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The First Road Bridge over the Reversing Falls

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The First Road Bridge Across the Reversing Falls

Following is a paper by William Murdoch about the first road bridge across the Reversing Falls in Saint John, New Brunswick. It is from the Collections of the New Brunswick Historical Society, Vol. 4, No. 10, Saint John, N.B., 1919, pages 110-125.

The paper consists of several parts and is useful as a ready reference on the subject. The first part is William Murdoch’s essay which was written to accompany the other parts. It is pleasant reading. An important contribution of the essay is that it describes two earlier failed attempts to bridge the Falls. This is rare information and Murdoch was working from legend and hearsay even at the time. I am glad that he did!

The essay is followed by a three part inspection report of the completed bridge by engineer Alexander Light. The first part is the inspection report proper, and will likely be of more interest than the other two parts which itemize the strength of component parts and the details of tests. Alexander Light’s description is detailed enough that it would be possible to build an accurate model from it.

Finally, Murdoch presents a copy of an article from Harper’s Weekly telling the story of wind damage sustained in 1858.

The inspecting Engineer, Alexander Light, was an accomplished person. He had broad experience in bridge and railroad building and held important positions with several railroads, and colonial and provincial governments. He worked on projects in New York, Ontario, Quebec, the Maritimes, Newfoundland and elsewhere. His report about the Saint John bridge was written from Saint Andrews where he was, at that time, Chief Engineer of the Saint Andrews and Quebec Rail Road. Additional information about him can be found in the Dictionary of Canadian Biography Online.

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Following is the Murdoch paper:

The Saint John Suspension Bridge

William Murdoch, C.E.

In the original settlement of what is now the City of St. John, there were three separate colonies; one being that about the battery on the West Side on the mainland, near Navy Island, known in authentic history as Fort Frederick and claimed by some historian to have been the site of La Tour’s colony. The district was laid out as a town plot toward the end of the eighteenth century and called Carleton.

A town plot was planned for the eastern side of the mouth of the St. John River, bounded on the north by what is now Union street, and called Parrtown, John Parr having been at that time Governor of Nova Scotia, which then embraced the present Province of New Brunswick, and Sir Guy Carleton having been Commander-in-Chief of the British forces at the close of the American War of Independence.

The third district was that lying north of Union street and extending westward to the River St. John. A portion of this district, with the addition of Parrtown and Carleton, became consolidated into one corporation in the year 1785 and was styled the City of St. John. The remainder, extending northward to Kennebecasis River, was in the Parish of Portland.

In those early days the inhabitants found considerable difficulty in crossing the mouth of the river from one part of the city to the other, as the range of tide varies between twenty eight and seventeen feet according to the period of the moon. This, considered with the gorge about 500 feet in width at the head of the harbour, through which the tide delivers into the river at high water and flows out of the river at low tide, causes dangerous currents in the harbour, which were difficult to negotiate by the early oarsmen, and still are by their successors.

After all of the usual attempts to ferry the harbour by means of scows, etc., had produced a state of mind in the inhabitants which caused them to welcome any attempt to ameliorate their condition, a promoter proposed a bridge in extension of Watson street, West, to cross the river to Portland below the gorge. A charter was obtained in the year 1835 incorporating Benjamin L. Peters, Ralph M. Jarvis, Nehemiah Merritt, John Robertson, James Peters, Jr., James Hendricks, David Hatfield, Robert W. Crookshank, Robert Rankin, Robert F. Hazen, Edward L. Jarvis, Charles Simonds, Edward B. Chandler, William Crane, Hugh Johnston, Thomas Wyer, John W. Weldon and Jedediah Slason, as the St. John Bridge Company. The capital stock was set at £20,000 and increased by Act of the Legislature in the spring of 1837 to £28,000 and the work begun. A road was laid out, now known as Merritt street, to form the Portland approach, and a toll house built here. A timber pier was erected on the left side of the river and a primitive form of cantilever bridge begun. The land arm, which reached up to the toll house was, I understand, to serve as a counterpoise to the northern half span. As I am unaware of any records describing this structure nothing is left but to recall recollections imparted by old residents who had seen or heard of it, all of whom are now dead. In August of the year 1837, while undergoing erection, this fell, killing seven workmen and wounding others, the last of whom survived until about ten years ago.

Another bridge was attempted later on at the site of the present railway steel bridge at the falls, and it, too, fell, leaving the two communities still separated by the swift running waters of the River Saint John.

During this period a steam ferry boat was built and installed in the year 1840, to run from the western end of Princess street to Sand Point on the western, or Carleton side of the harbour until a terminus was built for it at the end of Rodney Wharf where it now is.

This boat, which was called the “Victoria,” was engined by Robert Foulis, a versatile Scotchman who had strayed here during the early years of the eighteenth century and of whom it seems well that, by way of digression, a few words might be given. He was a nephew of the brothers Robert and Andrew Foulis, of Glasgow, printers and publishers, whose productions were the admiration of all their contemporaries, and whose edition of “Horace,” published in the year 1714, was hung up, sheet by sheet, in Glasgow University and a reward offered for the discovery of a single error.

This scion of an intellectual breed was, I understand, a graduate of Glasgow University. After various experiences, when a young man, even to serving as surgeon in a whaling ship, he finally settled in the City of St. John and became a land surveyor, artist, analytical chemist and a civil and mechanical engineer. His survey of the River St. John is still in vogue in the Crown Land Office of this province; his microscopic portraits are exquisite works of art. His chemical knowledge ranged from analyzing ores to making his own whisky when overtaken by adversity. As an engineer he is said to have endeavored to promote a canal, upon the peninsula which contains Douglas Avenue, connecting the harbour of St. John with Marble Cove in order to make the river accessible at all times by means of locks. While operating as a mechanical engineer and owning a foundry he engined the ferry boat referred to, besides the first steam craft to ply the river to Fredericton and employed the late George Fleming, whose marine and locomotive engines, later on, became household words, and whose grandsons now operate the Phoenix Foundry. Mr. Fleming, when a young man, arrived in St. John from Scotland and was immediately engaged by Mr. Foulis. Later on when Mr. Foulis was the engineer of the light and signal service of the government of New Brunswick, his principal charge being Partridge Island whereon was an automatic fog bell operated by heavy clockwork supplied with pendulum and weights, he proposed a steam whistle instead of the bell, steam whistles being then new to the world. Later on his suggestion was acted upon; there was no patent law then and the inventor, though in his old age, blind and poor, was given no compensation, and the inventor of the fog horn died in poverty.

Now to return to our subject: William K. Reynolds, a native of New England and owner of a saw mill and timber limits at Lepreau, offered to erect a wooden suspension bridge across the gorge below the falls where the ground stands about one hundred feet above the tide at low water, the distance from cliff to cliff is fully six hundred feet and the width of water about five hundred feet.

A canvass was made among the citizens for the sale of stock in a company to build and operate the structure. An Act of Assembly was obtained in the year 1849 incorporating the Suspension Bridge Company, the only incorporator named in the Act being Mr. Reynolds. Sufficient stock was subscribed to justify a beginning and the work commenced in the year 1851.

Edward W. Serrell, a famous designer of suspension bridges, was engaged to prepare plans and supervise the work; and the promoter, William Kilby Reynolds, was employed to carry out the plans.

Mr. Serrell was an Englishman who had been bred, in his native country, to the trade of a cabinet maker, in which capacity he came to this continent and found employment in the United States. He took a deep interest in bridges, especially those of the suspension kind, of which he made models, and finally struck out as a bridge engineer, in which capacity he soon became famous and built the one which spans Niagara river at Lewistown, then the longest in the world, being 1040 feet.

A word about suspension bridges: The principle is of ancient origin and has long been in vogue among primitive peoples, even among the apes, a branch of the animal kingdom that humans do not associate with. They are said to have the habit of linking their bodies one to another, each grasping the tail of the other, and suspending this living chain from a tall tree overhanging the cliff of an inaccessible gorge, then swinging themselves to and fro, as a pendulum, increasing the momentum, until the opposite side is reached when the duty of the endman in this case is to attach himself to some object and thus form a bridge on which the migrants cross the ravine. Primitive suspension bridges have consisted of two ropes thrown from cliff to cliff and a floor secured thereto, the ropes being well tightened and a roadway thus obtained. Such viaducts have long been used in Peru and in Thibet.

The modern suspension bridge consists of this principle, the points of suspension being elevated to such a height that a floor can be hung from the chains or ropes to the level of the roadway. The British and European general practice was to hang such a deck from chains and the American to use wire ropes, a pronounced example of the former being that over Menai Strait, in Wales, and of the latter type, the first Brooklyn bridge in New York.

The Welsh bridge was a pioneer structure of the kind and, for a long time, looked upon as one of the wonders of the world. It connects Carnarvonshire with the Island of Anglesey, where the strait has a width of about nine hundred feet. The suspension span of iron measures 579 feet, 10 inches, from centre to centre of towers, with a clear height of 102 feet above high water level. The Carnarvonshire approach consists of three spans of 52 feet, 6 inches each, and measures in all, inclusive of piers and embankment, about 400 feet; the Anglesey approach has four spans similar to those on the opposite end and a total length, including embankment and piers, of about 560 feet, thus giving an entire length of viaducts of about 1540 feet. It contains two roadways of 12 feet each in width and a footpath 4 feet wide between them. This work was begun in the year 1818 and completed in the year 1826 under the plans of Thomas Telford, who himself was as great a wonder as his famous bridge.

Thomas Telford’s home was that part of Scotland, bordering upon England, made classic by Sir Walter Scott. In the olden days it produced a kind of tourist, hated by the English for a reason given once by a gentleman of Northumbrian parentage who, when addressing Saint Andrew’s Society of this city, at an annual dinner, informed his hearers that although he had never heard of any of his ancestors’ remains being in Scotland, he had no doubt that a good many of the bones of his ancestors’ cattle reposed there.

In later years the Scottish border produced the poet James Hogg, known as the Ettrick Shepherd; Thomas Carlyle, the Sage of Chelsea, and the subject of this sketch who was the leading engineer of his day, and founder of the institution of Civil Engineers of which he was its first president, an office which he continued to hold for several years until his death.

He was born in Eskdale, Dumfrieshire, in the year 1757. When a child he assisted his father who was a shepherd. At fifteen he was apprenticed to a stone mason, and in his leisure studied Latin, French and German as well as English; then he essayed to be a poet, writing a number of effusions over the nom de plume of “Eskdale Tarn,” but his real measure was found when employed in Edinburg at the erection of houses in the “new town.” Here he turned his attention, when twenty three years of age, to architectural drawing, and two years later we find him in London, where he was employed in the erection of Somerset House. In 1784 he superintended the building of a house for the Commissioner of Portsmouth Dockyard and repaired the castle of the member of Shrewsbury, Sir W. Pultenay. This gentleman, realizing the attainments of the clever young Scotchman, secured his appointment to the office of Surveyor of Public Works for the County of Salop; when the most brilliant of careers opened up before him, although he was thirty-five years of age when he built his first bridge. He designed and supervised the construction of a number of canals in Great Britain and Sweden, roads in various parts of Europe and Britain, including 920 miles through the Highlands of Scotland, where he built no fewer than 1100 bridges, and similar work in the mountains of Wales, thus giving the name which still attaches to the class of roads known as “Telford.” His principal docks were in Pultenaytown, Aberdeen, Dundee, London and Glasgow, and the year before his death he reported on the water supply of London.

It was in the course of his work in Wales that he designed the Menai and Conway suspension bridges on the line of a new road to Ireland, and he was consulted on this continent when the attempt was made to promote the Bay Verte Canal. He died at the age of seventy seven years and was buried in Westminster Abbey in September, 1834.

The East River suspension bridge was designed by John A. Roebling, civil engineer, of New York, and completed by his son, Col. W. A. Roebling. It consists of three spans, the main one being 15951/2 feet and the side spans 930 feet each, making a total length of 34551/2 feet. The approaches measure 25331/2 feet, giving a grand total of 5989 feet, or one mile and 709 feet. The height of roadway above high tide is 135 feet; towers are 272 feet and the breadth of bridge is 85 feet.

Each wire of the bridge was dipped repeatedly in oil which was allowed to harden between the dippings until each wire had a moderately thick coat of hardened grease to prevent oxidation. Each of the four cables contains 5700 wires thus treated, the wires running longitudinally and securely wrapped on the outside, the diameter of each cable being fifteen and one half inches. The strength of these steel wires is rated at 160,000 pounds per square inch.

The senior Roebling also constructed the combined railway and passenger bridge at Niagara Falls, on the suspension plan and, in doing so, exercised his ingenuity in overcoming elasticity which is the objection to such for railway purposes.

Its length is 821 feet, 4 inches and the cross-section consists of a four sided box 18 feet deep with a lower floor 24 feet wide, for team travel, and a top for railway travel and foot passengers with a total width of 25 feet. The walls of this box are lattice girders securely fastened, with the object of obtaining rigidity under a rolling load. It is suspended from four cables of 3040 wires each and measuring ten inches diameter when wrapped. The ends of the cables in all such bridges are securely anchored into the ground that they may resist the strain imposed upon them, and the tops of the towers are furnished with iron saddles, placed on rollers that the cables may move without overturning the towers.

Returning to the St. John suspension bridge. The promoter pushed his work of construction in the years 1851 and 1852 but, as his franchise under the Act of 1849 terminated in April, 1852, and a finish could not be made on time, he obtained an extension until April 1, 1853, from the Legislature on April 7, 1852, and the work was performed as bargained.

Mr. Reynolds having undertaken with his subscribers that he would finance the entire operation alone until the bridge would be completed, and the Legislature having, in the session of 1850, voted a bonus of £2,000 to be distributed pro rata among the stockholders after completion of the bridge and a report from a competent engineer appointed by the Government certifying approval of the bridge and its approaches, very little risk was taken by the stockholders.

The Government appointed Alexander L. Light, a prominent and well known engineer of the time, to inspect the structure and the new roads leading to it. He reported as follows, viz:-

(From the “Courier,” May 28, 1853)

Report on the Saint John Suspension Bridge, to Hon. J. R. Partelow

Sir:- I beg to report to you for the information of His Excellency the Lieut.-Governor and the Government, that according to instructions received from you, bearing date the 21st January, I have carefully examined the St. John Suspension Bridge, erected under the authority and by virtue of the powers granted by an Act of the Legislature intitled “An Act to Incorporate the St. John Suspension Bridge.” And I hereby certify that the same is constructed in conformity with the requirements of such Act, and that (within the limits and conditions herein specified) it is of sufficient strength and quality in all respects to render it perfectly safe for life and property passing over the same.

The bridge is of the description generally called “Wire Suspension Bridge,” being composed of ten cables, five on each side, each cable containing three hundred strands of No. l0 wire, or three thousand in all. These cables pass over massive towers of masonry and are made fast to the solid rock behind by heavy anchors as will be hereafter described.

The span of bridge from centre to centre of points of suspension is six hundred and thirty (630) feet; width of roadway between parapet, twenty-three (23) feet; with a fifteen feet carriage way in the centre, and four feet each side for foot paths. The whole being suspended seventy feet above extreme high water mark.

I have examined all the component parts of the bridge, including the foundation, and have subjected the wires, suspending rods and floor timbers to a breaking strain, in order to form a safe calculation of the actual strength of the bridge, upon all which I beg to report in detail.

The towers upon the western side of the river are built upon two different kinds of rock, the northern part being built upon limestone, whilst the southern is erected upon a very hard dark colored trap rock. Between these rocks there is a decided fissure, which, I am informed, (for now that the tower is built I have no other means of knowing) did not extend under the northern tower, but ran out to nothing at the southeastern face of the same. This fissure, Mr. Reynolds, the contractor, tells me has been carefully cleaned out and rammed full of concrete and broken stone. On the edge of the fissure, where I had an opportunity of examining it, this is now nearly as hard as the rock itself.

This must be watched and kept carefully sealed up to prevent the water from getting in, which if allowed to enter, and to freeze, might do serious damage. So long as this is guarded against I consider the towers to be perfectly safe, as I am led to believe that all earth has been excavated from under them, they being built upon the solid rock, each of the different descriptions of which stands firmly upon its own base.

The towers upon the eastern side of the river are built upon a shaly slate rock. The northeastern tower has been regularly stepped down with steps cut at right angles to the horizon until it attains a firm footing at the bottom from whence it has been built up entirely of strong granite masonry, of a firm and durable character. The southern tower has likewise been cut down to a solid foundation; but whether from economical or other motives the base of the tower, which should be the strongest, having to carry the superincumbent weight of the whole, has been built of limestone rubble masonry, of not nearly the same strength as the masonry in the tower erected upon it, which is constructed of granite. This I consider a mistake, for though the work is safe and will last, I doubt not, for many years, yet it is not by any means of the same durable nature nor in keeping with the rest of the work.

To remedy this defect I would recommend the outside of this rubble work, where it is exposed to the weather, to be covered with a good coating of cement, made of the best hydraulic lime; and the outside of this to be weatherboarded. With due attention to this it may be made to last for an indefinite space of time.

The towers themselves are built of first-class granite masonry. They are fifty-one feet, nine inches high above the base, fifteen square at the bottom and six feet square at the top of tower below the coping. The coping stone that the saddle rests upon is seven feet square and one-half (1/2) feet thick. Each of the other courses is two feet thick. The stone at the outside of the towers is composed of, is grey granite of a fine grain and durable nature. The stones are dressed smooth upon the beds and builds, but the outside is rough, technically called with a quarry face with an arris or tooled margin one inch wide round the edge of each stone. The filling in the centre of the towers, I am informed, is composed of the best class limestone rubble laid in cement and grouted, each course being leveled off to correspond with the granite face before the next was laid. So far as I can judge from carefully examining the outside of the work it seems executed in a faithful and workmanlike manner. (For strength of tower see appendix).

On top of the towers rest the arrangements for compensating the contraction and expansion of the back stage. This consists of a lower plate of cast iron 3 x 4 feet square, bedded in the masonry and firmly fastened down with copper dowels to prevent any movement of itself. This plate is perfectly smooth on its upper surface. On it are inserted seven wrought iron cylindrical rollers; on these rollers a saddle is placed which consists of a plate of cast iron perfectly smooth on its lower surface to correspond with the upper surface of the lower plate.

The top of the plate is cut out into five grooves 8-1/4 inches apart from centre to centre, semicular and 3-1/2 inches diameter at bottom, and formed on a curve of 4 feet 6 inches radius in longitudinal direction of the bridge. In these grooves the cables rest. The effect of this arrangement is, that in the event of contraction or expansion of the cables from variations of temperature, the saddle moves along upon the rollers without wracking the masonry of the towers. I consider this an excellent plan and well adapted to answer the purpose intended.

The cable are ten in number, five on each side of the bridge, laid parallel to each other and composed of three hundred strands of No. 10 wire, about one-eighth inch in diameter of each cable, or 3000 strands in all. Before these cables were made the wire was boiled in linseed oil and franklinite, which prevents corrosion. I am informed there were six barrels of oil used in their preparation. These cables are hung over the top of the towers on each side in catenarian curves, the droop from the tops of the towers to the apex of the curve being about forty-five feet.

The cables on the land sides are carried back over the tops of the towers as nearly as possible on the same angle as on the bridge side of the tower. This causes the pressure on each side of the tower to be the same, the resultant of which is a vertical pressure. The cables are carried back on this angle until they meet the surface of the rock, where they are fastened by suitable arrangements of links and shackles of sufficient strength to anchors of wrought iron. These anchors are straight bars of best refined round iron four and one-quarter inches in diameter. There are two of them in each cable, the one set six feet behind the other, in holes drilled by machinery eight feet into the solid rock, at right angles to the tangent of the curvature of the back stays, and these secured by filling round them with iron wedges and lead. From the unfinished state of the anchor pits (the masonry proposed to be built over them not being yet commenced) the earth had washed in partially covering them, so that I could not examine them thoroughly. The parts exposed, however, were securely fastened. I would recommend that these anchors be housed over either with stone or brick arch or wooden house extending the whole length of the shackles, and the drainage from the same, which is not by any means perfect now, be made thoroughly complete.

Five of the cables on the western side of the bridge have been spliced. I do not anticipate any danger from this as it is made in what is technically called the return, after the cable has been passed around the frog of the anchor which is well and securely clamped; moreover from experiments that I have made on wire spliced in this manner, the wire broke at the perfect part and not at the splice. Suspension bridges in Europe are generally made of wires of promiscuous lengths, splicing them whenever the coil was run out. In the Friboargh Bridge, –  the largest bridge of the kind in Europe – the cables were made in this manner.

The suspension rods are three-eighth inch by six-eighth inch and are in different lengths to suit the curve of the cables. There are 147 on each side of the bridge, or 294 in all. They are suspended from the cables at every four feet, alternating regularly from one cable to the other beginning with the outside and going regularly on by steps of four feet at a time to the inside one, then beginning with the outside one again. These suspending rods have a stirrup at their lower extremities, into which the transverse beams of the roadway are fitted and are there nailed fast to prevent their slipping off. They are each of them provided with one or two turnbuckles according to their length. These are for the purpose of adjusting them by to bring them all into the same degree of tension. These suspension rods are amply strong enough, as will be shewn in the appendix, where the strength of the bridge and its individual parts are explained . . . . .   (Reference to four feet footpath on each side marked by longitudinal scantling each side of 15 feet carriageway, but paper mutilated so it cannot be copied verbatim).

The transverse beams of the road are three by fourteen inches in the middle, and three by twelve inches at the sides where they fit into the stirrups. This gives a slight curvation to the cross-section of the roadway and allows the water to run off the sides, where it passes through cast iron scuppers. The transverse beams are placed four feet apart from centre to centre.

The planking for the carriageway is placed longitudinally and rests upon the transverse beams. The planks composing it are three inches in thickness and from six inches to a foot and upwards in width, and from twenty to forty feet in length. On each side of the bridge above and below the transverse beams are the top and bottom chords of a section of eight inches by five inches and five inches by five inches. These are procured in long lengths of not less than thirty feet and spliced, bolted and banded together so as to make them equal to one continuous timber extending from one end of the bridge to the other. Iron bolts, three-quarter inch section, pass through these top and bottom chords, and through the intervening transverse beam at every crossing of the same. These chords have the effect of stiffening the bridge and distribute any passing load over three or four of the suspending rods.

The timbers of the handrail on the outside of the bridge are five inches by five inches. The posts are morticed into the upper chords and are braced with diagonal braces of a similar section, extending from the foot of one post to the head of another, forming a series of St. Andrews crosses. The tops of the posts are morticed into the handrail, the top of which is capped with a moulding extending one inch over each side of the same. The whole is trussed up tight by three-quarter inch bolts passing through the handrail and by the side of the vertical post and screwed up tight with a nut underneath the top chord.

The platform of the bridge has a slight curvature across the river of nine inches, the same being inverted to the curve of the chains. This curvature varies of course with the degree of temperature; in the extreme heat of summer the bridge will be nearly a level plane.

At either end of the bridge are six guys, three on one side and the same number on the other. These guys are small cables of wire one inch in diameter, extending from the rock on either side of the bridge, where they are fastened to the bridge itself, the guys upon one side pulling against the guys on the other in such a manner as greatly to neutralize the effects of the wind. These guys, however, are very imperfectly put in, being badly made, indifferently fastened and by no means in the proper state of tension. I would recommend these guys to be immediately attended to, and made as perfect as it is possible to make them, as I consider that there is more to be feared from the effects of the violent gusts of wind which sweep through the gorge than from almost any other disturbing cause.

The approaches to the bridge are only completed for about 150 feet on each side. The roads leading thereto are bad; on the eastern side there is a steep hill within 300 feet of the bridge, which should be cut down to a grade of 1 in 25, before heavy loads can be taken up it with any degree of facility. In fact – when the hill is covered with ice, as it was when I made the survey, it is almost impassable for loaded teams. The rest of this road passes through the Portland Town shipyards and is more or less blocked up with timber

From the end of the 150 feet approach at the western side of the bridge to the junction of the main road near the Asylum the road creeps round the base of sloping ground and is decidedly unsafe at any pace beyond a walk, when there is ice upon it.

The Act with regard to the road and approaches is indefinite as to how far they are to be completed. I estimate that it will require £200 to make a good road in keeping with the rest of the work from a point leaving the main road by the Asylum west of the bridge, to the same distance on the eastern side of the river.

The amount of work still remaining to be done to render the work perfect, and if which, if neglected, will considerably lessen the ultimate durability of the bridge, but which at the same time does not interfere with its being used for the present are: First, Repairing the spiral winding of the cables, technically called the sewing, where it has been broken in many places in taking them over the towers. If this is not done the water will get into these places and do serious mischief. Second, painting all the ironwork of the bridge a white color with white lead and oil. The white color materially weakens the action of the sun and allows any symptom of incipient oxidation immediately to manifest itself. Third, coating the limestone rubble masonry in the southeastern foundation with hydraulic cement and weather-boarding the same; likewise pointing the joints of the masonry in all the towers with cement. Fourth, finishing and refastening guys. Fifth, cleaning out, thoroughly draining and housing over anchors. Sixth, completing the roads to and from the bridge.

I have estimated that £500 is a sufficient amount to complete these items.

Speaking generally, with the exception of the above mentioned items, I consider the workmanship well executed and creditable to all concerned.

I cannot conclude this report without respectfully recommending that the wise intention of the Government with regard to it being periodically inspected should be carried out. Suspension bridges in particular require to be carefully watched, the stability of the whole depending in a great measure upon the perfection of its parts. It is no use if the cables are strong and equally strained if the suspending rods are not in adjustment, and vice versa.

In conclusion I would merely add that in the survey nothing has been taken for granted where there was the least possibility of applying a test; and where the least doubt could be entertained the fullest practical experiments have been made with a deep sense of the responsibility incurred

All of which is respectfully submitted by

Your obedient servant,

(Sgd.) Alexander L. Light.

St. Andrews, 25th February, 1853.

APPENDIX

On the Ultimate Strength of the Bridge and all its Component Parts

[Note: ‘Long tons’ are cited in this Appendix. One long ton equals 2,240 pounds, not 2,000 pounds – ed.]

The safe strength of the bridge I estimate to be 131 tons gross.

From the result of six experiments that I have made upon the strength of the wire used in the construction of the St. John Suspension Bridge, I found that hung in a catenarian curve at the same angle over the points of suspension and suspended over saddles struck to the same radius they broke with an average weight of 840 pounds net upon each wire. Now there are 3000 strands of wire in the ten cables: We therefore get 3000 X 840 = 2,520,000 lbs =1,125 tons, as the absolute strength of the cables

The suspended weight of the bridge I calculate to be 150 tons. This includes the weight of the cables themselves between the points of suspension, the suspending rods, floor timers, and all other suspended weight of the bridge. Deducting this 150 tons, the weight of the bridge, from the absolute tensile strength of the cables will leave 975 tons as the extraneous load theoretically that would cause fracture.

The best authorities upon construction, however, (vide Tredgold, Nicholson, Rennie) inform us that in order to be perfectly safe, either in wood or iron, we should never allow more than a quarter of the breaking strain as a safe load. My own practice has always agreed with this. Now dividing the 1,125 tons, the absolute strength of the cables, by 4 for a safe load we get 281 tons, and deducting from this 150 tons, the calculated weight of the bridge, we have 131 tons, as the safe load the bridge will sustain without a shadow of doubt, this being equally distributed all over the platform of the same.

I am informed that it was the intention that the bridge should bear a human being upon every two feet square. Now taking the average weight of man at 150 pounds net there should be 37-1/2 pounds upon every superficial foot, and there being 13,340 superficial feet in the platform of the bridge we have: 13,340 X 37-1/2 = 223 tons, as the load that this calculation would give. To arrive at this strength I believe one-third of the breaking strain was assumed as a safe load. Taking therefore as before 1,125 tons as the absolute strength of the cables, this, divided by three, leaves 375 tons; deduct from this 150 tons, the weight of bridge common to both calculations, we have 225 tons as the safe load according to this calculation, and my own experiments upon the strength of the wire. One-third of the breaking load may be safe, but a one-quarter I feel persuaded is more in accordance with general practice.

Though 225 tons, or even 131 tons, may seem a large load and more, probably, than ever will or should be allowed upon it, yet it is but fair to say that this is not by any means the greatest load that could possibly come upon it. The heaviest load that a bridge is liable to be subjected to, is estimated by various writers at 120 pounds per superficial foot. This is considering the bridge by some unforeseen circumstance to be crowded with people. This agrees with experiments of my own, as I have had no difficulty in crowding twenty persons averaging 150 lbs. each into twenty-five superficial feet. Mr. Brunel, in his report upon the Hungerford Suspension Bridge, says, “That a bridge should be able to support 120 pounds per superficial foot besides its own weight, and that no bridge can be called perfectly safe that will not do this.” Now taking as before the platform of the bridge as 13,340 superficial feet, and 120 pounds per foot as the greatest load that can by any possibility come upon it we have 13,340 X 120 lbs. = 1,600,800 pounds, or 714 tons, as the greatest extraneous load the bridge can be subjected to. We have previously shewn that 975 tons is the extraneous load that would cause fracture of the cables. Deducting 714 from 975 we have 201 tons excessive strength theoretically after the platform is fully loaded. This is taking the most extreme case and it would require the weight . . . . . . . . (Paper mutilated and cannot be read, but reference appears to be made to strength of cables not in direct ratio to number of wires but being less than ratio) . . . . . . . . . . This load even for a very short time, were they by any possibility subjected to it, I consider very doubtful indeed, as it is found that a wire cable made of 1000 wires banded together does not possess 1000 times the strength of a single wire, even though every wire be of the same strength. This is from the great practical difficulty in drawing them all straight alike and straining and bending them the same. This is the reason why builders generally assume so small a proportion of the breaking strain for a safe load. Of this, however, every engineer must judge for himself. It is very certain there is no economy in risk. An excess of strength is far better than a deficiency.

On the Strength of the Towers

It has been previously stated in this report that the pressure upon these towers is vertical. It will therefore be sufficient to provide for this pressure. They are built upon a firm base and of such proportions as to ensure their own stability, being built of the best material and laid in cement, it being taken for granted that the workmanship is good, of which from the fine appearance of the outside of the work I consider there is little doubt. It is proposed to demonstrate their strength. The part of the tower below the tower has the smallest sectional area. They are here six feet square containing 30 square feet in each tower, or 144 square feet collectively at the four points support. This crushing weight of granite varies from two to six tons per square inch of surface. Taking the lowest average would give us 288 tons crushing weight upon each square foot. Now as there are 144 square feet in the area of the surface of the towers we get 144 X 288 = 41,472 tons as the crushing weight of the four towers, or more than forty tons the extreme weight can by any possibility be brought upon them.

On Strength of the Anchors

Each cable is fastened by a separate attachment to its own anchors. The smallest sectional area that these attachments present is twelve and one-half inches or two shackles each two and one-half inches by two and one-half inches. There are therefore twenty attachments, of twelve inches each to the ten cables. The strain on these attachments is directly tensile. Any load applied on the bridge is immediately communicated through the cables and over the saddles to the anchors at either end. For instance, were twenty tons applied on the platform of the bridge there would be a strain of twenty tons upon each set of anchors, less the friction over the saddle. Therefore, to arrive at the strength of the anchors, only half their number must be taken into account, or one for each cable. The tensile strength of refined iron varies from sixty to eighty thousand pounds per sectional inch (according to quality). In calculations for large castings it is only considered advisable to take a sixty as a safe load. We have therefore 10 X 125 X 6000/6 = 1,250,000 pounds, 558 tons, for a safe load.

On the Strength of the Suspending Rods

There are 147 on either side of the bridge, or 294 in all. The amount of weight required to break one would be about eight tons. They have all been tested, I understand, with a strain of four tons. Before loading the bridge I subjected one to a strain of five tons striking it violently at the same time with a hammer to cause vibration. It bore this without shewing any symptoms of weakness. Assuming, therefore, eight tons to be breaking strain, taking one-quarter of this, or two tons, multiplied by the number of rods, we have 2 X 294 = 588 tons as a safe load for the rods, were this load equally distributed over the platform of the bridge. Moreover the upper and lower chords and trussed handrail have the effect of distributing any passing load over three or four of the suspending rods; and the more so on account of a certain degree of flexibility in the cable, which settles imperceptibly when the load presses heavily upon any particular point. If two of the suspension rods upon one side were taken out, leaving twelve feet of the roadway unsupported, there would still be strength enough in the chords and handrail so to distribute the load on to the two next adjoining rods, as to require about seven tons to cause fraction of the roadway.

On The Strength of the Transverse Beams

The transverse beams of the roadway which support the planking are three inches by fourteen inches in the middle rounded on top to three inches by twelve inches at the ends. From actual experiments that I have made since my return to St. Andrews, upon beams of the precise length, size of scantling and description of timber of those used in the St. John Suspension Bridge, taking the mean of those experiments, I found they broke with a dead load of four tons hung in the middle of each beam, which would be equivalent to about eight tons distributed all over the surface of the same. These beams, being covered with long three inch planks laid longitudinally, and extending over several spaces, and firmly spiked down at the crossings of each, has the effect of more than doubling the strength of an individual beam upon which there may be a pressure, (but has no effect upon the beams collectively), and moreover distributes any passing load over the adjoining beams in proportion to the length of the load. A load of three tons, including teams in one of the usual wagons of the country, would be distributed over about three beams or twelve feet. The breaking strain of these three beams (where the load is distributed) would be twenty-four tons as I have already shewn. In order to be safe, one-quarter of the breaking strain, or six tons, only should be allowed; and as a load of three tons, including teams, will always be liable to be passed by another of the same weight, I therefore consider that loads of three tons are as much as can pass one another with safety.

On the Strength of the Planking in the Roadway

The planks in the roadway are three inches thick and vary from six inches to upward of a foot in width. Their bearing between the transverse beams is three feet, nine inches. They are firmly spiked down at every crossing. The ultimate strength of a plank six inches wide, and three feet nine inches bearing, firmly fastened at each end is four tons. Taking the quarter of this, or one ton, as a safe load, it is as much weight as ever should be on a single wheel. This is while the plank is new and unworn. When the plank becomes worn down to two inches in thickness, it will then bear up only half this load, and must be removed. I consider it would have been much safer and more economical to have planked the carriage way in the middle with four inch planks, leaving the foot-paths covered as they are at present. This would have rendered the bridge much stiffer and steadier and would only have added about ten tons to its weight. There is one inch wear in a three-inch plank, for when it becomes two inches thick it must be removed; while on the other hand, there is two inches or double wear in a four inch plank. The decay need not be taken into account for in such a dry and airy position as the deck of the Suspension Bridge, good white pine plank will not suffer much from decay in less than five or six years.

Summary

No. 1.—Absolute tensile strength of cables 1125 tons

No. 2.—Suspended weight of bridge, including cables 150 tons

No. 3.—Extraneous load, theoretically, that would cause fracture 975 tons

No. 4.—Greatest extraneous load that the bridge could ever be subjected to 714 tons

No. 5.—Safe strength of cables 281 tons

No. 6.—Load that bridge will bear with perfect safety 131 tons

No. 7.—Greatest load that anchors will bear collectively with perfect safety 588 tons

No. 8.—Load that suspending rods can bear collectively with perfect safety 558 tons

No. 9.—Load that beams will bear collectively 294 tons

No. 10.—Greatest loads in tons that can pass one another with safety 3 tons

No. 11.—Greatest loads upon a wheel 1 ton

Description of the Testing

Having decided upon the safe strength of the bridge, I resolved to test the whole structure with seventy tons, or a little more than half of its safe load. This was done by means of carts loaded with bricks, in the following manner:-

Thirty carts were first placed upon the bridge, each cart and its load weighing two tons, these carts extended in double lines completely from one end of the bridge to the other, the carts upon one side not being opposite each other, but breaking joints as it were, the carts upon one side being in between two on the other. These carts were taken on one at a time, and its horse and driver allowed time to get off before another was brought on, the bridge all the time undergoing inspection to see if everything was in order. After all these carts had been placed in their position which were previously marked for them, then three double teams, weighing upwards of three tons each, were led one at a time from one end of the bridge to the other, between the double line of carts. The horses were then taken off and the whole load, amounting to about seventy tons, was left standing for an hour while the whole of the bridge underwent a close inspection without finding anything out of place. In the meantime the carts were made fast to the two lines of chains attached to the stationary power erected at either end of the bridge and were then wound simultaneously off, the last of each line of carts passing one another in the centre of the bridge, the carts upon the north side going off at the eastern end and those at the south side going off at the western end.

[End of Engineer Light’s report. Returning to William Murdoch’s text …]

On the seventh day of June, 1853, the stockholders held their first annual meeting after the shares having been distributed and paid for, about three-fourths of the total amount of £20,000 having been represented. They enacted by-laws, passed a motion to solicit help from the Province in completing the road, thanked the provisional Directors and elected their successors, as follows:-

Charles Brown, President,

Richard Whiteside, Jr., Secretary.

The Bank of New Brunswick, Treasurer.

Joseph Fairweather, Director,

William T. Ritchie, Director,

James D. Lewin, Director,

William K. Reynolds, Director.

Honourable Charles Simonds, who was one of the incorporators of the Company whose bridges fell, would seem to have lost all faith in bridge promoters. When solicited by Mr. Reynolds he refused to subscribe stock, but promised that should the promoter succeed in his enterprise he would donate him £100. Accordingly Mr. Simonds lived up to his offer, and in July, 1853, handed the lucky contractor the money.

The fondest expectations of the promoter must have been realized on the first day of September, 1853, when the right to collect tolls for one year was offered at public auction and brought the sum of £1,065, being about 9.27per cent on the £18,000 of capital stock subscribed. ‘I’he bidder, Mr. Hartwell B. Crosby, was justified in paying this price, as the receipts, during February of that year, ranged from £5 to £7 per day. This elysian era was, however, not continuous. A storm did serious damage in the spring of 1858. The description given in Harper’s Weekly of May 1st of that year with an accompanying picture of the bridge, as wrecked, and the Fredericton stage on the edge of the opening, is so vi\id that it is quoted verbatim, as follows, viz:-

(“Harper’s Weekly,” May 1st, 1858)

On 24th March a violent storm raged throughout the Province. As night fell the wind became so violent that the flooring of the bridge over the St. John River was upset and thrown into the river. The girders soon followed the example; and shortly after dark a gap of some 200 feet divided one extremity from the other. Matters were in this state when the Fredericton Coach drove, as usual, upon the bridge. The horses, which were travelling rapidly, came to a dead halt. The driver, in the storm and darkness, could see nothing; and, not unnaturally, plied the whip with some vigor. To his amazement the horses stood stock still. He whipped afresh, more severely than before; but the animals did not flinch.

With some impatience the driver got off his seat, supposing that there must be a log in the way, or that the harness was in disorder; and intending to lead his team past the doubtful point. Meanwhile the travelers inside, who, in that storm, were not in the happiest frame of mind, were loud in their reproaches and abuse of the lazy animals.

On alighting the driver could find no log in front of his team. In fact, he could see not a yard in front of him. All was blank darkness. He advanced a few steps, and finding nothing that could justify the sudden stand of the animals, turned about, resolved to lead them forward, when a sudden flash of lightning illuminated the scene. The spectacle which then shone out made his blood run cold. He was standing within a few inches of the chasm of the bridge. One step more would have precipitated him into the abyss. Had the horses not stopped when they did the coach would have gone over, and the Norwalk catastrophe would have been renewed on a smaller scale.

One can readily realize the emotion with which the driver and passengers returned thanks to the Almighty for their providential preservation from an awful death.

In the year 1875 the Government of the Province, under the powers reserved to itself in the Company’s charter, took over the bridge, paying the Company the sum of $65,000.00, and from that time on it was a free bridge, travelled constantly by the public until the new steel arch built alongside was opened and the old landmark for ever closed to travel. The work of demolition began about August 25, 1915, and was completed September 13 of the same year.

Suspension bridges may now be classed among things of the past. Their flexibility which causes a rolling load such as a locomotive to drive a wave ahead and produce the effect of a constant climbing effort, besides the racking strain on such structures, has caused their condemnation, and place has been given, by them, for the rigid type known as the Cantilever, which is of the same family and well suited to the carrying of heavy rolling loads.

In recognition of service rendered, the Provincial Government has left the foundations of the four towers which carried the bridge and, on the southern face of the southwestern one, has placed the two original inscription stones, one being “William K. Reynolds, Builder,” and the other  “Edward W. Serrell, Engineer.” In addition to these stones, a brass plate superscribed with a picture of the bridge and subscribed with the following inscription is being prepared, viz:-

This Tablet

Marks the site of the old

SUSPENSION BRIDGE

The first which spanned the River St. John.

Erected after other attempts failed.

It was for years a Toll Bridge

Then made free to the Public.

Opened for use 1853.

Removed 1915.

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Written by johnwood1946

December 5, 2012 at 10:26 AM

Posted in Uncategorized

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