ELECTKICITY. 



Magnetic Experiments. Some singular ex- 

 periments in magnetism have been made by 

 Lord Lindsay with a very powerful magnet. 

 The poles of the magnet were 2 inches square 

 in sections, and the magnet was excited by a 

 30-cell Grove battery. The poles were kept 

 T 3 jr of an inch apart, and a half-crown piece 

 placed between them. When the magnet 

 was not excited, the coin dropped instantly 

 through ; but, when the magnet was charged, 

 the half-crown was 6 seconds in falling the dis- 

 tance of 2 inches. In a second experiment, 

 a small India-rubber tube, filled with mer- 

 cury, was placed between the poles, and an 

 electric current passed from the battery 

 through the mercury. The moment the mag- 

 net was excited the tube was set in motion, 

 getting away from between the poles, and as- 

 suming the shape of the letter S. On revers- 

 ing the current the shape of the curve was in- 

 stantly reversed. After this, a coil of copper 

 wire was placed round the vertical pole of a 

 magnet, and when the magnet was charged, 

 and a current of electricity sent through the 

 copper coils in one direction, the ring of fine 

 copper wire stuck fast in the magnet. On re- 

 versing the electric current, the ring jumped 

 off the pole of the magnet to some distance in 

 the air. In order to show the diamagnetic 

 properties of warm air, a lighted taper was 

 passejd through a hole bored along the poles of 

 the magnet, the ligh,t being brought to the 

 space of inch wide between the two poles. 

 So long as the magnet was excited, the light 

 burned brilliantly, the smoke coming out at 

 the extreme ends of the poles, and not rising 

 up directly off the flame. As soon, however, 

 as the magnet was discharged, the smoke rose 

 straight up and extinguished the flame. 



Dynamo-Electric Light. The London Times 

 gives an interesting account of a series of ex- 

 periments, conducted toward the close of the 

 year, at Sheerness, with a view of ascertaining 

 the applicability of Siemens's dynamo-electric 

 light to torpedo-service in time of war. The 

 light is produced by excessively rapid motion 

 generated from the fly-wheel of a steam-en- 

 gine, and operating on a powerful set of ordi- 

 nary galvanic coils in connection with soft 

 iron magnets. The leather strap from a four- 

 horse-power engine, encircling a small gun- 

 metal pinion, causes it to revolve with the 

 extreme velocity of 1,600 times a minute, in- 

 ducing motion in an electric bobbin at the 

 side of an apparatus consisting of several sets 

 of strong insulated coils. A stream of elec- 

 tricity consequently passes through them. This 

 stream is conducted to a second series of coils, 

 larger and more powerful than the first, which 

 are also in combination with a pinion revolv- 

 ing 800 times a minute, thus intensifying the 

 stream as it passes through them to a very 

 considerable degree. 



Both negative and positive currents are now alter- 

 nately given off from another " bobbin " at the side of 

 the second series of magnetic coils, to the train of in- 



sulated -wires, which conveys them to the position 

 from which the dynamo-electric light is to be ex- 

 hibited. Here there is a delicately-contrived appa- 

 ratus for containing the carbon-points, between winch 

 the light is to be generated, adjusted at the top of a 

 tripod somewhat similar in construction to that of a 

 surveying-instrument. At the back of the two car- 

 bon-points, and "slotted" vertically to admit of 

 their holders passing through it, is a concave reflect- 

 or of white polished metal, which collects the rays 

 of light into a focus, and transmits them in any re- 

 quired direction by means of an adjusting hand- 

 wheel below. A minute aperture in the centre of 

 the reflector, precisely behind the junction of the two 

 carbon-points, throws a representation of the flame 

 upon a piece of opal glass in a frame fixed at the 

 back of the reflector ; and, through the agency of an- 

 other small hand-wheel, which causes the carbon- 

 points to approach or recede from each other, the 

 flame can be reduced or intensified at pleasure, by 

 simply turning the wheel, care being taken at the 

 same time to keep a watchful eye upon the picture 

 produced, as the withdrawing of the points to too 

 great a distance from each other will extinguish the 

 light. It should have been remarked before that 

 ample means are taken, by lubricating the electrical 

 apparatus, to counteract the evil effects which might 

 otherwise arise from the excessive friction con- 

 sequent on the rapidity of motion in the several 

 parts. 



The object of instituting the series of experiments 

 was to ascertain if it was possible to throw such a 

 stream of light upon an enemy's working-parties, en- 

 gaged in interrupting communication with a line of 

 torpedoes at night, as would render them sufficiently 

 conspicuous to be fired at, and, consequently, driven 

 off. The place selected was the new fort at Garrison 

 Point, Sheerness. The engine and "coils" were 

 erected in the enclosure of the fort, while the instru- 

 ment itself was placed in one of the massive embra- 

 sures piercing its sides. No sooner was steam got up 

 and the order given to turn ahead, than the burring 

 noise of the machine indicated that electricity was 

 being rapidly generated, sparks and stars of vivid 

 blue light being given off at the various joints. An- 

 other instant, and a vivid stream of light shot across 

 the sea to a number of ships lying in the offing at a 

 distance of about two miles, lighting them up with 

 the brilliancy and distinctness of broad moonlight. 

 The effect was magnificent. Clouds of mists, ren- 

 dered visible by the intensity of the rays shooting 

 through them, rolled across the broad field of bright 

 light from time to time, not, however, interrupting 

 the view in their progress. By shifting the direc- 

 tion of the rays laterally, each object in turn came 

 within the compass of the portion of horizon ren- 

 dered clear. In fact, it was sufficiently apparent that 

 no objects of any appreciable size, such for instance 

 as an enemy's boats, could come within a mile or 

 more of one of Siemens's dynamo-electric instruments 

 in operation without being rendered conspicuous to 

 any battery in the vicinity, and, consequently, in- 

 volving to themselves the most imminent danger. 

 Hence the result of the experiments may be pro- 

 nounced a success ; whether, however, a correspond- 

 ing effect might not be obtained by a succession of 

 parachute-lights thrown from a rocket or mortar is 

 quite an open question. 



Electric Railway -Signals. Robinson's sys- 

 tem of electric railway-signals, recently intro- 

 duced, works automatically, and, it is said, 

 effectively. A train approaching a switch or 

 drawbridge in either direction, when distant 

 half a mile, presses on a lever in proximity to 

 the track. This lever controls an electric 

 circuit, which, being closed by the train, re- 

 mains closed. When a switch or drawbridge 

 is in place, and safe, a white flag is brought 



