June 1st, 18S7.] 



SCIENTIFIC NEWS. 



79 



accomplished fact in some places, but the ideal method of 

 transmission is by means of an electric wire, or some 

 equally convenient plan. The experiments made at Paris 

 some months ago by M. Deprez, seemed to promise a solu- 

 tion of the problem, lor he carried the power along wires 

 for thirty-five m.iles ; but the commercial efficiency of the 

 result was not more than forty-five per cent., so that it 

 would be cheaper to transport the potential energy in the 

 form of coal rather than in a kinetic form over the wires. 

 The great importance of this question brings forth some 

 new scheme nearly every week, and the most recent, 

 carried out near Zurich, promises well. The power to be 

 conveyed was a water force varying from thirty to fifty 

 horse-power, and the distance it had to be carried was some 

 five miles. Every care appears to have been taken in 

 making the experiment, and the results, measured both 

 electrically and mechanicallj', seem to be that seventy per 

 cent, of the power can be conveyed by means of copper 

 wires to the desired point. 



The Lighting of Manchester Exhibition. — The whole of 

 the extensive buildings and grounds are lighted by electricity, 

 there being over 600 arc and 3,000 glow lamps. The plan 

 adopted by the executive was to divide the incandescent 

 lighting into three sections : First, the Fine Art Galleries, 

 consisting of a series of rooms, with a total of 1,620 lamps ; 

 next, the Palm House of the Botanical Gardens, used as a 

 series of dining rooms, with 750 lamps ; and lastly, the 

 various quaint buildings, shops, and houses forming the 

 representation of " Old Manchester and Salford," with about 

 600 lamps. The mains are placed underneath the flooring 

 of the Exhibition until they reach the corner of the galleries 

 in the east nave, where they are carried up and along the 

 external brickwork of the galleries. Each room throughout 

 the galleries is connected with two of the circuits, so that 

 the lighting of each alternate .principal is from a different 

 main. In the event of any dynamo breaking down or any- 

 thing happening to any one circuit, the result would be to 

 diminish the number of lights by one half, the alternate 

 principals in the rooms being left fully lighted. As a point 

 of some interest, it may be noted that the length of all the 

 main cables used for the above-mentioned sections exceeds 

 nine miles, whilst the weight of the copper forming the con- 

 ductors (cables of 19-strand wire) is calculated at very 

 nearly 10 tons. Among the dynamos used, special interest 

 attaches to the four Edison machines, which are of the origi- 

 nal type, manufactured by Mr. Edison himself in New York 

 some six years ago. They are said to have been in daily 

 work, lighting the Theatre Royal, at Manchester, since 

 December, 1882, and during that time not to have worn 

 out a single pair of brushes, while no interruption has 

 occurred to them. 



Photographing by Phosphorescent Light has recently 

 been accomplished by Professor Zenger, of Prague. Whilst 

 watching Mont Blanc on a September evening in 1S83, he 

 was struck by the peculiar greenish-blue glow that con- 

 tinued to surround the summit after sunset until half past 

 ten. It looked as if both the snow and the limestone debris 

 were radiating a light of the beautiful azure blue charac- 

 teristic of the Lake of Geneva. The idea then suggested 

 itself to the Professor that it might be possible to photograph 

 with the help of these phosphorescent rays, which are 

 known to be highly actinic. After his return to Prague, he 

 made experiments in photographing phosphorescent objects 

 on a plate covered with a film of Balmain's luminous paint 

 instead of the ordinary collodion film. After exposure for 

 a few seconds the plate was brought in contact with an 

 ordinary dry plate in the dark, the latter plate not being 

 particularly sensitive ; and the development produced an 



image with all details. These encouraging preliminaries 

 induced Mr. Zenger to try photographing the picturesque 

 steeples and towers of Prague on a dark night. The plate 

 was exposed for fifteen minutes and then kept in contact 

 with the dry plate till the morning. The experiment proved 

 a complete success ; the buildings exposed during daytime 

 to the direct raj's of the sun gave off sufficient dark rays 

 (invisible to the human eye) during the night, so that the 

 phosphorescent plate was acted upon. After this Professor 

 Zenger exposed sheets of music for several hours to strong 

 sunlight, and then placed them over ordinary photographic 

 paper. The music and prints were well copied, the notes 

 and letters being distinct and black. 



Boiler Explosions. — Among some recent lectures in me- 

 chanical engineering given at Sibley College, in America, 

 there is one on " Steam Boiler Explosions," which is well 

 worthy of attention. The idea is still more or less prevalent, 

 among users of boilers, that after it has become overheated a 

 boiler can be exploded by the sudden admission of cold water. 

 Those who hold this opinion suppose that when the cold 

 water comes in contact with the overheated plates, steam is 

 produced so rapidly as to cause an immediate pressure 

 sufficient to burst the boiler. That this is an impossibility 

 has often been pointed out by competent authorities, and Mr. 

 Allen does good service in again calling attention to what in 

 all probability actually occurs. When there is too little 

 water in the boiler and it becomes over-heated, if water is 

 then pumped in, the plates and tubes are contorted and 

 strained, and the joints suffer also. Then when the pres- 

 sure rises the boiler is unable to resist and it bursts. The 

 true remedy in the case of overheating is to draw the fire, 

 and inspect the boiler when cold before subjecting it to pres- 

 sure. In common with others who have investigated the 

 subject, Mr. Allen has been struck with the fact that when 

 cylinders or other receptacles of steam fail, they are not 

 broken in peces nor do they burst with violence. As is 

 well known, the effect with boilers is usually very different, 

 and its cause is explained as follows : When a boiler cracks 

 the pressure is relieved, and if this is effected rapidly the 

 water being relieved of pressure is suddenly converted 

 into steam, with a great accession of bursting power, which 

 spends itself in breaking up the boiler and hurling the 

 pieces to great distances. 



The Purity of Mid-Atlantic Air. — In the course of an 

 address on the action of micro-organisms on surgical wounds, 

 Prof. F. S. Dennis, of New York, states that during his last trip 

 across the Atlantic he made some experiments to test the purity 

 of the air about 1,000 miles from land. He employed capsules of 

 sterilised gelatine, and exposed them for fifteen minutes. One 

 capsule was exposed in the state-room upon the main deck of 

 the steamer. Within eighteen hours over 500 points of infection 

 had developed. Two capsules exposed in a similar manner in 

 a cabin on the promenade deck, where the circulation of air 

 was free, showed ten days afterwards five or six points of in- 

 fection each. A capsule exposed over the bow of the ship was 

 found to be entirely uncontaminated. These experiments are 

 on the same lines as those of Pasteur and Tyndall upon the 

 mountair air of Switzerland, and, so far as they go, they show 

 the germless condition of mid-oceanic air, and also the need for 

 much more efficient ventilation in the state-rooms of even the 

 first-class American liners. — Lancet. 



Trichin.t, in Tork. — In the Eulenberg quaiterly journal of Foren- 

 sic Medicine official returns are given of the examination of pigs for 

 trichina; and measles in Prussia during the year 1SS5. According to 

 this no less than 4,421,208 pigs were examined, and of these 2,387 were 

 fcund " trichinous," sn that for every 1,852 pigs there was one trichi- 

 nous. The number of communities in which trichinous pigs were found 

 amounted to 849, and 13,653 pigs were suffering from measles. It is 

 also stated that loi American sides of bacon and bacon preparations 

 were found to contain trichince. These investigations were made by 

 21,117 official meat inspectors. 



