, is touched at the same time with the other hand. If, now, the pith ball be brought near S, it will be quickly repelled, while it will remain stationary if it be brought near J, thus proving that all the electricity passed from J to S at the moment of contact.--_La Lumiere Electrique_.

* * * * *

THE COLSON TELEPHONE.

This apparatus has recently been the object of some experiments which resulted in its being finally adopted in the army. We think that our readers will read a description of it with interest. Its mode of construction is based upon a theoretic conception of the lines of force, which its inventor explains as follows in his Elementary Treatise on Electricity:

"To every position of the disk of a magnetic telephone with respect to the poles of the magnet there corresponds a certain distribution of the lines of force, which latter shift themselves when the disk is vibrating. If the bobbin be met by these lines in motion, there will develop in its wire a difference of potential that, according to Faraday's law, will be proportional to their number. All things equal, then, a telephone transmitter will be so much the more potent in proportion as the lines set in motion by the vibrations of the disk and meeting the bobbin wire are greater in number. In like manner, a receiver will be so much the more potent in proportion as the lines of force, set in motion by variations in the induced currents that are traversing the bobbin and meeting the disk, are more numerous. It will consequently be seen that, generally speaking, it is well to send as large a number of lines of force as possible through the bobbin."

In order to obtain such a result, the thin tin-plate disk has to be placed between the two poles of the magnet. The pole that carries the fine wire bobbin acts at one side and in the center of the disk, while the other is expanded at the extremity and acts upon the edge and the other side. This pole is separated from the disk by a copper washer, and the disk is thus wholly immersed in the magnetic field, and is traversed by the lines of force radiatingly.

This telephone is being constructed by Mr. De Branville, with the greatest care, in the form of a transmitter (Fig. 2) and receiver (Fig. 3). At A may be seen the magnet with its central pole, P, and its eccentric one, P'. This latter traverses the vibrating disk, M, through a rubber-lined aperture and connects with the soft iron ring, F, that forms the polar expansion. These pieces are inclosed in a nickelized copper box provided with a screw cap, C. The resistance of both the receiver and transmitter bobbin is 200 ohms.

The transmitter is 3½ in. in diameter, and is provided with a re-enforcing mouthpiece. It is regulated by means of a screw which is fixed in the bottom of the box, and which permits of varying the distance between the disk and the core that forms the central pole of the magnet. The regulation, when once effected, lasts indefinitely. The regulation of the receiver, which is but 2¼ in. in diameter, is performed once for all by the manufacturer. One of the advantages of this telephone is that its regulation is permanent. Besides this, it possesses remarkable power and clearness, and is accompanied with no snuffling sounds, a fact doubtless owing to all the molecules of the disk being immersed in the magnetic field, and to the actions of the two poles occurring concentrically with the disk. As we have above said, this apparatus is beginning to be appreciated, and has already been the object of several applications in the army. The transmitter is used by the artillery service in the organization of observatories from which to watch firing, and the receiver is added to the apparatus pertaining to military telegraphy. The two small receivers are held to the lens of the operator by the latter's hat strap, while the transmitter is suspended in a case supported by straps, with the mouthpieces near the face (Fig. 1).

In the figure, the case is represented as open, so as to show the transmitter. The empty compartment below is designed for the reception and carriage of the receivers, straps, and flexible cords. This arrangement permits of calling without the aid of special apparatus, and it has also the advantage of giving entire freedom to the man on observation, this being something that is indispensable in a large number of cases.

In certain applications, of course, the receivers may be combined with a microphone; yet on an aerial as well as on a subterranean line the transmitter produces effects which, as regards intensity and clearness, are comparable with those of a pile transmitter.

Stations wholly magnetic may be established by adding to the transmitter and two receivers a Sieur phonic call, which will actuate them powerfully, and cause them to produce a noise loud enough for a call. It would be interesting to try this telephone on a city line, and to a great distance on those telegraph lines that are provided with the Van Rysselberghe system. Excellent results would certainly be obtained, for, as we have recently been enabled to ascertain, the voice has a remarkable intensity in this telephone, while at the same time perfectly preserving its quality.--_La Nature_.

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[NATURE.]

THE MELDOMETER.

The apparatus which I propose to call by the above name ([mu][epsilon][lambda][delta][omega], to melt) consists of an adjunct to the mineralogical microscope, whereby the melting-points of minerals may be compared or approximately determined and their behavior watched at high temperatures either alone or in the presence of reagents.

As I now use it, it consists of a narrow ribbon of platinum (2 mm. wide) arranged to traverse the field of the microscope. The ribbon, clamped in two brass clamps so as to be readily renewable, passes bridgewise over a little scooped-out hollow in a disk of ebony (4 cm. diam.). The clamps also take wires from a battery (3 Groves cells); and an adjustable resistance being placed in circuit, the strip can be thus raised in temperature up to the melting-point of platinum.

The disk being placed on the stage of the microscope the platinum strip is brought into the field of a 1" objective, protected by a glass slip from the radiant heat. The observer is sheltered from the intense light at high temperatures by a wedge of tinted glass, which further can be used in photometrically estimating the temperature by using it to obtain extinction of the field. Once for all approximate estimations of the temperature of the field might be made in terms of the resistance of the platinum strip, the variation of such resistance with rise of temperature being known. Such observations being made on a suitably protected strip might be compared with the wedge readings, the latter being then used for ready determinations. Want of time has hindered me from making such observations up to this.

The mineral to be experimented on is placed in small fragments near the center of the platinum ribbon, and closely watched while the current is increased, till the melting-point of the substance is apparent. Up to the present I have only used it comparatively, laying fragments of different fusibilities near the specimen. In this way I have melted beryl, orthoclase, and quartz. I was much surprised to find the last mineral melt below the melting-point of platinum. I have, however, by me as I write, a fragment, formerly clear rock-crystal, so completely fused that between crossed Nicols it behaves as if an amorphous body, save in the very center where a speck of flashing color reveals the remains of molecular symmetry. Bubbles have formed in the surrounding glass.

Orthoclase becomes a clear glass filled with bubbles: at a lower temperature beryl behaves in the same way.

Topaz whitens to a milky glass--apparently decomposing, throwing out filmy threads of clear glass and bubbles of glass which break, liberating a gas (fluorine?) which, attacking the white-hot platinum, causes rings of color to appear round the specimen. I have now been using the apparatus for nearly a month, and in its earliest days it led me right in the diagnosis of a microscopical mineral, iolite, not before found in our Irish granite, I think. The unlooked-for characters of the mineral, coupled with the extreme minuteness of the crystals, led me previously astray, until my meldometer fixed its fusibility for me as far above the suspected bodies.

Carbon slips were at first used, as I was unaware of the capabilities of platinum.

A form of the apparatus adapted, at Prof. Fitzgerald's suggestion, to fit into the lantern for projection on the screen has been made for me by Yeates. In this form the heated conductor passes both below and above the specimen, which is regarded from a horizontal direction.

J. JOLY.

Physical Laboratory, Trinity College, Dublin.

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[AMERICAN ANNALS OF THE DEAF AND DUMB.]

TOUCH TRANSMISSION BY ELECTRICITY IN THE EDUCATION OF DEAF-MUTES.

Progress in electrical science is daily causing the world to open its eyes in wonder and the scientist to enlarge his hopes for yet greater achievements. The practical uses to which this subtile fluid, electricity, is being put are causing changes to be made in time-tested methods of doing things in domestic, scientific, and business circles, and the time has passed when startling propositions to accomplish this or that by the assistance of electricity are dismissed with incredulous smiles. This being the case, no surprise need follow the announcement of a device to facilitate the imparting of instruction to deaf children which calls into requisition some service from electricity.

The sense of touch is the direct medium contemplated, and it is intended to convey, with accuracy and rapidity, messages from the operator (the teacher) to the whole class simultaneously by electrical transmission.[1]

[Footnote 1: By the same means two deaf-mutes, miles apart, might converse with each other, and the greatest difficulty in the way of a deaf-mute becoming a telegraph operator, that of receiving messages, would be removed. The latter possibilities are incidentally mentioned merely as of scientific interest, and not because of their immediate practical value. The first mentioned use to which the device may be applied is the one considered by the writer as possibly of practical value, the consideration of which suggested the appliance to him.]

An alphabet is formed upon the palm of the left hand and the inner side of the fingers, as shown by the accompanying cut, which, to those becoming familiar with it, requires but a touch upon a certain point of the hand to indicate a certain letter of the alphabet.

A rapid succession of touches upon various points of the hand is all that is necessary in spelling a sentence. The left hand is the one upon which the imaginary alphabet is formed, merely to leave the right hand free to operate without change of position when two persons only are conversing face to face.

The formation of the alphabet here figured is on the same principle as one invented by George Dalgarno, a Scottish schoolmaster, in the year 1680, a cut of which maybe seen on page 19 of vol. ix. of the _Annals_, accompanying the reprint of a work entitled "_Didascalocophus_." Dalgarno's idea could only have been an alphabet to be used in conversation between two persons _tête à tête_, and--except to a limited extent in the Horace Mann School and in Professor Bell's teaching--has not come into service in the instruction of deaf-mutes or as a means of conversation. There seems to have been no special design or system in the arrangement of the alphabet into groups of letters oftenest appearing together, and in several instances the proximity would seriously interfere with distinct spelling; for instance, the group "u," "y," "g," is formed upon the extreme joint of the little finger. The slight discoverable system that seems to attach to his arrangement of the letters is the placing of the vowels in order upon the points of the fingers successively, beginning with the thumb, intended, as we suppose, to be of mnemonic assistance to the learner. Such assistance is hardly necessary, as a pupil will learn one arrangement about as rapidly as another. If any arrangement has advantage over another, we consider it the one which has so grouped the letters as to admit of an increased rapidity of manipulation. The arrangement of the above alphabet, it is believed, does admit of this. Yet it is not claimed that it is as perfect as the test of actual use may yet make it. Improvements in the arrangement will, doubtless, suggest themselves, when the alterations can be made with little need of affecting the principle.

In order to transmit a message by this alphabet, the following described appliance is suggested: A matrix of cast iron, or made of any suitable material, into which the person receiving the message (the pupil) places his left hand, palm down, is fixed to the table or desk. The matrix, fitting the hand, has twenty-six holes in it, corresponding in position to the points upon the hand assigned to the different letters of the alphabet. In these holes are small styles, or sharp points, which are so placed as but slightly to touch the hand. Connected with each style is a short line of wire, the other end of which is connected with a principal wire leading to the desk of the operator (the teacher), and there so arranged as to admit of opening and closing the circuit of an electric current at will by the simple touch of a button, and thereby producing along the line of that particular wire simultaneous electric impulses, intended to act mechanically upon all the styles connected with it. By these impulses, produced by the will of the sender, the styles are driven upward with a quick motion, but with only sufficient force to be felt and located upon the hand by the recipient. Twenty-six of these principal or primary wires are run from the teacher's desk (there connected with as many buttons) under the floor along the line of pupils' desks. From each matrix upon the desk run twenty-six secondary wires down to and severally connecting with the twenty-six primary wires under the floor. The whole system of wires is incased so as to be out of sight and possibility of contact with foreign substances. The keys or buttons upon the desk of the teacher are systematically arranged, somewhat after the order of those of the type writer, which allows the use of either one or both hands of the operator, and of the greatest attainable speed in manipulation. The buttons are labeled "a," "b," "c," etc., to "z," and an electric current over the primary wire running from a certain button (say the one labeled "a") affects only those secondary wires connected with the styles that, when excited, produce upon the particular spot of the hands of the receivers the tactile impression to be interpreted as "a." And so, whenever the sender touches any of the buttons on his desk, immediately each member of the class feels upon the palm of his hand the impression meant to be conveyed. The contrivance will admit of being operated with as great rapidity as it is probable human dexterity could achieve, i.e., as the strokes of an electric bell. It was first thought of conveying the impressions directly by slight electric shocks, without the intervention of further mechanical apparatus, but owing to a doubt as to the physical effect that might be produced upon the persons receiving, and as to whether the nerves might not in time become partly paralyzed or so inured to the effect as to require a stronger and stronger current, that idea was abandoned, and the one described adopted. A diagram of the apparatus was submitted to a skillful electrical engineer and machinist of Hartford, who gave as his opinion that the scheme was entirely feasible, and that a simple and comparatively inexpensive mechanism would produce the desired result.

The matter now to consider, and the one of greater interest to the teacher of deaf children, is, Of what utility can the device be in the instruction of deaf-mutes? What advantage is there, not found in the prevailing methods of communication with the deaf, i.e., by gestures, dactylology, speech and speech-reading, and writing?

I. The language of gestures, first systematized and applied to the conveying of ideas to the deaf by the Abbe de l'Epee during the latter part of the last century, has been, in America, so developed and improved upon by Gallaudet, Peet, and their successors, as to leave but little else to be desired for the purpose for which it was intended. The rapidity and ease with which ideas can be expressed and understood by this "language" will never cease to be interesting and wonderful, and its value to the deaf can never fail of being appreciated by those familiar with it. But the genius of the language of signs is such as to be in itself of very little, if any, direct assistance in the acquisition of syntactical language, owing to the diversity in the order of construction existing between the English language and the language of signs. Sundry attempts have been made to enforce upon the sign-language conformity to the English order, but they have, in all cases known to the writer, been attended with failure. The sign-language is as immovable as the English order, and in this instance certainly Mahomet and the mountain will never know what it is to be in each other's embrace. School exercises in language composition are given with great success upon the basis of the sign-language. But in all such exercises there must be a translation from one language to the other. The desideratum still exists of an increased percentage of pupils leaving our schools for the deaf, possessing a facility of expression in English vernacular. This want has been long felt, and endeavoring to find a reason for the confessedly low percentage, the sign-language has been too often unjustly accused. It is only when the sign-language is abused that its merit as a means of instruction degenerates. The most ardent admirers of a proper use of signs are free to admit that any excessive use by the pupils, which takes away all opportunities to express themselves in English, is detrimental to rapid progress in English expression.