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after the Plan of the Marr Construction Company.
But the voltaic light was too brilliant for a small area. How to divide and subdue it so as to render it suitable for house lighting, was still a difficult problem. Farmer, Sawyer, Mann, and Edison, all attacked it at nearly the same time, going back with singular accord from the voltaic arc principle to that of incandescence in a vacuum. Edison, the prodigy of the century in inventive genius, was the most successful. Besides improving the dynamo, he perfected with little difficulty a cheap vacuum-globe. 1878] THE MARCH OF INDUSTRY 347 After long experimenting he succeeded in the more arduous task of securing an automatic checking of the current before it became hot enough to consume the incandescent carbon. 
Edison's Platinum Lamp on Carbon Support, 1879. Edison's Paper Carbon Lamp.
348 THE CEMENTED UNION [1878 The alarm was premature, however, since the new illumination did not, after all, prove so satisfactory as to displace the old. It largely did so for streets, factories, and halls, but to no very great extent for residences. 
Edison's First Incandescent Platinum Lamp. The most stupendous engineering work yet accomplished by man, the great bridge spanning East River between Brooklyn and New York, was completed in May, 1883, excavations for its foundations having begun so early as 1870. This wonder of the world was designed by John A. Roebling, and after his death in 1869 finished by his son, W. A. Roebling. 1883] THE MARCH OF INDUSTRY 349 It cost about $16,000,000, two-thirds coming from the city of Brooklyn, one-third from New York. A gigantic stone tower, 277 feet high, was built on each side of the river. Through arched apertures in these toward the top ran the roadway, its ends being 119 feet above the water. The centre of the bridge was supported by four steel wire cables, 16 inches in diameter, which passed from solid masonry structures nearly 1,000 feet away from the water's edge on either shore, up over the two towers, dipping, at the centre of the river, to nearly the level of the roadway. On account of their great weight they had to be braided, strand by strand, in their permanent position. Suspenders from these cables grappled the body of the bridge at frequent intervals. The main span was I,595-1/2 feet long, the entire work about 6,000 feet. There were five passageways--two on the outside for carriages, the next two for cable cars, the middle one for foot passengers. The bridge curved upward from each tower, being at the middle 135 feet above the water in summer, and three feet higher in winter, owing to contraction by the cold. All but the very largest ships sailed under without shortening their masts. 350 THE CEMENTED UNION [1883 In connection with the great bridge, as likewise in a way possessing an importance for the whole nation, we may mention the ingenious deepening of Hell-gate Channel, East River, by tunnelling beneath the water and using dynamite; and also the introduction of elevated railways in New York City and Brooklyn. This project had been mooted by 1868. Exactly ten years later two sections of railway were open for travel in New York. The first elevated road in Brooklyn began operation in 1885. These new avenues of travel at once became immensely popular. In 1884, no fewer than 250 engines and 800 cars were in use by the New York lines, carrying over 300,000 passengers daily, or about 103,000,000 for the year. Nearly at the same time with the introduction of these roads in New York, new methods of traction for surface street railways, by electricity and by cable, were introduced in various cities of the country, bidding fair soon to do away with horses for this service. 351 
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