i64 



SCIENTIFIC NE\VS. 



[Feb. 17, I E 



or over bad roads to the railway or water, it will be found 

 more useful. 



Of the lour branches of electric engineering dealt with 

 in this paper, electric lighting is the one which up to the 

 present has received most attention, called forth the 

 largest outlay of capital, and produced the most benefi- 

 cial results, if not to so great extent in this as in other 

 countries. 



As regards comfort, electric lighting proves itself 

 superior to all other methods of illumination, and its 

 convenience has caused it to be highly appreciated, but 

 in respect of economy, it does not as yet hold out the 

 same decided advantages. In incandescent lighting, the 

 cost of distribution is still heavy, though by increasing 

 the electromotive force and the efficiency of lamps it is 

 being much reduced. In arc lighting, the difficulty of 

 subdividing and of reducing the amount of light given by 

 one arc- lamp renders it expensive for general out-door 

 street illumination, as compared with the present low 

 prices of gas and oil. For the lighting of main streets 

 and railway stations, or other places where a concen- 

 trated light is required, the arc-light is beyond question 

 far cheaper than gas ; and its cost per candle-power is 

 but a very small fraction of that of gas. As the use of 

 electric lighting extends, the cost of working becomes 

 reduced ; installations which four years ago cost four- 

 pence per arc lamp per hour are now costing only two- 

 pence. 



In the United States there is hardly a city or town of 

 20,000 inhabitants which has not a central station for arc 

 or incandescent lamps ; and many towns of 3,000 to 

 4,000 are supporting them also. On the Continent large 

 central stations for electric lighting are already in 

 operation in competition with gas ; but there the price 

 of gas is generally two or three times what it is in this 

 country. 



Electric Metallurgy bids fair to become speedily of the 

 highest interest to engineers. The electro-chemical 

 separation of ores on a commercial scale by the electric 

 furnace has but recently been put to the test, chiefly in 

 obtaining aluminium from corundum, its richest ore. 

 Sir William Siemens first turned his attention to the 

 subject, but his death occurred before he had perfected 

 his invention. It was taken up by Messrs. Cowles, who 

 with the assistance of Professor Mabery have devised a 

 furnace, in which by the passage of powerful currents 

 the refractory ore is successfully reduced. The furnace* 

 is built of fire-brick, and lined with powdered char- 

 coal to withstand the intense heat ; it is in the 

 form of a box, 5 feet long, 12 inches wide, and 15 inches 

 deep. The current is conducted through the walls 

 and into the ore by means of a number of carbon rods, 3 

 inches diameter, and from 2 to 3 feet long. The positive 

 and negative carbons are introduced from opposite ends, 

 nearly meet in the centre. The ore, mixed with charcoal 

 and granulated copper, is put in so completely to sur- 

 round and cover the carbon. The furnace thus charged 

 is closed with a layer of charcoal and a lid lined with 

 firebrick; without the protection of some such refractory 

 material as charcoal the intense heat causes the firebricks 

 to run. When the furnace is ready, the current with an 

 electromotive force of 50 volts is turned on, and is 

 gradually increased up to some thousands of amperes. 

 In a few minutes the metal is melted around the elec- 

 trodes and these are then moved farther apart, until the 



* See Scientific News, Vol. i., p. 62. — First Series. 



current passes through the entire charge, and the whole 

 is in a molten condition ; the corundum becomes gradually 

 deoxidised, and the aluminium combining with the 

 copper, while the oxygen with the carbon escapes as 

 carbonic oxide ; about five hours suffice to complete the 

 reduction. 



The process of welding by electricity, introduced by 

 Professor Elihu Thomson, is similarly based upon the 

 passage of a powerful current between two electrodes. 

 In this case the two pieces of metal to be welded form 

 the electrodes ; they are brought together in close con- 

 tact, and as soon as the current is sent through the joint 

 its resistance causes intense heat until the weld is per- 

 fectly completed. The process is almost instantaneous, 

 and the heating occurs only at the joint; tempered steel 

 can thus be welded without in the least affecting its 

 hardness. 



Another plan of electric welding has been introduced 

 at St. Petersburg by Dr. Bernardo, in which the heat 

 necessary for fusion is caused by an arc. The current 

 is conducted to the weld by means of a carbon rod,, 

 which is connected by a flexible cable with the positive 

 terminal of a dynamo or battery, while the metal to be 

 welded is connected with the negative terminal. The 

 action of the arc set up by the flow of current from the 

 carbon to the metal may be likened to that of the blow- 

 pipe flame, except that the heating is more intense and 

 sudden, and is therefore more local. The reducing^ 

 action brought to bear on the metal keeps it clean and 

 unoxidised. 



SOCIETY OF ARTS. 

 At the meeting held on January 25th, Lord Sudeley 

 presiding, Mr. Walter Emden read a paper on " Theatres 

 and Fire-proof Construction." He described the "Aspha- 

 leian " stage now in use at the Royal Opera House,. 

 Budapest, and at the Stadt Theatre at Halle, in Germany., 

 This stage is composed of iron and masonry, the flooring 

 only of the stage being made of wood, and all the 

 mechanism is worked by hydraulic power. 



ALDERSHOT MILITARY SOCIETY. 

 On the 2nd inst.. Sir Henry Halford read a paper before 

 this Society, on the New Service Rifle, Lieutenant- 

 General Sir A. Alison being in the chair. The author 

 described the weapon about to be adopted, explaining 

 its various parts, and especially the magazine, which 

 will hold eight cartridges, is detachable, and can even be 

 cut off from the working while attached, so that the gun 

 can be used as a single loader. The reduction of the- 

 bore was stated to have lessened the trajectory, and so- 

 made shooting more accurate up to extreme ranges. 



MANCHESTER MICROSCOPICAL SOCIETY. 

 At the annual soiree held on the 28th ult.. Prof. Herdman 

 lectured upon the Life of a Sea Squirt, which was a small 

 gelatinous mass of irregular form, having a couple of open- 

 ings at its upper end, and if this little mass was touched it 

 sent forth from one of the openings a tiny jet of water 

 with considerable force. The lecturer described the 

 internal structure of one of these curious little animals,, 

 and then traced the history of its life from the very 

 beginnmg to the adult stage. He said that the young 

 ascidian was highly organised, but it degenerated as it 

 got older, and lived only for the purpose of eating and 

 breathing. 



