IRON AND AND OTHER BRIDGES.
Shrewsbury being situated in the immediate neighbourhood of the
Black Country, of which coal and iron are the principal products,
Telford's attention was naturally directed, at a very early period,
to the employment of cast iron in bridge-building. The strength as
well as lightness of a bridge of this material, compared with one
of stone and lime, is of great moment where headway is ofimportance,
or the difficulties of defective foundations have to be encountered.
The metal can be moulded in such precise forms and so accurately
fitted together as to give to the arching the greatest possible
rigidity; while it defies the destructive influences of time and
atmospheric corrosion with nearly as much certainty as stone itself.
The Italians and French, who took the lead in engineering down almost
to the end of last century, early detected the value of this material,
and made several attempts to introduce it in bridge-building;
but their efforts proved unsuccessful, chiefly because of the
inability of the early founders to cast large masses of iron,
and also because the metal was then more expensive than either stone
or timber. The first actual attempt to build a cast iron bridge was
made at Lyons in 1755, and it proceeded so far that one of the
arches was put together in the builder's yard; but the project was
abandoned as too costly, and timber was eventually used.
It was reserved for English manufacturers to triumph over the
difficulties which had baffled the foreign iron-founders. Shortly
after the above ineffectual attempt had been made, the construction
of a bridge over the Severn near Broseley formed the subject of
discussion among the adjoining owners. There had been a great
increase in the coal, iron, brick, and pottery trades of the
neighbourhood; and the old ferry between the opposite banks of the
river was found altogether inadequate for the accommodation of the
traffic. The necessity for a bridge had long been felt, and the
project of constructing one was actively taken up in 1776 by
Mr. Abraham Darby, the principal owner of the extensive iron works
at Coalbrookdale. Mr. Pritchard, a Shrewsbury architect, prepared
the design of a stone bridge of one arch, in which he proposed to
introduce a key-stone of cast iron, occupying only a few feet at
the crown of the arch. This plan was, however, given up as
unsuitable; and another, with the entire arch of cast iron, was
designed under the superintendence of Mr. Darby. The castings were
made in the works at Coalbrookdale, and the bridge was erected at a
point where the banks were of considerable height on both sides of
the river. It was opened for traffic in 1779, and continues a most
serviceable structure to this day, giving the name to the town of
Ironbridge, which has sprung up in its immediate vicinity. The
bridge consists of one semicircular arch, of 100 feet span, each of
the great ribs consisting of two pieces only. Mr. Robert Stephenson
has said of the structure--"If we consider that the manipulation of
cast iron was then completely in its infancy, a bridge of such
dimensions was doubtless a bold as well as an original undertaking,
and the efficiency of the details is worthy of the boldness of the
conception."*[1]
[Image] The first Iron Bridge, Coalbrookdale.
It is a curious circumstance that the next projector of an iron
bridge--and that of a very bold design--was the celebrated, or
rather the notorious, Tom Paine, whose political writings Telford
had so much admired. The son of a decent Quaker of Thetford, who
trained him to his own trade of a staymaker, Paine seems early to
have contracted a dislike for the sect to which his father
belonged. Arrived at manhood, he gave up staymaking to embrace the
wild life of a privateersman, and served in two successive
adventures. Leaving the sea, he became an exciseman, but retained
his commission for only a year. Then he became an usher in a
school, during which he studied mechanics and mathematics. Again
appointed an exciseman, he was stationed at Lewes in Sussex, where
he wrote poetry and acquired some local celebrity as a writer.
He was accordingly selected by his brother excisemen to prepare their
petition to Government for an increase of pay, *[2] -- the document
which he drew up procuring him introductions to Goldsmith and
Franklin, and dismissal from his post. Franklin persuaded him to go
to America; and there the quondam staymaker, privateersman, usher,
poet, an a exciseman, took an active part in the revolutionary
discussions of the time, besides holding the important office of
Secretary to the Committee for Foreign Affairs. Paine afterwards
settled for a time at Philadelphia, where he occupied himself with
the study of mechanical philosophy, electricity, mineralogy, and
the use of iron in bridge-building. In 1787, when a bridge over
the Schnylkill was proposed, without any river piers, as the stream
was apt to be choked with ice in the spring freshets, Paine boldly
offered to build an iron bridge with a single arch of 400 feet
span. In the course of the same year, he submitted his design of
the proposed bridge to the Academy of Sciences at Paris; he also
sent a copy of his plan to Sir Joseph Banks for submission to the
Royal Society; and, encouraged by the favourable opinions of
scientific men, he proceeded to Rotherham, in Yorkshire, to have
his bridge cast.*[3] An American gentleman, named Whiteside, having
advanced money to Paine on security of his property in the States,
to enable the bridge to be completed, the castings were duly made,
and shipped off to London, where they were put together and
exhibited to the public on a bowling-green at Paddington.
The bridge was there visited by a large number of persons, and was
considered to be a highly creditable work. Suddenly Paine's attention
was withdrawn from its further prosecution by the publication of
Mr. Burke's celebrated 'Thoughts on the French Revolution,' which
he undertook to answer. Whiteside having in the meantime become
bankrupt, Paine was arrested by his assignees, but was liberated by
the assistance of two other Americans, who became bound for him.
Paine, however, was by this time carried away by the fervour of the
French Revolution, having become a member of the National
Convention, as representative for Calais. The "Friends of Man,"
whose cause he had espoused, treated him scurvily, imprisoning him
in the Luxembourg, where he lay for eleven months. Escaped to
America, we find him in 1803 presenting to the American Congress a
memoir on the construction of Iron Bridges, accompanied by several
models. It does not appear, however, that Paine ever succeeded in
erecting an iron bridge. He was a restless, speculative, unhappy
being; and it would have been well for his memory if, instead of
penning shallow infidelity, he had devoted himself to his original
idea of improving the communications of his adopted country.
In the meantime, however, the bridge exhibited at Paddington had
produced important results. The manufacturers agreed to take it
back as part of their debt, and the materials were afterwards used
in the construction of the noble bridge over the Wear at Sunderland,
which was erected in 1796.
The project of constructing a bridge at this place, where the rocky
banks of the Wear rise to a great height oh both sides of the
river, is due to Rowland Burdon, Esq., of Castle Eden, under whom
Mr. T. Wilson served as engineer in carrying out his design.
The details differed in several important respects from the proposed
bridge of Paine, Mr. Burdon introducing several new and original
features, more particularly as regarded the framed iron panels
radiating towards the centre in the form of voussoirs, for the
purpose of resisting compression. Mr. Phipps, C.E., in a report
prepared by him at the instance of the late Robert Stephenson,
under whose superintendence the bridge was recently repaired,
observes, with respect to the original design,--"We should probably
make a fair division of the honour connected with this unique
bridge, by conceding to Burdon all that belongs to a careful
elaboration and improvement upon the designs of another, to the
boldness of taking upon himself the great responsibility of
applying. this idea at once on so magnificent a scale, and to his
liberality and public spirit in furnishing the requisite funds
[to the amount of 22,000L.]; but we must not deny to Paine the credit
of conceiving the construction of iron bridges of far larger span
than had been made before his time, or of the important examples
both as models and large constructions which he caused to be made
and publicly exhibited. In whatever shares the merit of this great
work may be apportioned, it must be admitted to be one of the
earliest and greatest triumphs of the art of bridge construction."
Its span exceeded that of any arch then known, being 236 feet, with
a rise of 34 feet, the springing commencing at 95 feet above the
bed of the river; and its height was such as to allow vessels of
300 tons burden to sail underneath without striking their masts.
Mr. Stephenson characterised the bridge as "a structure which, as
regards its proportions and the small quantity of material employed
in its construction, will probably remain unrivalled."
[Image] Wear Bridge, at Sunderland.
The same year in which Burdon's Bridge was erected at Sunderland,
Telford was building his first iron bridge over the Severn at
Buildwas, at a point about midway between Shrewsbury and Bridgenorth.
An unusually high flood having swept away the old bridge in the
Year 1795, he was called upon, as surveyor for the county, to
supply the plan of a new one. Having carefully examined the bridge
at Coalbrookdale, and appreciated its remarkable merits, he
determined to build the proposed bridge at Buildwas of iron; and as
the waters came down with great suddenness from the Welsh mountains,
he further resolved to construct it of only one arch, so as to
afford the largest possible water-way.
He had some difficulty in inducing the Coalbrookdale iron-masters,
who undertook the casting of the girders, to depart from the plan
of the earlier structure; but he persisted in his design, which was
eventually carried out. It consisted of a single arch of 130 feet
span, the segment of a very large circle, calculated to resist the
tendency of the abutments to slide inwards, which had been a defect
of the Coalbrookdale bridge; the flat arch being itself sustained
and strengthened by an outer ribbed one on each side, springing
lower than the former and also rising higher, somewhat after the
manner of timber-trussing. Although the span of the new bridge was
30 feet wider than the Coalbrookdale bridge, it contained less than
half the quantity of iron; Buildwas bridge containing 173, whereas
the other contained 378 tons. The new structure was, besides,
extremely elegant in form; and when the centres were struck, the
arch and abutments stood perfectly firm, and have remained so to
this day. But the ingenious design of this bridge will be better
explained by the following representation than by any description
in words.*[4] The bridge at Buildwas, however, was not Telford's
first employment of iron in bridge-building; for, the year before
its erection, we find him writing to his friend at Langholm that he
had recommended an iron aqueduct for the Shrewsbury Canal,
"on a principle entirely new," and which he was "endeavouring to
establish with regard to the application of iron."*[5] This iron
aqueduct had been cast and fixed; and it was found to effect so
great a saving in masonry and earthwork, that he was afterwards
induced to apply the same principle, as we have already seen,
in different forms, in the magnificent aqueducts of Chirk and
Pont-Cysylltau.
The uses of cast iron in canal construction became more obvious
with every year's successive experience; and Telford was accustomed
to introduce it in many cases where formerly only timber or stone
had been used. On the Ellesmere, and afterwards on the Caledonial
Canal, he adopted cast iron lock-gates, which were found to answer
well, being more durable than timber, and not liable like it to
shrink and expand with alternate dryness and wet. The turnbridges
which he applied to his canals, in place of the old drawbridges,
were also of cast iron; and in some cases even the locks were of
the same material. Thus, on a part of the Ellesmere Canal opposite
Beeston Castle, in Cheshire, where a couple of locks, together
rising 17 feet, having been built on a stratum of quicksand, were
repeatedly undermined, the idea of constructing the entire locks of
cast iron was suggested; and this unusual application of the new
material was accomplished with entirely satisfactory results.
But Telford's principal employment of cast iron was in the
construction of road bridges, in which he proved himself a master.
His experience in these structures had become very extensive.
During the time that he held the office of surveyor to the county
of Salop, he erected no fewer than forty-two, five of which were of
iron. Indeed, his success in iron bridge-building so much
emboldened him, that in 1801, when Old London Bridge had become so
rickety and inconvenient that it was found necessary to take steps
to rebuild or remove it, he proposed the daring plan of a cast iron
bridge of a single arch of not less than 600 feet span, the segment
of a circle l450 feet in diameter. In preparing this design we
find that he was associated with a Mr. Douglas, to whom many
allusions are made in his private letters.*[6] The design of this
bridge seems to have arisen out of a larger project for the
improvement of the port of London. In a private letter of Telford's,
dated the 13th May, 1800, he says:
"I have twice attended the Select Committee on the Fort of London,
Lord Hawkesbury, Chairman. The subject has now been agitated for
four years, and might have been so for many more, if Mr. Pitt had
not taken the business out of the hands of the General Committee,
and got it referred to a Select Committee. Last year they
recommended that a system of docks should be formed in a large bend
of the river opposite Greenwich, called the Isle of Dogs, with a
canal across the neck of the bend. This part of the contemplated
improvements is already commenced, and is proceeding as rapidly as
the nature of the work will admit. It will contain ship docks for
large vessels, such as East and West Indiamen, whose draught of
water is considerable.
"There are now two other propositions under consideration. One is
to form another system of docks at Wapping, and the other to take
down London Bridge, rebuild it of such dimensions as to admit of
ships of 200 tons passing under it, and form a new pool for ships
of such burden between London and Blackfriars Bridges, with a set
of regular wharves on each side of the river. This is with the view
of saving lighterage and plunderage, and bringing the great mass of
commerce so much nearer to the heart of the City. This last part of
the plan has been taken up in a great measure from some statements
I made while in London last year, and I have been called before the
Committee to explain. I had previously prepared a set of plans and
estimates for the purpose of showing how the idea might be carried
out; and thus a considerable degree of interest has been excited on
the subject. It is as yet, however, very uncertain how far the
plans will be carried out. It is certainly a matter of great
national importance to render the Port of London as perfect as
possible."*[7]
Later in the same year he writes that his plans and propositions
have been approved and recommended to be carried out, and he
expects to have the execution of them. "If they will provide the
ways and means," says he, "and give me elbow-room, I see my way as
plainly as mending the brig at the auld burn." In November, 1801,
he states that his view of London Bridge, as proposed by him, has
been published, and much admired. On the l4th of April, 1802, he
writes, "I have got into mighty favour with the Royal folks. I have
received notes written by order of the King, the Prince of Wales,
Duke of York, and Duke of Kent, about the bridge print, and in
future it is to be dedicated to the King."
The bridge in question was one of the boldest of Telford's designs.
He proposed by his one arch to provide a clear headway of 65 feet
above high water. The arch was to consist of seven cast iron ribs,
in segments as large as possible, and they were to be connected by
diagonal cross-bracing, disposed in such a manner that any part of
the ribs and braces could be taken out and replaced without injury
to the stability of the bridge or interruption to the traffic over it.
The roadway was to be 90 feet wide at the abutments and 45 feet
in the centre; the width of the arch being gradually contracted
towards the crown in order to lighten the weight of the structure.
The bridge was to contain 6500 tons of iron, and the cost of the
whole was to be 262,289L.
[Image] Telford's proposed One-arched Bridge over the Thames.
The originality of the design was greatly admired, though there
were many who received with incredulity the proposal to bridge the
Thames by a single arch, and it was sarcastically said of Telford
that he might as well think of "setting the Thames on fire."
Before any outlay was incurred in building the bridge, the design
was submitted to the consideration of the most eminent scientific
and practical men of the day; after which evidence was taken at
great length before a Select Committee which sat on the subject.
Among those examined on the occasion were the venerable James Watt
of Birmingham, Mr. John Rennie, Professor Button of Woolwich,
Professors Playfair and Robison of Edinburgh, Mr. Jessop,
Mr.Southern, and Dr. Maskelyne. Their evidence will still be found
interesting as indicating the state at which constructive science
had at that time arrived in England.*[8] There was a considerable
diversity of opinion among the witnesses, as might have been
expected; for experience was as yet very limited as to the
resistance of cast iron to extension and compression. Some of them
anticipated immense difficulty in casting pieces of metal of the
necessary size and exactness, so as to secure that the radiated
joints should be all straight and bearing. Others laid down certain
ingenious theories of the arch, which did not quite square with the
plan proposed by the engineer. But, as was candidly observed by
Professor Playfair in concluding his report--"It is not from
theoretical men that the most valuable information in such a case
as the present is to be expected. When a mechanical arrangement
becomes in a certain degree complicated, it baffles the efforts of
the geometer, and refuses to submit to even the most approved
methods of investigation. This holds good particularly of bridges,
where the principles of mechanics, aided by all the resources of
the higher geometry, have not yet gone further than to determine
the equilibrium of a set of smooth wedges acting on one another by
pressure only, and in such circumstances as, except in a
philosophical experiment, can hardly ever be realised. It is,
therefore, from men educated in the school of daily practice and
experience, and who to a knowledge of general principles have
added, from the habits of their profession, a certain feeling of
the justness or insufficiency of any mechanical contrivance, that
the soundest opinions on a matter of this kind can be obtained."
It would appear that the Committee came to the general conclusion
that the construction of the proposed bridge was practicable and
safe; for the river was contracted to the requisite width, and the
preliminary works were actually begun. Mr. Stephenson says the
design was eventually abandoned, owing more immediately to the
difficulty of constructing the approaches with such a head way,
which would have involved the formation of extensive inclined
planes from the adjoining streets, and thereby led to serious
inconvenience, and the depreciation of much valuable property on
both sides of the river.*[9] Telford's noble design of his great
iron bridge over the Thames, together with his proposed embankment
of the river, being thus definitely abandoned, he fell back upon
his ordinary business as an architect and engineer, in the course
of which he designed and erected several stone bridges of
considerable magnitude and importance.
In the spring of 1795, after a long continued fall of snow, a
sudden thaw raised a heavy flood in the Severn, which carried away
many bridges--amongst others one at Bewdley, in Worcestershire,--
when Telford was called upon to supply a design for a new structure.
At the same time, he was required to furnish a plan for a new
bridge near the town of Bridgenorth; "in short," he wrote to his
friend, "I have been at it night and day." So uniform a success had
heretofore attended the execution of his designs, that his
reputation as a bridge-builder was universally acknowledged.
"Last week," he says, "Davidson and I struck the centre of an arch
of 76 feet span, and this is the third which has been thrown this
summer, none of which have shrunk a quarter of an inch."
Bewdley Bridge is a handsome and substantial piece of masonry.
The streets on either side of it being on low ground, land arches
were provided at both ends for the passage of the flood waters;
and as the Severn was navigable at the point crossed, it was
considered necessary to allow considerably greater width in the
river arches than had been the case in the former structure.
The arches were three in number--one of 60 feet span and two of 52
feet, the land arches being of 9 feet span. The works were
proceeded with and the bridge was completed during the summer of
1798, Telford writing to his friend in December of that year--
"We have had a remarkably dry summer and autumn; after that an early
fall of snow and some frost, followed by rain. The drought of the
summer was unfavourable to our canal working; but it has enabled us
to raise Bewdley Bridge as if by enchantment. We have thus built a
magnificent bridge over the Severn in one season, which is no
contemptible work for John Simpson*[10] and your humble servant,
amidst so many other great undertakings. John Simpson is a
treasure--a man of great talents and integrity. I met with him
here by chance, employed and recommended him, and he has now under
his charge all the works of any magnitude in this great and rich
district."
[Image] Bewdley Bridge.
Another of our engineer's early stone bridges, which may be
mentioned in this place, was erected by him in 1805, over the river
Dee at Tongueland in the county of Kirkcudbright. It is a bold and
picturesque bridge, situated in a lovely locality. The river is
very deep at high water there, the tide rising 20 feet. As the
banks were steep and rocky, the engineer determined to bridge the
stream by a single arch of 112 feet span. The rise being
considerable, high wingwalls and deep spandrels were requisite; but
the weight of the structure was much lightened by the expedient
which he adopted of perforating the wings, and building a number of
longitudinal walls in the spandrels, instead of filling them with
earth or inferior masonry, as had until then been the ordinary
practice. The ends of these walls, connected and steadied by the
insertion of tee-stones, were built so as to abut against the back
of the arch-stones and the cross walls of each abutment. Thus great
strength as well as lightness was secured, and a very graceful and
at the same time substantial bridge was provided for the
accommodation of the district.*[11]
[Image] Tongueland Bridge.
In his letters written about this time, Telford seems to have been
very full of employment, which required him to travel about a great
deal. "I have become," said he, "a very wandering being, and am
scarcely ever two days in one place, unless detained by business,
which, however, occupies my time very completely." At another time
he says, "I am tossed about like a tennis ball: the other day I was
in London, since that I have been in Liverpool, and in a few days I
expect to be at Bristol. Such is my life; and to tell you the
truth, I think it suits my disposition."
Another work on which Telford was engaged at this time was a
project for supplying the town of Liverpool with water conveyed
through pipes in the same manner as had long before been adopted in
London. He was much struck by the activity and enterprise apparent
in Liverpool compared with Bristol. "Liverpool," he said,
"has taken firm root in the country by means of the canals"
it is young, vigorous, and well situated. Bristol is sinking in
commercial importance: its merchants are rich and indolent, and in
their projects they are always too late. Besides, the place is
badly situated. There will probably arise another port there
somewhat nearer the Severn; but Liverpool will nevertheless
continue of the first commercial importance, and their water will
be turned into wine. We are making rapid progress in this country--
I mean from Liverpool to Bristol, and from Wales to Birmingham.
This is an extensive and rich district, abounding in coal, lime,
iron, and lead. Agriculture too is improving, and manufactures
are advancing at rapid strides towards perfection. Think of such a
mass of population, industrious, intelligent, and energetic, in
continual exertion! In short, I do not believe that any part of the
world, of like dimensions, ever exceeded Great Britain, as it now
is, in regard to the production of wealth and the practice of the
useful arts."*[12] Amidst all this progress, which so strikingly
characterized the western districts of England, Telford also
thought that there was a prospect of coming improvement for Ireland.
"There is a board of five members appointed by Parliament, to act
as a board of control over all the inland navigations, &c., of
Ireland. One of the members is a particular friend of mine, and at
this moment a pupil, as it were, anxious for information. This is
a noble object: the field is wide, the ground new and capable of
vast improvement. To take up and manage the water of a fine island
is like a fairy tale, and, if properly conducted, it would render
Ireland truly a jewel among the nations."*[13] It does not,
however, appear that Telford was ever employed by the board to
carry out the grand scheme which thus fired his engineering
imagination.
Mixing freely with men of all classes, our engineer seems to have
made many new friends and acquaintances about this time. While on
his journeys north and south, he frequently took the opportunity of
looking in upon the venerable James Watt--"a great and good man,"
he terms him--at his house at Heathfield, near Birmingham.
At London he says he is "often with old Brodie and Black, each the
first in his profession, though they walked up together to the
great city on foot,*[14] more than half a century ago--Gloria!"
About the same time we find him taking interest in the projects of
a deserving person, named Holwell, a coal-master in Staffordshire,
and assisting him to take out a patent for boring wooden pipes;
"he being a person," says Telford, "little known, and not having
capital, interest, or connections, to bring the matter forward."
Telford also kept up his literary friendships and preserved his
love for poetical reading. At Shrewsbury, one of his most intimate
friends was Dr. Darwin, son of the author of the 'Botanic Garden.'
At Liverpool, he made the acquaintance of Dr. Currie, and was
favoured with a sight of his manuscript of the ' Life of Burns,'
then in course of publication. Curiously enough, Dr. Currie had
found among Burns's papers a copy of some verses, addressed to the
poet, which Telford recognised as his own, written many years
before while working as a mason at Langholm. Their purport was to
urge Burns to devote himself to the composition of poems of a
serious character, such as the 'Cotter's Saturday Night.' With
Telford's permission, several extracts from his Address to Burns
were published in 1800 in Currie's Life of the poet. Another of
his literary friendships, formed about the same time, was that with
Thomas Campbell, then a very young man, whose 'Pleasures of Hope'
had just made its appearance. Telford, in one of his letters, says,
"I will not leave a stone unturned to try to serve the author of
that charming poem. In a subsequent communication*[15] he says,
"The author of the 'Pleasures of Hope' has been here for some time.
I am quite delighted with him. He is the very spirit of poetry.
On Monday I introduced him to the King's librarian, and I imagine
some good may result to him from the introduction."
In the midst of his plans of docks, canals, and bridges, he wrote
letters to his friends about the peculiarities of Goethe's poems
and Kotzebue's plays, Roman antiquities, Buonaparte's campaign in
Egypt, and the merits of the last new book. He confessed, however,
that his leisure for reading was rapidly diminishing in consequence
of the increasing professional demands upon his time; but he bought
the 'Encyclopedia Britannica,' which he described as "a perfect
treasure, containing everything, and always at hand." He thus
rapidly described the manner in which his time was engrossed.
"A few days since, I attended a general assembly of the canal
proprietors in Shropshire. I have to be at Chester again in a
week, upon an arbitration business respecting the rebuilding of the
county hall and gaol; but previous to that I must visit Liverpool,
and afterwards proceed into Worcestershire. So you see what sort
of a life I have of it. It is something like Buonaparte, when in
Italy, fighting battles at fifty or a hundred miles distance every
other day. However, plenty of employment is what every
professional man is seeking after, and my various occupations now
require of me great exertions, which they certainly shall have so
long as life and health are spared to me."*[16] Amidst all his
engagements, Telford found time to make particular inquiry about
many poor families formerly known to him in Eskdale, for some of
whom he paid house-rent, while he transmitted the means of
supplying others with coals, meal, and necessaries, during the
severe winter months,--a practice which he continued to the close
of his life.
Footnotes for Chapter VII.
*[1] 'Encyclopedia Britannica,' 8th ed. Art. "Iron Bridges."
*[2] According to the statement made in the petition drawn by Paine,
excise officers were then (1772) paid only 1s. 9 1/4d. a day.
*[3] In England, Paine took out a patent for his Iron Bridge in
1788. Specification of Patents (old law) No. 1667.
*[4] [Image] Buildwas Bridge.
The following are further details: "Each of the main ribs of the
flat arch consists of three pieces, and at each junction they are
secured by a grated plate, which connects all the parallel ribs
together into one frame. The back of each abutment is in a
wedge-shape, so as to throw off laterally much of the pressure of
the earth. Under the bridge is a towing path on each side of the
river. The bridge was cast in an admirable manner by the
Coalbrookdale iron-masters in the year 1796, under contract with
the county magistrates. The total cost was 6034L. l3s. 3d."
*[5] Letter to Mr. Andrew Little, Langholm, dated Shrewsbury,
l8th March, 1795.
*[6] Douglas was first mentioned to Telford, in a letter from
Mr. Pasley, as a young man, a native of Bigholmes, Eskdale, who had,
after serving his time there as a mechanic, emigrated to America,
where he showed such proofs of mechanical genius that he attracted
the notice of Mr. Liston, the British Minister, who paid his
expenses home to England, that his services might not be lost to
his country, and at the same time gave him a letter of introduction
to the Society of Arts in London. Telford, in a letter to Andrew
Little, dated 4th December, 1797, expressed a desire "to know more
of this Eskdale Archimedes." Shortly after, we find Douglas
mentioned as having invented a brick machine, a shearing-machine,
and a ball for destroying the rigging of ships; for the two former
of which he secured patents. He afterwards settled in France, where
he introduced machinery for the improved manufacture of woollen
cloth; and being patronised by the Government, he succeeded in
realising considerable wealth, which, how ever, he did not live to
enjoy.
*[7] Letter to Mr. Andrew Little, Langholm, dated London, l3th May,
1800.
*[8] The evidence is fairly set forth in 'Cresy's Encyclopedia of
Civil Engineering,' p. 475.
*[9] Article on Iron Bridges, in the 'Encyclopedia Britannica,'
Edinburgh, 1857.
*[10] His foreman of masons at Bewdley Bridge, and afterwards his
assistant in numerous important works.
*[11] The work is thus described in Robert Chambers's ' Picture of
Scotland':--"Opposite Compston there is a magnificent new bridge
over the Dee. It consists of a single web, the span of which is 112
feet; and it is built of vast blocks of freestone brought from the
isle of Arran. The cost of this work was somewhere about 7000L.
sterling; and it may be mentioned, to the honour of the Stewartry,
that this sum was raised by the private contributions of the
gentlemen of the district. From Tongueland Hill, in the immediate
vicinity of the bridge, there is a view well worthy of a painter's
eye, and which is not inferior in beauty and magnificence to any in
Scotland."
*[12] Letter to Mr. Andrew Little, Langholm, dated Salop,
13th July, 1799.
*[13] Letter to Mr. Andrew Little, Langholm, dated Liverpool,
9th September, 1800.
*[14] Brodie was originally a blacksmith. He was a man of much
ingenuity and industry, and introduced many improvements in iron
work; he invented stoves for chimneys, ships' hearths, &c. He had
above a hundred men working in his London shop, besides carrying on
an iron work at Coalbrookdale. He afterwards established a woollen
manufactory near Peebles.
*[15] Dated London, l4th April, 1802.
*[16] Letter to Mr. Andrew Little, Langholm, dated Salop,
30th November, 1799.