Track Inspector's Bicycle I N order to lighten the work of the plodding trackwalker a French inventor has designed an attacnment for a bicycle which will permit the machine to travel on the rails, thereby allowing the man who inspects the track and roadbed to cover a larger territory in a given time and with much less fatigue. The attachment is shown in the accompanying engravings. It consists of a pair of supplemental forks secured to the main forks of the front wheel md provided at their lower extremities with ollers adapted to bear on opposite sides of the rail. In additlrl to this thei"i is a light s:eel frame secured to the main bicycle at the rear which carries at its outer end a sma,1 roller that rides on the opposite rail of the track. This serves to keep the two wheels of the bicycle on the rail without any pffort of steering on the part of the rider. In or-iel to permit the rider to preserve a comfortable position when traveling slowly aronnd a curve Miafc is steeply banked, the roller is made adjustable under control of a small hand wheel, whereby it may he thrown in or out so that the rider can adjust himself as nearly as he desires to the perpendicular. The roller frame may be detached at a moment's notice and secured to the bicycle in the manner illustrated, and the supplementary forks may be raised, permitting the wheel to 1e ridden over an ordinary road. A Curious Indian Cantilever Bridge SO;E interesting examples of Indian ingenuity are afforded on the River Skeena and its tributaries in north British Columbia. These waterways in their upper reaches flow very swiftly and for the most part through deep ravines. As it is impossible for the Indians to cross them by means of canoes, they have resorted to bridging. Their bridges are interesting structures from the engineering point of view, inasmuch as the cantilever principle is adopted. The bridge of this design shown in the accompanying illustration spans the Bulkeley River where :t is about 120 feet wide, and the height from the bridge to water level is about W feet. I is built of wooden logs, the legs of the structure being formed of single stout logs varying from 60 to 80 feet in length. The task of lowering them into positi:m must have demanded COlsiderable ingenuity on the part of the builders. They are buried about 15 teet at their lower endi and anchored by the super- ini|iosiiion of masses of large rock rolled. and cal'rLed to the site. The longitudinal members of the shore spans are similarly buried in the ground and lashed to the ends, of the diagonal legs. These main members, corresponding to deck girders, are about 120 fe,3t in length, and to either end the A members of the superstructure are lashed. Elaborate cross braeing is resorted to in order to secure greater strength. When the bridge was first erected the different members were simply secured together by willow thongs, but when the British Columbian government erected a more substantial suspension bridge lower clown the' river, the Indians assembled and followed the white man's operations with great interest. They observed how the thick wire cablEs were slung and anchored, and accordingly d2cided to introduce wire into their own structure. They procured the material for tbis purpose from wherever they could and introduced it in a most fantastic manner. Also, when the Grand Trunk Pacific Railway 8ngineers commenced working on their track near by, the Indians procured odds and ends, such as bolts and spikes, from them for introduction in their bridge so that now it is a strang- looking pjece of work, though the fundamental cantilever lines are still distinct. A Giant Induction Coil T HE accompanying engraving illustrates one of the most powerful induction coils in existence, viz., a mammoth apparatus 125 oentimeters (49.2 inches) in spark length, constructed f6r the Vien n a Technical High School. A similar apparatus has been COl-structed for the Potsdam Astrophysical 0 b s e r v atory, both being warr;nted to stand a potential of 1,000,000 volts. The discharges of these induction coils comprise the • fundamental and upper harmonic vibrations, the minimum and maximum wave lengths being inferred approximately from the lengch of wire in the primary and secondary circuits respectively. In connection with the se giant induction coils the wave length of the fundamental vi b r a t i on s!s about 300 kilometers (186 mnes) and that of the highest upper harmonic about 100 meters (328 feet) . Their construction is based upon the folloWing voL ages between a positive point and negative plate with different distances at the moment of the first Elpark passage: Spark len)th (cms.)- 10 20 30 40 50 60 Voltage- 89 133 178 222 266 300 Spark length (cms.)-70 80 90 100 Voltage- 387 473 618 800 10nO On account of the special winding method contiguous terns of a coil will readily stand a much higher vo:tage so that their efficiEncy, owing to the much smaller self-induction, is i:1creased considerably, resulting in those wonderful remarkably sub s tant i a 1 discharges which sometimps show the aspect of flames. In fact, tbe diseharges vf these giant induction coils c ar r y a can s id erab 1 e amount of electricity.