690 



SCIENCE. 



[N. S. Vol. XII. No. .SOS. 



it Is au 'undulating railway,' its stations are 

 all set on the crest of gradients rising from 

 either side, illustrating the plan proposed in 

 Robert Stephenson's day by Badnall with the 

 published approval of that great engineer.* 

 This arrangement is perfectly feasible whereas 

 here, the stops are all made at precisely the 

 same points and with practically similar inter- 

 mediate speed of trains. It insures gain in 

 operation by the utilization of the stored energy 

 of the train at a stop, instead of its waste by 

 the use of the brake. Leaving the station, the 

 descent is utilized in securing the required ac- 

 celeration, thus again saving power. The 

 gradients are 1.66 to 2.33 per cent., and the 

 latter is equivalent to 74 pounds per ton on the 

 drawbar. One hundred horse-power minutes 

 are thus gained at each stop and at each start. 

 The electric locomotives were supplied by the 

 General Electric Co., the converters by the 

 Thompson-Houston Co., the electric 'lifts' at 

 the stations, dropping the passenger 60 to 90 

 feet at the start and raising him to the surface at 

 his destination, were furnished by the Sprague 

 Electric Co. The tunnel is double-barreled, 

 each tube being 11 feet 6 inches in diameter. 

 There are 13 stations and the running speed 

 ranges from 14 to a maximum of 25 miles an 

 hour between stations. Twenty- eight locomo- 

 tives are employed; each hauling a train of 

 seven cari-iages, conveying at most 336 passen- 

 gers, the train weighing, empty, 105 tons, ex- 

 clusive of the locomotive. The latter weighs 

 about 50 short tons. Power is supplied also by 

 an American firm, the E. P. Allis Co., who 

 furnish sis cross-compound engines, designed 

 by Reynolds, of 1,300 to 1,900 horse-power 

 each, and these are supplied with steam by 16 

 Babcock & Wilcox water- tube boilers — another 

 American invention. The generators are three- 

 phase, alternating current, with revolving fields. 

 The armatures weigh 48,000 pounds. The out- 

 put is 850 kilowatts, each, at 5,000 volts, 25 

 periods per second. Four six-pole exciters, 

 driven, each, by a compound engine at 450 r. 

 p. m. , direct, supply to each generator 50 kilo- 

 watts at 125 volts. The switchboard is of mar- 

 ble. There are 19 miles of cable, weighing 78.4 



* Treatise on ' Railway Improvements,' by R. Bad- 

 nall ; Loudon, Sherwood, Gilbert and Piper, 1833. 



tons. The engineers of the line are Messrs. 

 Benjamin Baker and Basil Mott. 



R. H. Thurston. 



WIRELESS TELEOBAPHY. 



Professor J. A. Fleming writes to the Lon- 

 don Times the following letter on recent ad- 

 vances in wireless telegraphy : 



As the subject of wireless telegraphy has not 

 yet apparently lost interest for the. general 

 reader, I venture to ask a little space to make 

 known for the first time some recent achieve- 

 ments by Mr. Marconi which have astonished 

 those who have been allowed to examine them. 

 Every one is aware that in his system of elec- 

 tric wave telegraphy an important feature is the 

 employment of an elevated conductor, which 

 generally takes the form of a wire suspended 

 from a mast. When Mr. Marconi attracted at- 

 tention by his feat of establishing communica- 

 tion across the Channel without wires, critics 

 raised a not altogether valid argument against 

 its commercial utility, that a wave or signal 

 sent out from one transmitter would affect 

 equally all receivers within its sphere of influ- 

 ence and hence the privacy of the communica- 

 tion would be destroyed. No one felt the force 

 of this objection more strongly than the dis- 

 tinguished inventor himself, whose original 

 work has caused so many others to attempt to 

 follow in his steps. For the last two years he 

 has not ceased to grapple with the problem of 

 isolating the lines of communication, and suc- 

 cess has now rewarded his skill and industry. 

 Technical details must be left to be described 

 by him later on, but meanwhile I may say that 

 he has modified his receiving and transmitting 

 appliances so that they will only respond to 

 each other when properly tuned to sympathy. 

 I am well aware that other inventors have 

 claimed to be able to do the same thing, but I 

 do not fear refutation in saying that no one has 

 given practical proof of possessing a solution 

 of this problem which for a moment can com- 

 pare with that Mr. Marconi is now in a position 

 to furnish. 



These experiments have been conducted be- 

 tween two stations 30 miles apart, one near 

 Poole in Dorset and the other near St. Cath- 

 arine's in the Isle of Wight. At the present 



