INVENTION OR IMPROVEMENT IN THE CONSTRUCTION OF A BRIDGE, BY THE FORMATION AND UNITING OF ITS COMPONENT PARTS IN A MANNER NOT HITHERTO PRACTISED
Year: 1817

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, SAMUEL
BROWN, of Mark Lane, in the City of London, Commander in His Majesty's
Royal Navy, do send greeting.
WHEREAS His most Excellent Majesty King George the Third, by His
Royal Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Tenth day of July, in the fifty-seventh year of His reign,
did give and grant unto me, the said Samuel Brown, His especial license
that I, the said Samuel Brown, my executors, administrators, and assigns, or
such others as I or they should at any time agree with, and no others, during
the term of years therein expressed, should and lawfully might make, use,
exercise, and vend, within England, Wales, and the Town of Berwick-upon-
Tweed, my
"INVENTION OR IMPROVEMENT IN THE CONSTRUCTION OF A BRIDGE,
BY THE FORMATION AND UNITING OF ITS COMPONENT PARTS IN A MANNER NOT
HITHERTO PRACTISED;" in which said Letters Patent there is contained a
proviso, obliging me, the said Samuel Brown, by an instrument in writing
under my hand and seal, particularly to describe and ascertain the nature of
my said Invention, and in what manner the same is to be performed, and to
cause the same to be inrolled in His said Majesty's High Court of Chancery
within six calendar months next and immediately after the date of the said
recited Letters Patent, as in and by the same, reference being thereto had,
will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Samuel Brown, do hereby declare that my said Invention or Improvement
consists of a bridge or bridges of suspension, in the construction of which,

page_text: instead of using metal chains formed of links, wires, or by other methods, as
heretofore practised, I employ a combination of straight bars, bolts, or rods,
joined or united at their ends either by side plates and bolts, coupling
boxes, welding, or other suitable methods, so that these bars, bolts, or rods so
joined become in effect one entire length or piece the whole extent or length
of the bridge, and support their proper proportion of the tension in the direct
line of the curve which they assume or partake of, and thesc constitute my
main lines or means of suspension. The number and consistency of these
main suspending lines must depend on the extent of the span or opening, and
the general magnitude of the design of the bridge, and each of the main sus-
pending lines may be formed of a single series of bars, bolts, or rods joined in
the manner and direction before-mentioned, or they may consist of a lateral
combination of several entire lengths of bars, bolts, or rods bound securely
together by hoops or other suitable means; and I do hereby declare that the
following description, and the Figures hereunto annexed, contain a truc account
of various methods by which my said Invention or Improvement may be carried
into effect.
To enable the public more fully to appreciate the merits of these designs, it
will be necessary for me to make some observations on the principle and effect
of bridges of suspension which have been in use prior to this Invention. The
most common are those composed of chains suspended from elevated points,
either of natural rocks, or some edifice of stone or wood, on either side of the
river or valley to be passed. There are others, more recently formed, of wires
suspended in this manner, but those are merely intended for the convenience
of foot passengers. In all bridges of the Catenarian order there must be some
similarity in the principle of forming the pieces, the points of suspension, and
securing the extremities of the chains, of whatever form these may be, and as
I
propose,
in framing this my Specification, to be very explicit on those im-
portant parts of the design, I shall at present refrain from any observations
on this head, and proceed to explain the defects and imperfections which I
conceive my Invention is calculated to obviate or remedy.
It is universally admitted that all materials will support the greatest com-
pression in a perpendicular position; so their cohesion, or the power by
which they resist being pulled asunder, is greater when acted upon in a direct
line against the force applied; and that the measure of strength of any
material, whether granulous or fibrous, is always in proportion to the area of
its section, provided the part which is subject to the action of a receding force
is uniform in its texture. It must necessarily follow, that the Catenarian curve,
composed of links, not only possesses great superfluity of weight, but that the

page_text: material is placed in a situation much less favorable for resisting the strain
than one constructed of straight bolts, bars, or rods supporting the tension in
the direction of their length, which is the nature and principle of my Invention,
as before stated. It will not be necessary to enter into any theoretical
reasoning on the subject, as the comparative weight and strength of chains;
bolts, and bars have been accurately found, by numerous corroborative experi-
ments at my manufactory, near Poplar, and an account of them, as well as of
the machine by which they were performed, is to be found in Mr. Barlow's
late work, published in London, intitled "An Essay on the Strength and Stress
of Timber." I shall, therefore, confine myself to the description of two of the
above experiments as sufficiently illustrative of the fact. A cylindrical bolt of
Welsh iron, denominated No. 3, or cable iron, measured two inches in diameter
and twelve feet six inches long, weighed one hundred and thirty-two pounds,
and required a force of eighty-two tons and three quarters to tear it asunder,
and it stretched during the operation eighteen inches and a half. A bar of
the same description of iron measured three inches in depth and one inch in
thickness, twelve feet long, weighed one hundred and twenty-four pounds, and
required a force of seventy-two tons and one quarter to pull it asunder, and
stretched thirteen inches in the process. Both the bolt and the bar are parts
of the Invention marked in Figures 3 and 4 in the accompanying Drawing.
A chain of the same sort of iron, one inch and a half diameter, twelve feet six
inches long, weighed two hundred and forty-one pounds, was broken by a force
of seventy-nine tons, and stretched during the process twenty-three inches;
thus the excess of weight was nearly double and the strength barely equal, and
as every portion of the chain between the points of suspension, indeed within'
the extremities where they are fixed, operates against its strength, the additional
weight must be considered as so much actual loss of support. It is further to
be observed, that bridges, of whatever denomination, are usually public works,
and that the chains would, in all probability, be obtained by public contract;
but from the manner in which they are usually manufactured throughout the.
country, they will not bear more than one-third of the strain of those made and
proved at the works before-mentioned; and as a bridge of chain of any
magnitude must consist of many thousand links, one superficial or unsound
sheet or welding might prove fatal to the whole fabric. In all bridges of sus-
pension, whether constructed of chains, wires, or bars, it is of the utmost
importance that every part should maintain its due portion of the tension and
weight to which the whole is subject, and the fewer the parts which compose
the great Catenarian lines, the greater is the certainty of accomplishing this
essential point. A bridge of wires, being the most complicated of any, is the

page_text: most objectionable. Where they are intended merely for the accomodation
of foot passengers they may be easily contrived and constructed; but one com-
posed of such slender and ductile materials, of sufficient strength to support
the weight of loaded carriages, must consist of such a multiplicity of parts that
an united effort by their proper adjustment is not to be expected. The want
of durability is of itself an insuperable objection to wire bridges, as well as all
others constructed of such slender filaments. The immense surface exposed to
the action of the atmosphere would infallibly cause a rapid decay, and the
common preventatives of, corrosion could not, be made generally beneficial,
because it is impossible to apply any composition to the interstices and crossings
of the wires or seams of the filaments where they are most liable to be effected;
and as the defects cannot there be observed, the bridge might be in a state of
dangerous insecurity, while it indicated no appearance of decay. The plans
which I have adopted for removing and remedying the foregoing objections
have not been hastily formed, but have been deduced from a series of expéri-
ments which I made on the comparative strength of bolts and bars and chains
of different descriptions in the year One thousand eight hundred and ciglit.
About that period I made drawings and calculations of the strength of bridges
of suspension on the precise principle of the design which is the subject of the
above recited Patent. A variety of important engagements prevented me from
making any experinients upon the design itself on a scale commerisurate to its
importance till One thousand eight hundred and thirteen, when I constructed a
bridge of straight bars for this purpose on my own premises, where it still
remains. The span or extent of this bridge is one hundred and five fect, anil
although the whole of the iron work weighs only thirty-seven hundred weight,
it has supported loaded carts and carriages of various descriptions.
Having stated the constituent principle of the Invention, I shall now preceed,
in as concise a manner as the nature of the subject will admit, to describe the
several methods of combining the component parts together, whereby the whole
is completed:
-
Fig. 1 represents a general view of a bridge upon iny plan of a span or
extent of one thousand feet. It consists of eight principal double lines of sus-
pension; the situation of which are seen at A, A, A, A, and B, B, B, B, in
Fig. 7, and four lower lines of bars for the support of the roadway, the situation
of which are seen at E, E, E, E, in the same Figure, the greatest point of
deflection, or versed sine of the curves, in the lines of bars A and B, in Figure 1,
being forty feet below their respective points of suspension C and D. The
undermost line of bars E, on which the platform or roadway is laid, are
suspended by the perpendicular bars,, a few of which are marked F, f, from

page_text: "
the upper lines A and B. Any tension on the lower lines of bars E will be
injurious unless they are extended with the same degree of curvature, or
are parallel to A. and B, in which case they would sustain their due proportion
of the strain, but then the piers and abutments would require to be con-
siderably and inconveniently heightened. I do not, therefore, allow these
under bars to draw upon the abutments; but I prefer convexing them, into
an easy curve upwards, whereby they are made of important service in
counteracting the effect of undulatory motion, which, without the reaction
of such a reversed curve or arch, is to be apprehended during the violent
storms and gusts of wind to which these bridges may be exposed. The
reversed curve or arch I recommend to rise or have a versed sine, in
the proportion of twenty feet in a thousand feet of length, which is
adjusted by the suspending bars F, f. Figure 2 represents a view of one side
pier and part of the same bridge on an enlarged scale. In order to produce
an equal bearing on all the great Catenarian lines, the perpendicular, suspending
bars F, f, F, hang alternately, by means of double key bends on the first lines
A and the second lines B. For example, the perpendicular bar No. 1, which
carries the first joint or length of the roadway.bars, passes between the double
bars B, and rests equally on the double lines of bars Aat m, and the perpen-
dicular bar No. 2 rests on the double lines of bars B at n; the perpendicular
bar No. 3 passes between the lower bars B and rests on the upper bars A at o,
and so on, throughout the structure. In this, Figure the double lines of bars
cannot be shewn, but will presently be explained by N and O in Fig. 3.
G, in Figure 3, is one of the longitudinal bars of which the great Catenarian
lines of suspension A and B are composed, it is six inches.deep by two inches
thick, and I recommend to be about fourteen feet long, or. of other suitable
lengths. The platform or roadway bars E are of the same,shape, and united
in the same manner as the principal suspending bars A and B, but as they
are free from tension they do not require to be stronger than to support the
ends of the platform beams without bending, and are half the length of the
bars above them. The ends of all the bars are to be upset or swelled out, so
that when the bolt hole is punched the surrounding metal may rather exceed
the quantity in the common section of the bar. H is one of the plates by
which the bars are united; the section of these plates should rather exceed
half the section of the main bars, the metal round the bolt hole to exceed the
general section, as in the preceeding case. I, section of a round bolt, three
inches and an half in diameter, shewn in elevation at K; by these, the coupling
plates, and the bars are attached, and are then keyed tight by the usual mode

page_text: of forelocks and washers. I, hoops, which are driven tight over the ends of the
coupling plates to bind the whole together, making the joint as stiff as the main
bar; 1, side view of the hoop; M, M is a side view of two bars coupled together,
shewing the situation of the side plates, bolts and hoops. N is a bird's-eye
view or plan of two pair of bars as they lay together in the construction 1, r,
the key head of a perpendicular suspending bar F bearing across the plates;
two such lines of these bars form one main line of suspension. O is a section
through the last Figure at r, r, showing the form of the suspending bars F,
with the double key heads above and below, and the manner in which these
rest upon the main suspending bars and support the platform bars.
Second Plan, Figure 4. The platform bars in this design are the same as
Figures 2 and 3, and the great Catenarian lines are similar, except that
cylindrical bars are used, containing the same quantity of iron, with eyes welded
instead of holes being punched, in the manner before described. The coupling
plates are also welded in the side, and made of cylindrical bolts, flattened in
the interior where the sides collapse. P represents a single cylindrical bar
with its eyes; Q, a coupling plate; R, R, section and elevation of the
joining bolts, as before; S represents two of these cylindrical bars united by
their side plates and bolts.
Third Plan. Figure 5 shews the method of forming a continuation of bolts
or bars lengthways, without welding, punching, or joining by bolts or coupling
plates. T is a bolt or bar, of fourteen feet, or other suitable length, upset at
the ends; V is one side, or the half of a pair of iron clams, with sockets reversed
to receive the heads of the bolts; U is a corresponding half, shewing the ends
of the two bolts in the sockets; W is a view of the two bolts secured in the
clams by placing them together, and driving the two hoops Z, Z, firmly over
their two ends to prevent their separating; it is in this manner that bolts or
bars are fixed at my works when their tenacity is tried by the action of opposite
forces, and I find they never break or draw in the joints so constructed. By
the above means a continuation of bolts or bars may be formed to any desired
length; the number and arrangement of the principal suspending lines, and
the platform, bars, &c., being the same as before described.
Fourth Plan. The same principle of forming the Catenarian bars may be
effected by a lateral combination of many small bars, either flat or square, but
the fewer the divisions in the section the better, because an uniform and
equal degree of tension is thereby more likely to be accomplished than by the
adjustment of a multiplicity of rods. In the present case I propose the same
numbers of principal suspending lines, composed of bars to be twenty-five feet

page_text: square; other lengths, diameters, or
Sixteen of these bars piled or laid
inches square; each of these bars is united
long and seven-eighths of an inch
dimensions may, however, be used.
together form a section of 3 and
by a hooked scarfed joint, and constitute an entire length from one extremo
point to the other. The joints of these bars need not have any distinct
binding, because the whole pile is to be secured together by hoops as at X;
and this or other proper methods of binding the bars or rods together is to be
adopted wherever a joint occurs, or at intermediate distances, if necessary, and
the joints are to be placed alternately opposite the centre of every division,
which will be effected by beginning with bars of different lengths, so that no
two bars shall be joined between the same pair of hoops. The perpendicular
suspenders in this case hang by their key heads, before described, equally on
both the great suspending bars, which I recommend to be always used in
pairs, although single bars may in some cases be adopted, and are included in
my Invention. The platform bars are the same as before-mentioned. Durability
is an object of great importance in all public works, and from the simplicity
of the construction of this bridge, there is at all times an opportunity of
applying the usual preservatives against any decay; but the period, however
remote, must arrive when it may be requisite to renew the materials, and it
will be obvious that no plan was ever executed or proposed to be executed
that affords the same opportunity of a complete and perfect restoration
without any interruption to the passage. On referring to Figure 6 it will be
seen that all the bars may be removed and new ones introduced into their
places, by which means the structure may be maintained for ever. Y is a side
view of one of the temporary side plates, which extend the length of the
three bars, and which embrace or bear upon the ends of the coupling plates,
and are secured by hoops in that situation; the holes in the sides are for the
purpose of withdrawing the bolts. The bar e and the coupling plates may
now be removed and new ones applied in their places; the temporary plates
are then shifted and fixed on the next division, as before, so that each defective
plate or bar may in successsion be renewed.
The fourth or last mentioned of the plans of my Invention does not allow
of the same facility of renewal as the three preceding ones, and as it consists
of a greater number of rods or bars there is a greater surface exposed to the
action of the atmosphere, which will not fail to penetrate into the interstices
and joints of the section in defiance of any paint or plastic composition what-
ever; it is therefore indispensably necessary to apply a more effectual or
permanent remedy; the bars should therefore first receive a coat of some

page_text: anticorrosive composition, and the seams should, as far as is practicable, be
stuffed with the same, and then each of the principal suspending lines should
be enclosed with sheet lead, the scam being undermost and soldered, so as to
form an entire pipe completely water-tight the whole length of the bridge.
The parts of those principal bars which are carried through mason's work
I-inclose in cast-iron pipes of the shape of the bars, and of sufficient strength
to withstand the pressure, but not to be attached to the bars, so as to be subject
to any tension; these cases should also be secured with lead in the joints and
made water-tight.
Although I have specified the foregoing plans as the most eligible and
effectual for carrying the Invention into effect, yet it admits of others, without
any deviation from the principle; the main suspending bars, for instance, may
be placed all parallel to each other in four upper lines, instead of the upper
and lower lines A and B, and the alternate arrangements of the perpendicular
bars be the same; but, the lower ones, which bear upon the main lines B, in
the examples already given, will, however, require to be considerably length-
ened in this case. In some cases, also, when the points of suspension are
naturally much elevated, or when they can be conveniently heightened, a more
relaxed curve may be used; and it is one of the merits of the system, that in
the combination of its constituent parts there is a great latitude of choice for
the architect or civil engineer.
.
The platform or, roadway. I construct of. wood. In the example given in-the
Drawing it consists of threo,divisions, viz., two side roads for carriages and
horses to pass.in.opposite directions, of twelve feet each, and a centre path for
foot passengers, of six feet; but these roadways may be varied in number or
dimensions or positions, to, suit the convenience of the situation. It is formed
of beams. laid crossways, the whole breadth of the bridge, which rest on the
upper edge of..the platform bars, before mentioned, and of planks laid length-
ways upon these; but instead.of using solid balks. of timber as.beams, I make
them, of two planks.laid,edgeways, twelve inches deep and three inches thick,
or such other dimensions as the weight,may require. These planks are con-
nected by chocks at intermediate distances, which keep them about three inches
asunder; the chocks, and, planks, so disposed are bound and secured together by
hoops, screw bolts, or any other suitable means. The boarding or planks for
the platform.or.floor,are.to be three inches thick, or of such, substance as the
case may require, and are, spiked. or bolted down firmly to the beams, the
whole..being in. a great measure,similar to the construction of a ship's deck.
The lower, sides of the beams are. held in their places by strong cleats or
.

page_text: hanging knees, which fit the inside. surface of the platform bars and keep
them firmly in their places; they may have straps or braces to confine them
downward upon the bars if necessary. On each side of each carriage roadway
there is a triangular piece of timber bolted down, which extends the whole
length, to prevent carriages from getting out of the proper track of the road,
as may be seen in section at a, a, in Figure 7; and the part which is exposed
to the wheel is to be covered with thin oak plank or sheathing, and iron bars
placed lengthways to prevent the main timbers from being worn away; the
centre part is also to be covered with a thin oak sheathing to save the principle
planks, and thin plates of iron must be nailed across it, not only for its
preservation, but to produce a firm foot hold for the horses. The platform is
completed by bolting securely a strong piece of timber to the ends of tho
beams and upper edge of the plank the whole length of the bridge, covering
all the butt ends and edges of the upper planks and beams, a part of which are
seen uncovered by this last-mentioned piece of timber at p, p, in Fig. 2:
The most favorable positions for building the piers of suspension are those
where the declivity of vallies or the banks of rivers are naturally formed of
rocks; they afford the greatest stability for the builder's works, and the most
secure fastening for the extremities of the main lines of suspension. The.
height of the piers will depend on the extent of the span, and the description
of ships, vessels, or other objects that may have to pass under it. To
form a passage over rivers which are not navigable, it will be merely neces-
sary to lay the foundations of the piers, and form the roadway beyond.
the reach of the highest floods; in this case the height of the piers and
points of suspension will depend altogether on the extent of the span. As.
there is nothing materially new in the manner of erecting the piers, whether
of stone, wood, or other materials, they cannot be considered as forming a
principle in the Invention in any other light than as being a connection or
application of a known mode of building to a new purpose. It will not there-
fore be necessary to enter into the minutiae of masons' or carpenters' work, but
briefly to state, that as the strength of all the main lines of suspension which
pass over the different columns or divisions of the piers greatly exceed the.
strain which they will be subject to, they may be considered as inextensible,
so the materials and the workmanship must be of that substantial nature as to
be incompressible by the weight which they have to support, and as the bridge
itself admits an entire renewal in future times, they must also be of the most
imperishable description. The piers, represented in Figure 2, are composed"
of stone, the foundation rock a substantial wooden building, on a secure

page_text: artificial foundation, although less preferable will, however, answer the purpose.
The lines through one of the piers shew the iron cases or trunks which
inclose the main suspending lines; those iron cases, as before stated, are to be
of sufficient strength to resist the internal pressure of the iron bars, bolts, &c.
which compose the Catenarian lines, as well as the outward pressure of the
materials which may rest upon or surround them. Y, beyond this pier, in
Fig. 1, represents the rock from which the piers are founded and carried out;
the dotted lines Y, Y, are channels cut through this rock in the direction that
the bars obtain on the different divisions of the piers. These channels receive
the various main suspending lines, and the extremities are secured by strong
bolts, passing through the ends of the bars, and bearing against cast-iron plates,
which are fixed as a facing to the rock. The ends of each of these cast
lengths of the Catenarian liues are provided with several bolt holes, so that
the curve of each line can be adjusted or set tight with the greatest degree of
accuracy. The most convenient mode of erecting or throwing over my bridge
of suspension is as follows:-I build a strong wooden framing upon the top of
one of the main piers on both sides, directly over the trunk or iron case, in
which the main line of suspension is to be placed. This frame is to be about
six feet higher than the front of the pier or point of supension, and continued
sloping parallel with the pier to the rock or termination of the abutments.
In front of this framing I fix a strong cast-iron roller, and at convenient
distances there are other rollers on the top of the framing, over which a chain
of suitable strength is to lead or travel. Behind the abutment I fix a capstan,
windlass, or other suitable purchase; I then begin with joining the platform
bars at the extremitiy of the abutment on the opposite side, and continue them
over the top of the framing, and if the situation is a navigable river I join the
bars on board of a suitable vessel, beginning immediately under the pier.
I employ the chain and purchase before mentioned to heave the vessel across
as the bars are fixel, letting what seamen term the bight or the united parts
hang overboard. When the bars are all fixed, and the vessel hove over as far
as the line of bars will allow, I continue to heave on the purchase and draw
the bars over the rollers on the top of the framing, and finally secure the ends
at the termination of this abutment. I previously fix at four equal distances
on this line of bars a purchase of pullics, the lower block hanging down to the
decks of four vessels moored for the purpose of heaving the bars up. I then
proceed to secure one of the main suspending bars at its extremity, and lay it
in the trunk under the temporary framing, and fix cach individual bar on
board of the vessel, and heave them across by the before-mentioned purchase..

page_text: I then attach the tackles to corresponding distances, and by simultaneous
operation of all the purchases, heave this niain. line of. bars up to its proper
elevation, and having previously fixed the opposite end -and laid the bars in
the iron trunk, I unite them at the front of the pier, and then gradually relax
the purchases and remove them from this main line; this is done by means
of a travelling stage, which is suspended to the upper lines of bars. Having
drawn up the corresponding line and fixed it in its place, I remove the
framing, purchase, &c. to the next pier or division and procced as before.
When all the main lines of suspension are drawn up and secured, I take down
the platform bars which I have employed to raise the others. As has already
been stated, I allow no tension on the platform bars; I therefore have only
occasion to use a commodious travelling stage hanging from the main suspend-
ing bars, and join the bars one by one, and introduce the perpendicular
suspenders in their corresponding situations. I then proceed to lay the beams
across and complete the platform, agreeable to the plan already described.
The first three plans may be erected in this way, but it will be necessary in
the last of those three plans to have a joint in cach main suspending line at
the point of suspension, also one at the water edge, to allow the bars to be
fixed in a horizontal direction across the river, and those two joints may be
formed in the same manner as in the cylindrical line of bars. In the fourth
plan, the bars may be drawn across singly, and each of the scarfed joints
should be secured with clasp hoops to keep them in one entire bar; and when
the lateral combination of all the bars in each line is formed, they should be
hooped tight, as already stated, and the clasp hoops in the joints may be
removed, which will permit the bars to be more closely connected. The
platform bar used in the preceding cases will be required in this, but
principally for suspending the moveable scaffold or stage, which will be
required to fix the hoops, &c., which done they may be taken down, as before,
and the travelling scaffold may be slung to the main suspending lines for
joining the platform bars and arranging the perpendicular suspenders. I
have only to add, that I strongly recommend Lieutenant Shouldham's (R. N.)
improved blocks for the purchases, as possessing very superior power, with the
least possible friction, and affording peculiar convenience in requiring a smaller
fold than any other description of pully.
In witness whereof, I, the said Samuel Brown, have hereunto set my
hand and seal, this Ninth day of January, in the year of our Lord
One thousand eight hundred and eighteen.
SAMUEL BROWN. (L.S.)

page_text: J. S. HARVEY.
AND BE IT REMEMBERED, that on the same Ninth day of January,
in the year above mentioned, the aforesaid Samuel Brown came before our
Lord the King in His Chancery, and acknowledged the Specification aforesaid,
and all and every thing therein contained, in form above written. And also
the Specification aforesaid was stamped according to the tenor of the Statute
in that case made and provided.
Inrolled the same Ninth day of January. in the year above written.