812 KBPORT— 1886. 



ment of the beam five minutes of angle. The lantern would be 10 feet diameter, 

 ■with bent plate glass. The cost of the whole described would be materially less 

 than the cost of a first-order light and lantern with oil lamps and large burners. 

 In fine weather the small engine would be used. Its effective power on the brake 

 is fully li horse-power ; from this 1^ horse-power the dynamo machine produces 

 considerably over 800 watts — say, 800 watts — in the arc itself, or 28 amperes, 

 through a fairly long arc of 40 volts. Of course the value of this in candles 

 depends upon the colour in which it is measured and the direction in relation to 

 the axis of the carbons. In red light the mean over the sphere would certainly 

 exceed 1,200 candles. In clear weather, or in slight haze or in rain, the beam 

 of this light through the lenses would be much more powerful at the horizon and 

 on the distant sea than any single-focus light in oil or gas, or at least would be 

 fairly comparable with anything yet exhibited in oil or gas, whether triform or 

 quadriform. But on the nearer sea the illumination would be reduced, so that no 

 annoyance would be caused by dazzling flashes. In really thick weather, or, in- 

 deed, in any weather when there was a doubt as to the visibility at the horizon of 

 the lower power, the larger engine would be used, under the superintendence of the 

 second keeper. This engine will give 10 horse-power on the brake, and there is 

 difiiculty in getting 85 per cent, as useful electrical energy outside the machine — 

 that is, 6,340 watts. From this deduct 10 per cent, for the leads and the lamp and 

 for steadying the arc, leaving 5,710 watts in the arc itself, or 114 amperes, with 

 a diiference of potential of 50 volts. It hence follows from the South Foreland 

 experiments that in any fog whatever, the flashes would penetrate farther than any 

 existing gas or oil light. The increased size of crater compared with that produced 

 by the current of 20 amperes will give increased vertical divergence, and so 

 cause the maximum illumination to be attained at a less distance from the light- 

 house. The attendance of two men would sufiice for all the duties of a lighthouse, 

 because, under ordinary circumstances, one only need be on duty, excepting whilst 

 gas is being made. The usual course would be that, with the exception of from 

 two to three hours at the beginning of the night, the gas-producer would be 

 damped down, and when the small engine was at work the supply be taken from 

 the gas-holder. 



The consumption of coal would be 4 lbs. per hour of lighting, of water about 

 half a gallon, of carbon about 4 inches per hour, allowing for ends wasted. 

 Comparing with a first-order light illuminated with parafBne, the total charges 

 for maintenance would not dirt'er materially. The substantial advantage resulting 

 would be that, at a trifling cost per hour, there is available at any moment a light of 

 the greatest penetrative power. 



2. Multiplex Telegraphy. Bij W. H. Pkeece, F.B.8. 



The enormous increase of telegraphic business in England has necessitated new 

 modes of working to increase the capacity of wires for the conveyance of messages. 

 Delany's system enables six messages to be sent on one wire between London and 

 Birmingham at the same time. It is based on a system of distributing the use of the 

 wire for a very short interval several times a second to each telegraphist, so that the 

 currents sent to each, though they are intermittent and very much broken up, are 

 practically continuous. The distributors are maintained in absolute synchronism 

 by a very ingenious system of correction. The instrument used for telegraphing 

 is the ordinary apparatus already in use in England — the sounder. It is not a 

 long-distance system, for the introduction of disturbances due to underground 

 wires reduces its efficiency. Only four-way working is practicable between London 

 and Manchester at present. It will be very extensively used by the Post Ofiice. 



3. A portalle Meciric Lamp. By W. H. Preecb, F.B.S. 



The demand for a new safety-lamp in mines has directed many minds to the 

 application of electricity to this purpose. Some have proposed to use primary 



