ENGINEERING. 



283 



forced by 40 feet of masonry. The total cost 

 is estimated at $6,000,000. 



A railroad-bridge has been erected across the 

 Kinzua Valley, in Pennsylvania, for the New- 

 York, Lake Erie, and Western road, which is 

 the loftiest structure of the kind in the world, 

 and so light that it appears as if made of wire. 

 The highest pier is 297 feet in height, the av- 

 erage height being 176 feet. It crosses the 

 Kinzua Creek at an elevation of 2,100 feet 

 above the sea. Engineers have for several 

 years studied the best way to cross this deep 

 ravine, which lies in the way of a railroad be- 

 tween Pittsburg and Buffalo. The gigantic 

 viaduct which has been constructed was planned 

 by O. W. Barnes. Its length is 2,051 feet from 

 abutment to abutment. The height of the rail- 

 level above the bed of the small stream in the 

 center of this chasm is 301 feet. There are twen- 

 ty spans of 61, and one of 62 feet. The width 

 of each tower is 38 feet at top. The truss is 6 

 feet high and 10 wide. It is continuous. The 

 braced columns which form the piers are one 

 foot in diameter. They incline with a batter 

 of two inches in a foot. Each column rests 

 on a base of masonry. The iron shoes to 

 which the columns are fastened are imbed- 

 ded in the copings of the piers, and each one 

 is anchored by two large bolts passing through 

 the pier and fastened to iron plates at the 

 bottom. These bolts are designed to add to 

 the security against wind strains. Four mil- 

 lion pounds of iron and seven thousand cubic 

 yards of masonry were used in the construc- 

 tion of the viaduct. The foundations are most- 

 ly in solid rock, but for a few piers near the 

 bottom they are on piles. 



The new bridge designed by the English en 

 gineers, Fowler and Baker, to cross the Forth, 

 which will be the widest-span bridge in the 

 world, is of a new type, and will be the first 

 bridge built of steel. The principle of the de- 

 sign is to have enormous balanced cantalevers 

 on two river-piers, and the space between them 

 in the middle span, bridged by a long lattice 

 girder, carried from the end of one cantalever 

 to the other. The steel employed will be test- 

 ed for a tensile strength of 30 to 33 tons to the 

 square inch, with 20 per cent elongation, and for 

 a resistance on compression of from 34 to 37 tons, 

 with 17 per cent elongation. There are two 

 spans bridged in the way described. The piers 

 holding the cantalevers are iron frames, resting 

 on foundations of rock and hard clay, each 350 

 feet high. The length of the central pier is 

 270 feet, that of the two others 150 feet. The 

 spans are each 1,700 feet. The balanced can- 

 talevers, or brackets, are about 675 feet long 

 each. They are fastened at top and bottom to 

 the iron frames of the piers. The two project- 

 ing brackets bridge about 1,350 feet of the 

 space between the piers. The remaining 350 

 feet are closed by a lattice girder, resting on 

 the tips of the cantalevers. The weight of each 

 bracket is about 3,360 tons. A suspension- 

 bridge over the Forth was commenced, but the 



work was abandoned when the Tay Bridge dis- 

 aster had awakened the minds of engineers to 

 the magnitude of the wind-strains which such 

 structures must undergo. The present design 

 was intended to attain exceptional strength and 

 rigidity, and to stand heavy freight and fast 

 passenger traffic, as well as the heaviest gales 

 which sweep the Scotch coast. 



The new Eddystone Light-house was set in 

 operation on May 18th. The tower was de- 

 signed by James N. Douglas, Chief -Engineer to 

 the Trinity Corporation, which has charge of 

 the British light-house system. It is as solidly 

 constructed as the old tower, and firmer than 

 if hewed out of a single block of granite, for the 

 separate stones are without a flaw, and are so 

 dovetailed together that it is impossible for any 

 of them to be displaced. Every one is fitted 

 into those above, below, and on each side, with 

 projections and grooves, and the interstices are 

 filled up with Portland cement. The curved 

 contour of the old light-house is also retained, 

 but with an important modification. Smeaton's 

 famous design, which allows the waves to roll 

 up the curved sides of the column, instead of 

 dividing the stress of the seas, concentrated 

 their force at the top of the tower, where they 

 exercised a powerful leverage upon the base. 

 The tower, with its interlocking blocks of 

 granite, was as strong, when recently taken 

 down, as when it was first erected, over a cen- 

 tury before; but the reef on which it was 

 founded, weakened by under- washing, had be- 

 come insecure. The new light-house is placed 

 on the southern rock, the middle one of the 

 three main reefs, 127 feet from the old one, 

 which stood on the western rock. The Eddy- 

 stone group of rocks occupies about a square 

 mile at low water. Their situation is nearly 

 midway between Start Point, in Devon, and 

 Lizard Point, in Corn wall, being about ten miles 

 nearer the latter. The rocks are of gneissic 

 formation. The new tower, instead of rising 

 in a parabolic curve from below the high-water 

 mark, is placed upon a cylindrical base of ma- 

 sonry 44 feet in diameter. The vertical sides 

 of this solid granite base rise 2 feet above 

 high water. From this cylindrical base the 

 curved shaft rises, leaving a terrace 4^ feet wide 

 all around. The granite blocks of which it is 

 built are some of them 6 feet deep and 2 feet 

 thick, with their outer curved face 3 feet 10 

 inches broad. The height of the focal plane of 

 the light in the old tower was 72 feet above 

 high water, while that in the new house is 133 

 feet, the former being visible 13 and the latter 

 17^ miles. 



The Tillamook light-house, placed by the 

 United States Light-house Board on the coast 

 of Oregon, eighteen miles south of the mouth 

 of the Columbia River, is invaluable for the 

 growing commerce of Portland and Astoria 

 with all parts of the world. The coast is lined 

 with precipitous basaltic cliffs. Tillamook Rock 

 is a reef rising 90 feet above the water a mile off 

 shore. The light is 136 feet above the sea. The 



