Jan. 30, 1885.] 



♦ KNOWLEDGE ♦ 



81 



of motion is 1 J tons, while the car which it propels weighs 

 2.V tons, or, when carrying the full number of passengers ( U>), 

 5i tons. When we "compare this weight with '.!iat of a 

 steam or compressed air locomotive (titlier ot which will 

 weigh from eight to ten tons to ilo *Lti same amount of 

 useful work), stored electrical energy has the advanfugo in 

 proportion of about to 1 so long as the propelling force is 

 directly proportional to the weight movrd." I>y mani- 

 pulating the hantile above refened to, the strength of the 

 current may be varied, and the speed, which ranges between 

 three and ten miles an hour, increased or decreased in a 

 considerablj- shorter distance than i,s possible with horse- 

 power; while, should necessity otlVr, a propelling power 

 equal to that of sLxteen horses may be applied at any 

 moment. 



The experimental line at Milwall is a difficult one. It 

 is made somewhat roughly, and has a total length of 100 ft,, 

 forming near its centre a right angle with an extremely 

 sharp curve, the radius being only 35 ft. One side of the 

 angle is tolerably level, but with the curve commences an 

 incline of 1 Ln 40, which gradualh- increases until it attains 

 a maximum of 1 in 17 at the end of the journey. This 

 steep incline has to be mounted without a run, a rush being 

 prevented by the sharpness of the curve. 



It is found that the driving batteries maintain a sufiicient 

 current for two houi-s, when they are changed for others 

 fully charged, the changing being effected in a very simple 

 way. A trolley with four series of rollers is brought oppo- 

 site the end of the car, the two trays of exhausted cells are 

 run out on to two series of rollers on the trolley, a winch 

 is turned, the other two series of rollers carrying the fresh 

 cells are brought opposite the openings in the car, and the 

 trays then run in, the whole work of changing being 

 accomplished in almost as little time as would be taken in 

 changing horses. 



The car is placed on small " bogie " frames, whereby 

 the weight is so distributed as to permit of the ordinary 

 light roads bt-ing retained in their present condition, while 

 they also increase considerably the comfort of the pas- 

 sengers, more especially when turning sharp curves. 



Electric bells are fitted so that each passenger, without 

 leaving his seat, may signal to the driver to " stop ; " while 

 from the roof hang a number of electric lamps, the fila- 

 ments of which are, when required, rendered incandescent 

 by electricity derived from the cells under the soat. 



There remains now but one question — that of cost. It 

 has been the impression of most people that there were so 

 many and such extensive sources of waste in the conversion 

 of steam power into electric power, as applied by secondary 

 cells, that their adoption would therefore be precluded. But 

 Mr. Reckenzaun maintains that he gets on the axle of his 

 car 33 per cent, of the power of his steam-engine. Locomo- 

 tive steam-engines are always costly, and those used on 

 tramways are no exception to the rule, as they consume 

 three to four times as much fuel per horse power as would 

 be required by a large stationary-engine, such as would be 

 used for charging the secondary cells ; wherce it is clear 

 that the balance is considerably in favour of electricity. It 

 is to be noticed, further, tiiat while the piime cost of an 

 electrical equipment is very much less than for steam driven 

 cars, the co-st of maintenance is much lower, there beins 

 also fewer sources of depreciation, the chief of which are 

 in the cells. The negative plates maintain their efliciency, 

 but the positive plates gradually become peroxidized, and 

 require renewing. Lead, however, is cheap, and the 

 renewal is very easily effected. 



It is stated that the running cost, including 15 per 

 cent, depreciation on machinery, and 50 per cent, on the 

 seconda-y cells (percentages which will proVjaVily present a 



good margin on the right side) amounts to 3^d. per car 

 mile, as compared with about 7d. for horse power. 



The new system has already obt:iined the approval of 

 Gen. Hutchinson, (roni the Be ard of Trade, and there is 

 every pros-ptct of its speedily being bronght into public 

 use : to Soon, that is, as the local autlioriliea can 

 be induced to give the sanction necessary. It only 

 remains to say tliat on the occasion of a visit which I 

 made recently to Millwall, I was thoioughty convinced of 

 the practicability of tbe system £0 far as the power to do 

 the work was concerned, and it is safe to presume that the 

 calculations which have been made as to cost have been 

 taken on good grounds, and are well within the margin ; at 

 least, 1 hope so. 



NEEDED STAR-SURVEYS. 



By Bicuard A. Froctou. 



( Continued from p. 42.) 



SUPPOSE we could pay a visit to the midst of the 

 Pleiades. What should we find 1 According to 

 ordinary ideas we should find simply a number of suns, 

 each, like our own, the centre of a system of worlds. Yet 

 it is demonstrable — and easily — that we should see around 

 us something entirely unlike the star-strewn heavens that 

 we now see. Probably most of the stars now visible to u; 

 would still be in sight, and scattered with much the same 

 relation between the lustre and average apparent distance 

 as in our jnesent skies. But how about those stars which 

 belong to the group we are visiting 1 With what lustrr 

 would the six stars shine which ordinary eyesight recog- 

 nises in the Pleiades, or the fourteen stars which some 

 keen eyes can discern in the groui) ? It is certain, from 

 the apparent size of the group, that the entire space of thf 

 Pleiades cannot be more than the fiftieth part of the dis- 

 tance separating the Pleiades from us. Therefore set in 

 the middle of that group we should be within les.s than one 

 hundredth of our piesent distance from all the stars of the 

 group. Alcyone now shines as a third magnitude star, 

 five others of the gioup as stars of the fourth magnitude. 

 How would they appear if we diminished our distacce to 

 one hundredth part of its present amount 1 Their lustre 

 would be increased, not a hundredfold, but one hundred times 

 a hundredfold, or ten thousand times at least. Many of 

 them would be far more greatly increased in brightness. 

 They would no longer be stars, but suns, ju.st as Sirius in 

 the great reflector of Lord Kosse, though still but a mere 

 point in apparent size, shines like a young sun. The scene 

 presented by the hundred stars of the Pleiades would be 

 indescribably beautiful. In the Vjackground would lie a 

 star scene as beautiful as the heavens we now see ; but it 

 would be scarce noticeable amid the splendour of a hundred 

 suns, the least outshining Sirius a hundredfold in splendour. 

 And among these, the greater glories of the night skies 

 within the Pleiades there would be varieties in glory as 

 great as among the stars of our own skies ; for the stars 

 which sef.m. so unequal in the Pleiades are really &% unequal 

 as they seem, since the whole group must be regardeel as 

 practically at the same distance from our earth. 



But this is nothing compared with what we should find 

 if we could visit some of those glorious clusters which have 

 been ]ioetically de.scribed by Tennyson as " bee-like swarms 

 of suns." The idea that the stars of those clusters are dis- 

 tributed like the suns of our firmament, that we have 

 merely to count their number and say there are so many 

 suns each girt round by its family of worlds, and each 

 leppatirg not only the glory of our own sun but all tlie 



