Sidor som bilder

being formed by two circular arcs of sixty de- sonry in each anchorage, 13,000 perches; tctal grees each. The up-stream edge or nose of amount of masonry, 90,000 perches. Size of each main channel pier is sloped back at an towers at base, 86 by 52 feet; at top 74 by 40 angle of about thirty degrees from the perpen- feet. The wrought-iron floor beams (the length dicular, the better to enable them to resist, of two of which makes the width of the bridge) break up or turn aside masses of ice or other are each 19 feet long by 5 inches wide; and floating bodies. The pivot pier has guards, there will be two joined in every five feet of constructed of stone in the same manner as the bridge—one to each suspender. The weight itself, placed up and down stream at the proper is 20 pounds per foot. Two iron trusses 10 distances to receive the ends of the draw when feet high separate the foot road-ways, one on. swung open, and connected with the pivot pier each side, from the carriage-ways; and flat-iron by timber crib-work filled with loose stone. tracks, of accommodating width, are laid for

Superstructure. The superstructure, designed wheels to run upon. The wrought-iron girders, ultimately to be of iron, and to carry a double 30 feet long and 12 inches wide, will run the track, at present consists of a single-track tim- entire length, under the middle of the bridge. ber bridge, all except the draw spans being on The estimated total cost of this bridge is about the Howe plan.

$1,750,000. The trusses of the long spans are twenty-four The Connecticut River Bridge.—The Confeet high, and those of the short spans nine feet necticut River Bridge, erected on the line of high. The clear width between the trusses is the New Haven, Hartford, and Springfield Railfifteen feet.

road, where it crosses the Connecticut River, The draw, designed by Col. J. W. Adams, is has been replaced by an iron bridge on the the "arch brace plan,” the peculiarity of which same line as the old wooden structure, without consists in having the main supporting braces interrupting the traffic of the road. The diffiradiate from the ends of the lower chords to culty of this undertaking will be appreciated, different points in the length of the upper when it is considered that twenty-two regular chords, thereby transmitting the weight of the trains, and from two to four extra trains, pass bridge and load directly to the abutments. The over the bridge daily, and mostly during workends of the draw when swinging are supported ing hours. by eight chains composed of iron bars 5x1 The new bridge was designed and erected uninches, extending from the top of a central der the direction of James Laurie, Esq. The tower sixty feet high to the ends of the lower iron work was contracted for by William Fairchords of the trusses.

bairn & Co., and the London Engineering and The turn-table of the draw consists essen- Iron Ship-Building Company. tially of a series of seventy rollers, placed be The several spans were constructed from the tween two circular tracks, one being fastened plans by the above firms, put together with to the masonry of a pivot pier, and the other bolts, and every part fitted and adjusted before to the under side of the bridge. The faces of being shipped. The rivet-holes were all drilled the tracks, which are nine inches broad, are or punched, and such parts as could be permaaccurately planed, so as to present no obstacle nently put together without being too cumberto the movement of the rollers, which are some, were riveted by machinery. turned true and smooth. The rollers are twelve In arranging the spans of the new bridge all inches in diameter, and nine inches long on the the old piers and abutments were made use of, face. They are placed in the annular space be with the necessary alterations and additions to tween two concentric iron rings, and kept at bring them up to the proper height for the new the proper distance by radial bars, which con- girders. nect the inner ring with a collar fitted to and In the middle of each of the 177-feet spans revolving around a central pivot-pin six inches across the river, with the exception of the midin diameter.

dle or channel span, a new pier was built, like The Cincinnati Suspension Bridge.—This the old ones, so as to divide the seven river bridge was designed and built by John A. spans of the old bridge into twelve of 884 feet Roebling, Esq. The total length of this bridge, each, with one of 177 feet in the centre. including the approaches from Front Street, For convenience in building the new piers, a Cincinnati, and Second Street, Covington, is temporary track was laid inside the old bridge, 2,252 feet'; length of main span from centre supported by the lower chords, over which the to centre of the towers, 1,057 feet; length of stone for the lower part of the piers was hauled, each land suspension, 281 feet; width of bridge and lowered to its place. in the clear, 36 feet; its height above low water, The general form of girder is that of a truss 100 feet; height of towers from foundation, composed of rolled plate, angle and T iron. without turrets, 200 feet; height of turrets, 30 The posts or compression bars are vertical, and feet; number of cables, 2; diameter of cables, the ties or tension bars are at an angle of abont 124 inches ; strands in each cable, 7; wires in 45° with the chords, the several parts being all each strand, 740; wires in both cables, 10,360; firmly riveted together. weight of wire, 500 tons; deflection of cables, There are three distinct varieties of this gen88 feet; strength of structure, 16,800 tons; eral form adopted for the different lengths of masonry in each tower, 32,000 perches; ma spans, by which tbe use of bars beyond a cor

tain size is avoided in the longer spans, as The Susquehanna Bridge.—This bridge, de rolled bars of a inuch greater width than nine signed and executed under the direction of inches cannot be depended upon for such uni- George A. Parker, Esq., is situated nearly one form strength and tenacity as the smaller bars. mile above the mouth of the Susquehanna River,

The difference consists in the arrangement and four miles below the head of navigation and of the tie bars. In the channel span of 177 tide-water, and has been built by the Philadelfeet, the ties cross three of the panels formed pbia, Wilmington, and Baltimore Railroad Comby the vertical posts; in the 140 feet and 884. pany, at an expense of nearly $2,000,000. The feet spans they cross two panels, while in the engineering difficulties involved in building it 761 feet span they cross but one panel. were, principally, the unusual depth of water,

When the ties cross three panels diagonally, the unstable nature of the bottom at certain as in the channel span, the truss partakes some- points, and the more than common violence of what of the character of a lattice; and the the ice freshets peculiar to its locality. It is principle is capable of being extended still far- composed of thirteen spans, seven of 250 feet ther for longer spans by making the ties cross 9 inches each in the clear, east of the draw, four or more panels according to the length of and five of nearly the same dimensions, west the girder.

of the draw. The work of erecting the bridge was com The draw span is 175 feet long in the clear. menced the last week in June, 1865, and pro- The whole length of the superstructure of the gressed without interruption until the whole bridge, including the draw, from abutment to of the iron work was finished, on the 1st of abutment, is 3,273 feet 9 inches. Its height is February, 1866.

25 feet, and its width 22 feet 6 inches. Before commencing the iron work of the The 'piers are all of solid granite masonry, several trusses, a series of blocks were laid sheathed from the bottom to the height of exacross longitudinal timbers placed under the treme high water (eleven feet above ordinary position to be occupied by each girder, for the high water) with plate iron. The masonry purpose of supporting it during construction. above water is cut to joints of one-eighth of an These blocks were of the proper height to give inch, and where exposed to lateral pressure is the required camber to the girders, and were clamped in the courses vertically and horizonplaced under each post. Upon these were first tally. At the top of the sheathing the piers placed the plates of the lower chord, which are eight feet wide, and their sides batter to were then riveted together in their proper the bottom at the rate of five-eighths of an inch places. Next, the posts were placed in posi- to the vertical foot. They terminate at each tion and riveted to the plates of the lower end in triangular starlings seven feet long on chord. The top chord was then put on, first the top, wbich have a double sheathing of the side prates and angle irons, then the hori. wrought iron. They do not project like the zontal plates and covers. After the plates were ordinary ploughshare-shaped ice-breakers of all riveted, the camber blocks upon which the American bridges, but have a concave outline girders were built were removed by striking at their salient edge; not being exposed to the the wedges upon which they rested, leaving the momentum of the ice-fields moving down long girders supported by the ends.

planes, this modification of the ordinary form During the construction of the bridge, as seemed necessary; as these piers have only to soon as any part was finished and the track meet, when subjected to their greatest strain, a placed upon it, heavy trains, weighing about steady crushing pressure, resistance to which one ton to the foot, were run over it to test its cannot be much aided by any mechanical consafety. These loads were not so heavy as it trivance, but which must be met in the main was designed ultimately to subject the bridge by simple inertia and irrefragibility. An uncomto as a test, on account of the rest of the bridge, mon degree of inertia (proportioned to bulk) is where the iron work was not completed, not given to these structures by their iror sheathbeing in a condition to bear the extra strain. ing, and also by the extraordinary density of

The channel span, however, was subjected to the stone of which they are composed; the a severe test by loading it with railroad bars, latter being Port Deposit granite, weighing in addition to a heavy train of four cars loaded more than one hundred and sixty-five pounds with iron, with the engine and tender; in all, to the cubic foot. They are 35 feet 4 inches about 220 tons. This would be about 13 tons long, and 7 feet 4 inches wide at the bridgo to the foot. With this load the deflection of seat. The draw pier is circular, 24 feet 8 inches the girders was 16' on one side, and on in diameter at the top of the iron sheathing. the other. When the load was removed there The abutments are of solid masonry of the was a permanent deflection of only it" on one same character as that of the piers, but not iron side and none on the other.

cased below the water line. Above high-water The cost of the iron, delivered in New York, line they are hollow, and contain offices and apwas $241.55 per ton, in United States curren- pliances necessary for the uses of the bridge cy, $117.18 of which was premium paid upon and the railroad. Their upper story is of iron, gold. The total cost of on work of the corresponding in architectural character with bridge erected and completed was $277.41 per the covering of the superstructure, which they ton, or 12 30% centi per pound.


[ocr errors]

6 6

FIG. 2.

The easterly abutment and the six easterly sixty piles per day. At one of the piers where piers rest upon pile foundations. The western the water was thirty-nine feet above the foundaabutment, and all the other piers, rest upon tion piles, a construction wharf was built around solid rock. The eastern abutment was built the site in the manner shown in the accompawithin an old embankment of earth where the nying drawing. The caisson of this pier was water stood at about the level of the foundation piles; and the abutment on the western

st shore was built in water seventeen feet deep. The depth of water at the several piers is as follows: at pier one, 21 feet 2 inches, and successively 19 feet 2 inches, 38 feet 5 inches, 7 feet 5 inches, 9 feet 10 inches, 31 feet 6 inches, 30 feet 8 inches, 31 feet 4 inches, 25 feet, 22 feet, 17 feet 6 inches, and 11 feet.

Coffer-dams could not have been used upon the foundations of this bridge with any chance of success, except where the water is shallow, or rather where it is of ordinary depth, for it is nowhere of much less depth than the St. Lawrence, where it is the deepest at the site of the Victoria Bridge; nor could pneumatic piles have been used here but in exceptional cases. It would have been hazardous in the extreme also to have attempted to use the method adopted by Mr. Brunel at the Salrash Bridge. The

ruder and more unscientific methods, dependent more or less upon chance for their effi- fastened to a timber platform, four feet thick. cacy, which are sometimes resorted to by engi- The platform was made to move vertically neers in difficult situations, were altogether within guides attached to these constructed unavailable here, for various reasons. The

wharves. Three arms projected from each sido means actually employed, therefore, for effect of the platform. Screws of three and a half ing the under-water work were 'necessarily inches in diameter and fifty-six feet long, sesomewhat different from the ordinary, and cured to simple turning-gear erected upon the consisted mainly in the use of portable iron deck of the wharves, were passed vertically caissons

sunk upon prepared foundations, partly through nuts contained in these arms. Upon by the use of screws, and partly by means of the screws turning horizontally, and having no guide piles only. Where the foundations were

other movements, the pier was made to deof piles, these were driven as far as was possible scend, or, if required by any exigency, to move with a ram weighing 2,200 pounds, and were

in the opposite direction. This movement is sawed off at a level as 'much below the river excellently well illustrated by the elevators bed as was practicable. The sawing was ef- used at hotels. The caisson was designed to fected by a very simple machine, which accu

be water-tight. The boiler-plate iron used was rately did its work in depths of water exceed three-eighths of an inch thick from the bottom ing forty-two feet, at the rate sometimes of to within ten feet of the surface of the water,

and elsewhere one-quarter of an inch thick.

It was made rigid by angle iron atMODE OF SINKING PIERS AT SUSQUEHANNA BRIDGE.

tached to the sides and ends in rows about seven feet apart. During the process of lowering, it was heavily braced inside with oak timber, to strengthen it against the pressure of the water outside, which at some points in the descent was sixteen pounds to the square inch.

The superstructure of this bridge has some peculiarities. It was originally designed to be of iron, but when the time came for its erection that material could not be procured of the requisite quality with that promptness which the emergency required, and, though with great reluctance on the part of tho engineer, timber was employed as a substitute. The chords of the trusses vary in their dimen

[ocr errors]
[ocr errors]

sions to suit the strains imposed upon them. on account of the situation. The upper sur. This variation is made necessary by the great face of the bottom chord and the lower sur length of the span, which could not be reduced face of the top chord are curved therefore, in

[ocr errors][merged small][ocr errors][ocr errors][merged small][merged small][graphic][ocr errors][merged small][merged small][merged small][merged small][graphic][subsumed][ocr errors][ocr errors][ocr errors]

BRITISH NORTH AMERICA, comprising than the pressure of the United States internal Canada, Nova Scotia, New Brunswick, New- revenue tax: Grain, flour, and breadstuffs of foundland, and Prince Edward Island. His Ex- all kinds; animals of all kinds; fresh, salted, and cellency Right Hon. Charles Stanley, Viscount smoked meats ; cotton, wool, seeds, and vegeMonck, Governor-General of British North tables; undried fruits, dried fruits; poultry, America, and Captain-General and Governor- eggs; stone or marble, slate; butter, cheese, in-chief in and over the Provinces of Canada, tallow, lard; timber and lumber of all kinds; Nova Scotia, New Brunswick, and the Island of pelts and wool; dyestuffs; flax, hemp, and tow; Prince Edward, and Vice-Admiral of the same, unmanufactured tobacco; woollen rags; bụrr etc. Denis Godley, Governor-General's Secre- and grind stones, wrought. tary; Lieut.-Col. Hon. Richard Monck, Military There were three other points embraced in Secretary ; Capt. Pemberton, 60th Rifles, aide- the proposition from the House committee. de-camp; Lieut.-Col. Irvine, Provincial aide-de- First, the mutual use of the waters of Lake camp; Lieut.-Col. Bernard and Lieut.-Col. F. Michigan and the St. Lawrence. Second, the Cumberland, Extra Provincial aides-de-camp. free transit of goods under bond between the The Canadian Cabinet.—Sir N. F. Belleau, Re.

two countries, and in that connection the aboceiver-General and Premier; Hon. A. J. Fergusson lition of the free ports existing in Canada. Blair, President of the Council; John A. Macdonald, Third, the concession of the right of fishing in Attorney-General for Upper Canada, and Minister of provincial waters. Militia; George E. Cartier, Attorney-General for Lower 'Canada; W. P. Howland, Açting Minister of delegates, stated their objections to the propo

The Hon. Mr. Galt, on behalf of the Colonial Thomas D'Arcy McGee, Minister of Agriculture and sition with frankness and ability. He thought Immigration; A. Campbell

, Commissioner of Crown that all the articles on the free list of the reci. Chapais, Minister of Public Works; James Cock: procity treaty, and such others as might be burn, Solicitor-General for Upper Canada ; Hector agreed on, should be dealt with on the basis of E. Langevin, Solicitor-General for Lower Canada. imposing custom duties as heavy as the internal

Nova Scotia.--His Excellency Lieutenant-General taxes of the United States. With reference to
Sir William Frederick Williams, of Kars, Baronet, the fisheries and navigation, he took the ground
K. C. B., Lieutenant-Governor.
New Brunswick.—His Excellency Major-General the transit trade, he agreed that it would be

that no new arrangements were required. As to Charles Hastings Doyle, Administrator.

Newfoundland. His Excellency George Dundas, desirable that the regulations for passing goods
Esg., Lieutenant-Governor.

under bonds should be reduced to the form of a Prince Edward Island. His Excellency Anthony law, and there seemed to be no reason why a Musgrave, Esq., Lieutenant-Governor.

uniform system should not be adopted. With The Reciprocity Treaty between Canada and reference to the assimilation of duties between the United States.—This was the subject of a the two countries, he said that it would be the conference between a delegation from the Colo- desire of the Colonial delegates to unite with nial Government of Canada and the Committee the committee in making the duties upon of Ways and Means of the United States House spirits, beer, tobacco, and cognate articles afof Representatives, in January, 1866. The in- fected by the excise duties upon them, such as terviews took place at the Treasury Depart- might be determined to be the best revenue ment, Washington, with the approval of Hon. standard. As to other articles, the Colonial Mr. McCulloch, Secretary of the Treasury. The Government was disposed to make mutual arColonial delegates were the Hon. Messrs. Galt rangements on a satisfactory footing. Mr. Galt and Howland (Canada); Henry (Nova Scotia); expressed the hope that the time would come and Smith (New Brunswick); and the Congres- when the policy of the United States would not sional committee, Messrs. Morrill, of Vermont; be as restrictive as now. With regard to the Hooper, of Massachusetts; Brooks, of New navigation of the internal waters, it would seem York; Garfield, of Ohio; Wentworth, of Illinois; to be advantageous to both sides to have the Conkling, of New York; Moorhead, of Penn- trade free. He also expressed the willingness sylvania ; Allison, of Iowa, and Hogan, of Mis- of the Canadian authorities to assimilate their souri.

patent laws to those of the United States. After a general discussion upon the subject On the 6th of February, all the questions inof reciprocal trade, Mr. Morrill submitted, on volved having been discussed at numerous sitbehalf of the committee, the following list of tings, the Colonial delegates rejected the Amerarticles which he thought should be admitted to ican proposition as a whole, and expressed a the United States with no higher duty than the feeling of disappointment at the unsuccessful pressure of the United States internal revenue termination of the conference. Mr. Galt stated tax: Fish of all kinds; products of fish; hides, that the Canadian Government were prepared to furs, skins, and tails, undressed; horns, ma- let the present trading facilities continue withnures; pitch, tar, turpentine; ashes; coal, fire- out asking for any further security from the wood; plants, shrubs, and trees; fish-oil; rice, United States, or giving any assurances on the bark; gypsum, unground; burr and grind stones, part of Canada. The question of the fisheries unwrought; rags, except woollen, unwrought. they would leave, as it would be left at the termi

The articles mentioned below he thought nation of the treaty, to be dealt with by the seve should be made to bear a higher import duty eral Legislatures of the United States on the one

[ocr errors][ocr errors]
« FöregåendeFortsätt »