806 



SCIENCE 



[N. S. Vol. XLI. No. 1065 



This paper gives a brief review of progress in 

 the development of marine electrical installations. 

 It emphasizes the importance of electric steering, 

 anchor windlass and other recent requirements. 

 The possibilities of under-water communication 

 are considered and improvements in searchlight 

 projectors recorded. The essential points in con- 

 nection with the introduction of electric propul- 

 sion and the opening field of possibilities not only 

 in the design of efficient electrical apparatus but 

 also in the effect upon the art of naval architec- 

 ture are concisely stated. 



The Nolachudkey Hydro-Electric Plant of the 

 Tennessee Eastern Electric Company: W. V. N. 



POWELSON. 



The Location and Maintenance of Bailroads and 

 Highways along Steep Slopes: Waltee Loeing 



The paper describes the development of a new 

 principle of construction, when it is necessary to 

 place the roadbed of a railroad or a highway 

 along a slope which already is so steep that any 

 increase in the rate of the slope, made by form- 

 ing the side slopes above or below the roadbed, 

 causes frequent slides. The usual practise has 

 been to construct retaining walls on the upper or 

 the lower side of the roadbed (or perhaps on both 

 sides) which are necessarily expensive, since they 

 must always sustain a great weight of earth. The 

 method described utilizes the skeleton construc- 

 tion permissible by reinforced concrete and re- 

 duces to a minimum the stresses which must be 

 sustained by the structure. An illustrated ex- 

 ample of the application of this principle, as de- 

 veloped by the writer in Oil City, Pa., is given in 

 detail. Another illustration of the same funda- 

 mental principle, as recently described in the 

 technical press, is also given. 



Construction of the New Double TracTc Tunnel of 

 the B. & 0. S. S. through Alleghany Mountains 

 at Sand Patch, Pennsylvania: Paul Didiee. 



Seconstruction of Bridge No. 100, Pittsburgh Di- 

 vision: J. O. Bland and John Millee. 

 This bridge, situated a little west of Coshocton, 

 O., was partially destroyed by flood in March, 

 1913, and the wrecked spans temporarily replaced 

 by girder spans. 



The structure, before the flood, consisted of 

 four double tracks through pin-connected truss 

 spans, each 152 ft. 2 in. o. to c. end pins, and was 

 replaced by three double track, through riveted 

 truss spans, each 240 ft. e. to c. end pins. The 



total shipped weight of the three spans was 2,740 

 tons. 



The old masonry was replaced by new concrete 

 piers and abutments, the foundations for these 

 being sunk by pneumatic caissons. This new 

 masonry was built by the Foundation Co., of New 

 York. 



The new bridge was erected on falsework on 

 the downstream side of the old, and when com- 

 pleted, was used as a run-around to carry trafSc 

 while the old structure was being dismantled. 

 The new spans were then rolled into position. 



Both the weight moved, 3,250 tons, and the dis- 

 tance moved through, 44 ft. 9 in., constitute a 

 record for an operation of this nature. 



The new steelwork was manufactured by the 

 American Bridge Co., of New York, and was 

 erected by the Seaboard Construction Co. 



The bridge was designed by Mr. J. C. Bland, 

 engineer of bridges, Penna. Lines West of Pitts- 

 burgh, under whose supervision the erection also 

 was carried out. 

 A Balanced Cantilever Bridge: Heney H. Quimbt. 



A bridge of a new type was recently constructed 

 at Chester, Pa. It consists of two independently 

 acting parts, each being a double cantilever of ten 

 longitudinal ribs of reinforced concrete resting on 

 a pier over which it is balanced with a counter- 

 weight, the channel ends of the cantilevers being 

 connected by a short so-called suspended span, and 

 the whole forming in appearance a concrete arch. 



The type was devised as the most economical 

 method of securing an ornamental arch bridge 

 which was desired at this point by the public au- 

 thorities for esthetic considerations, the subsur- 

 face conditions making a real arch very expensive. 

 These conditions consisted of deep soft mud on 

 one side of the river underlaid with a bed of rock 

 sloping steeply away from the channel to a consid- 

 erable distance and depth, affording no natural 

 skewback for an arch to thrust against. 



The pier on the deep mud side is on wooden 

 pile foundations with concrete capping, lateral 

 stability being obtained by surrounding the pier 

 with spur or batter piles. 



The bridge Is one hundred and sixty feet long 

 over all, with the main span ninety-five feet cen- 

 ters of piers, and the wings thirty-one and thirty- 

 four feet, respectively. It is sixty feet wide, with 

 cartway thirty-six feet between curbs. 



The action of the double cantilever is that of 

 the double overhanging gantry crane, the dead 

 load balanced with equal moments over the middle 



