Class X.]

ELECTRO-M AGNETIC ENGINES, &c.; ELECTRIC TELEGRAPHS.

2S.3

5th. The larger the iron plates, and the greater thepower of the battery, the greater is the economy of thisengine.

Kxigut and Sons (Xo. 453, pp. 4G2, 403) exhibit anelectro-magnetic engine. This is probably the simplestform by which an electric current can be made to workby its action on permanent magnets, though not themost effective. Four coil-magnets are fixed rectangu-larly on an axis, and revolve within a circle formed offour fixed magnetized quadrants. The contacts are madeand broken by rubbing springs on an axis (so it appearedon examination); the nicety of construction consisting inthe adjustment of the moments of union and disruption,so as to obtain an effective difference of action always inthe direction between the two opposite poles of the per-manent magnet.

Knight also exhibits another electrical machine, inwhich a bar is alternately pushed and pulled, and soworking on a crank and turning a fly-wheel. In allthese machines the mechanism itself provides for thenecessary alternate making and breaking of the circuits.It is probable that little power is obtained, for thegreatest care appears to have been taken to destroy fric-tion, by making the fly-axis revolve on friction-rollers.

Watkins and Hill (Xo. 659, p. 466*) have exhibitedan electro-magnetic engine. Two horse-shoe electro-magnets are alternately excited by two electric currents,and each as it becomes a magnet attracts one of the armsof a rectangularly bent iron bar, which is thus kept in astate of oscillation round a pivot from one magnet tothe other. The ends of the bar carry rods working onjoints which are connected with cranks rectangularlyplaced on an axis. Thus the dead point of one crankcoincides with the quiescent state of its own magnet andwith the active state of the other, and the axis is main-tained in rotation with its fly-wheel. The magnet, bars,and crank are so arranged along the axis as to give roomfor the cranks, of which there are two, though, in fact,there might be any number of magnets and cranks work-ing simultaneously.

The alternation of the circuit is kept up by a me-chanism worked by the machine itself.

Allen (Xo- 413, p. 454) exhibits an electro-magneticrailway-train alarm; it consists of a copper chain, in-tended to be placed over every carriage, the connectionbetween each being established by the guard-chains; onthe circuit being completed, the ordinary steam-whistledischarges the steam. The arrangements are as simpleas well can be.

Cresswell (Xo. 417, p. 454) exhibits an electro-mag-netic engine for the production of motion; it consists oftwo pair of electro-magnets, between which a keepervibrates and communicates motion to a wheel and crank.

Froment (France , No. 1609, p. 1254) exhibits anelectro-magnet acting alternately, by elevating a lever,which communicates motion to a crank. lie also ex-hibits a circular arrangement of coils, two of which arein action successively.

Breton (France , No. 1113, p. 1231) exhibits an electro-medical apparatus with a double current; but as this instru-ment is intended for medical purposes, and not as a motivepower, it scarcely falls within the province of this Jury.

Hjorth (Denmark , No. 47, pp. 1359, 1360) has ex-hibited an electro-magnetic engine. It consists of twosets of hollow horse-shoe electro-magnets, conical inside,with a corresponding number of solid electro-magnets,which, by mutually attracting each other, make a doublestroke of 4 inches in length. The power has been found,by means of a spring-balance, to be about 30 lbs. at thecommencement of the stroke, when the distance of therespective poles is about half an inch, decreasing slightlyby degrees as the piston enters the hollow electro-magnet.The current is broken by the end of each stroke, and thedestroying effect of the spark prevented by moistening thesurface of communication with diluted sulphuric acid;no repelling power is applied.

Mr. Hjorth also exhibits a diagram and plan for animproved arrangement, consisting of only one hollowelectro-magnet, the respective poles of which are dividedinto three or more square rings, which are somewhat

conical inside, and are connected outside with the arma-tures (?) of the magnet, which form the connection be-tween the respective poles. From the upper and lowerpart of the arrangement extend withinside four iron plateswith ribs, which in the centre are connected with corre-sponding diamagnetic plates and ribs. These plates areapplied for guiding the motion of the piston, and serve atthe same time as a means by which metallic contact mayduring each stroke be established and broken between thepiston and any one of the respective plates. For this'pur-pose, four pairs of rollers are placed withinside the pistonor hollow shafts, which are arranged on the fourway-cock principle, with a ring inlaid with a diamagneticmetal between the rings and shafts, that the magneticbearings may be brought into contact either with thesimilar or diamagnetic parts of the same rings.

The required motion of these rings is produced by smallcranks inside the piston, joined to the connecting-rod insuch manner that each pair of cranks moves in oppositedirections.

Whilst the engine makes a down stroke, magneticcontact is established between the north pole and piston;the polarity thus acquired causes it to attract the southpole. When the down stroke is performed, the magneticcontact between the north pole and the piston is brokenby turning the upper pair of cranks in one direction,whilst similar contact is established between the southpole and piston by moving the lower pair of cranks inthe opposite direction. A reciprocal motion being ob-tained in the above maimer, the electric current passescontinuously in one direction round the piston and eachof the poles, the motion of the piston being reversed bysimply breaking and establishing magnetic contact. Onthe piston passing out of the one pole it enters the other,and induces thereby, according to the law of the secondarycurrents, two currents in opposite directions, and thusboth are neutralized. The advantages assumed are:—

1st. The obtaining a stroke of any length with onehollow electro-magnet, the piston being a moveable ex-tension of either of the poles, attracted by a succession ofpolarities, the acting surfaces of which extend to thewhole circumference.

2nd. The arranging the piston in such manner that itmay be extended to any size, without its being heavierthan a piston in a low-power steam-engine of the same size,the power being expressed in pounds per square inch.

3rd. A prevention of the destroying effect of theelectric spark.

4th. A neutralization of the secondary currents and aprevention of their reaction.

The following table, as obtained by Mr. Hjorth, showsthe attractive power obtained with a horizontal electro-magnetic engine of 16 inches stroke, the poles of themoveable magnet being separated C inches, or, in otherwords, the piston being 6 inches square:—

Distance

Indies.

(!)

The

lbs.

f 7280

of the

hi

attractive <

98

respective

force was |

140

poles.

1 1 >

1* 160

And theangle ofmagneticforce was

A Prize Medal was awarded to Mr. Hjorth.

75-58

72-39

67-22

50-12

42-34

Electric Telegraphs.

As might have been expected, there are exhibitedvoltaic batteries; galvanometers: electro-magnets; tele-graph wires; wires for submarine purposes; printingtelegraphs: in fact, the Exhibition is rich with a largenumber of very ingenious contrivances, applicable to everystage of electric telegraphic communication.

The Electric Telegraph Company, which was esta-blished in the year 1846, have evidently used muchdiligence in possessing themselves of numerous patents,commencing with Cooke and Wheatstone’s five-needletelegraph, patented in 1837, up to the present time. Inthe fine collection they exhibit are some of the mostvaluable inventions, in point of real practical utility, thathave yet occurred; but they include also many forms oftelegraph which, judging from their not being made use