IMPROVEMENTS IN BRIDGES
Year: 1861

page_text: LETTERS PATENT to William Clark, of 53, Chancery Lane, in the
County of Middlesex, Engineer & Patent Agent, for the Invention of
"IMPROVEMENTS IN BRIDGES."-A communication from abroad by Mr.
Mathion Castay of Paris in the Empire of Erance. Priest.
Sealed the 14th June 1861, and dated the 14th March 1861:
PROVISIONAL SPECIFICATION left by the said William Clark at the
Office of the Commissioners of Patents, with his Petition, on the 14th
March 1861.
I, WILLIAM CLARK, of 53, Chancery Lane, in the County of Middlesex,
Engineer & Patent Agent, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN BRIDGES," to be as follows:-
This Invention relates, 1st, to the arrangement of the framework of metallic
lozenge or diagonal openwork girder bridges which are coníposed of three
longitudinal twin beams or couplings, a b, c'd, e f, Fig. 1, of any length
and width according to the strength required. These girders are of laminated
or sheet iron for metallic bridges, and of wood for wooden bridges. Between
these twin longitudinal supports a b, c d, ef, there is fixed the rods or bars of the
girder conveniently spaced and bolted or rivetted, according to the nature of the
bridge and the nature of the material, which may be of wrought or cast iron, but
better still of laminated iron reduced to the thickness of sheet iron; q, q, rods of

page_text: intersection, forming a series of lozenges, Fig. 1.; 2ndly, all the lozenge pieces
are of an H form shown in the section, Fig. 8; 3rdly, the longitudinal beams
or supports a b, c d, ef, are of the section shown in Fig. 9; 4thly, the upper
part of the girder a b, is covered with sheet iron from one end to the other;
5thly, the intermediate beams c, d, Fig. 1, are connected by stretchers or
cross bars u, x, Fig. 4, above and below, or only in the spaces of lozenge
openings; 6thly, the lower beams e, f, Fig. 1, are tied in same manner as
the middle one. If desired, sheet iron can be placed under as well as above
the girder; 7thly, the bars forming the lozenges are superposed on their
raised rib edges s, consequently their sides, p, Fig. 4, are kept apart by such
edges, cast-iron boxes are put on each side, and on each of the faces of the
beams a b, c d, frat the point of fixing f, which do not pass beyond the
edges s, but prevent the sides moving or straining at the point of contact;
8thly, the form of these parallel opipedic boxes is shown at Fig. 10, they
are lodged in the cavity formed by the raised edges on the sides of the
rods forming the lozenges and fixed 'by the holes 6. The interior space
of these boxes is fitted with partitions c, in these partitions are two
longitudinal holes a for the passage of large nails which fix the lozenge
rods to the girders f, Fig. 4, two other small holes d, Fig. 10, are intended
to afford passage to the nails which fix the parts of suspension to the girders;
9thly, Fig. 14, represents a rod or bar of the lozenge furnished with the
boxes on the side as shown; 10thly, the two boxes superposed the one
of its holes a, Fig. 10, is of a size equal to the one half of its depth (see
Fig. 13) so that the box superposed fits the projection t, Fig. 12, which
projects into the hole a, Fig. 10, thus the bearing t, Fig. 12, enters the
cylindrical hole a, Fig. 13, as far as b, which hole is only of the diameter
of the hole in t, Fig. 12, & sufficient for the passage of the bolt. The bolt
passes from the two boxes to the corresponding holes of the boxes on the
other side of the beam as thus arranged; the bolt does not wear all the
friction being on the bearing t which the bolt simply holds in position;
11thly, the assemblage of boxes is common in all superpositions of two
parts of H shape in section which are presented in the construction of these
bridges; 12thly, the upper beam a b, Fig. 1, or those of the middle c d
and the lower ones ef, have the space which exists between the twin beams
& the lozenge rods, two sections of ties of H form which are made to slide
each one in its place as represented at Fig. 5. The section e slides along
the raised rib edges of the lozenge rods c d, to e¹ & the section 9 slides
along the raised ribs of the lozenge rods a b, to g¹. To fix them in the
girders care has been taken to furnish them with smaller boxes than those

page_text: 11, which holes afford passage
placed either on the part c d,
of Fig. 10, without stud tubes being furnished only with two holes corre-.
sponding to those of the superposed boxes, Fig.
to the nails or bolts; 13thly, the platform is
of the girder Fig. 1, or the lower one e f.. The bearers of the platform-
are fixed on their flanges, the section of which is shown in Fig. 9, and are
attached to the other girders by the suspension bars or rods s³, Fig. 1;.
14thly, the transverse section of a bridge, the floor or platform of which"
is placed on the middle beams is shown at Fig. 7, while a section with the
floor on the lower girders is shown at Fig. 6; 15thly, the floor is strengthened.
underneath by the diagonal bars represented in plan, Fig. 13; 16thly, the
diagonal bars, and the principal bearers of the roadway are of H shape in
cross section and made of sheet or rolled iron; 17thly, the cross girder
beams of the roadway are not attached by ties above the roadway, but are
held in a vertical position by the struts j underneath and above the floor,"
see Figs. 6 & 7, so that the flooring rests either on the middle beams cd,
or on the lower ones ef, Fig. 1; 18thly, to augment very considerably the
strength of the girders of this system of bridge, I apply to them a wire
cable, the size of which is according to the strength of girder required;:
19thly, when the bridge is of a single span this cable turns round each
extremity of the girder, Fig. 1, in the groove of a pulley P movable on an
axis securely fixed. The extremities s of the cable are fixed to the lower
beam ef, each part of the cables to the pulley P should be as tight as
possible, this part of the cable is made fast to the lower beams at certain
distances (which can be determined according to the strength desired to
be imparted by the cable strands S) which should be as long as possible,"
and deviate as little as possible from the projection of the principal cable
S, P. The upper part of the cable Pm, naturally describes a catenarian
curve, as in suspension bridges, but with less deflection, which should be as
little as possible, and is prevented by means of supports n from the under
beam ef, to the upper part of cable Pm; 20thly, the pulley instead of
being grooved can be a toothed wheel, the teeth of which engage with a
pitch chain, to the extremities of which is attached the cable, this chain
rolls easily on the toothed wheel (see Fig. 19) & facilitates the movement.
which would not be equally free if the cable were continued intact at
that point and rolling in the groove of the pulley, as its thickness prevents
its bending readily; 21st, the cable should be as tight as possible, and to
tighten it when required its ends s can be made fast to: the lower strands s²,
and the rods of support n to the girder e f; by means of screws which permit
of the application of-tension to these lower rods or cords of support. The axes*

page_text: of pullies P may also be disposed in such way that they can be moved towards
the extremities of the girder; 22ndly, the extremitiess of the cable Fig. 1.
should be secured as much as possible towards the middle of the girder, they
can be crossed as seen in Fig. 2. Endless cables can also be used (see
Fig. 15), but then the lower strands s¹ should be double and the ends joined
to the parts S, P, of the large cable and forked as seen at Fig. 15., 23rdly,
a single cable can be put outside the girder, Figs. 1 & 2, or inside at the
side of the roadway, or even in the interior of the girder by forming the
edge rims or flanges of the lozenge rods so as to afford passage to the cable.
To render it more solid, the girders can be furnished with two cables, the
one inside & the other outside from the roadway; 24thly, in general as
many cables and apparatus thereof are nocessary as the number of arches to
a bridge, that is to say, one cable from one pier to the other for each span.
The strength of this bridge can be increased tenfold if necessary with great
economy of material, with the depth of the lozenge girders very restricted
and at same time of a span equal to upwards of a hundred yards...
Bridges with lozenge or diagonal guides having two beams or principals:-
26thly, the girder may be composed simply of two twin longitudinal beams,
a b, above and two below cd; 27thly, the two beams are attached, the one
to the other by suspension rods e, see Fig. 17, single or double & in pairs
in such way as to allow the passage of the strengthening cable; 28thly,
the section of the suspension rods e is given at Fig. 8bis; 29thly, the
beams a b, & cd, are strengthened by a series of diagonal pieces fixed to
the rods e as indicated by the dotted lines Fig. 16, or they may be arranged
in manner Fig. 17; 30thly, this system is more simple than the lozenge
shaped system before described, is more open & equally strong, it is also
less expensive as compared with the amount of materials employed, gives
enormous advantages, & can also have a cable disposed as before to strengthen
it; 31st, the diagonals instead of having a suspension rod intermediate of
each may have a rod at each alternate one; 32ndly, the floor or roadway
of these bridges is fixed to the sides and at a height indicated by science,
and as necessary for the suspension rods; 33rdly, the system of the flooring
or support of the railway is identically the same as the lozenge bridge before
described; 34thly, a section of which is shown in Fig. 38;,35thly, the
upper cable Pm, Fig. 16, rests in the groove of pulley n fixed between the
twin tie rods. In the case of a single suspension rod the pullies are fixed on
the sides of such rods; 36thly, the working of the strengthening cable when
the girder is loaded, it pulls the cable Pm, by means of the suspension
rods or pullies n, & this cable by means of the pulley. P, or the toothed, whee

page_text: before mentioned, pulls in its turn the lower part of the cable S, P, which
raises the girder & prevents its deflecting so much as it otherwise would;
37thly, it will be seen that the different systems are simple, elegant, & easy.
of execution, economical, and of a strength which to the present time, has
not been obtained.
SPECIFICATION in pursuance of the conditions of the Letters Patent
filed by the said William Clark in the Great Seal Patent Office on the
12th September 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
CLARK, of 53, Chancery Lane, in the County of Middlesex, Engineer and
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourteenth day of March in the year of our Lord
One thousand eight hundred and sixty-one, in the twenty-fourth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said William Clark, Her special licence that I, the said William Clark, my
executors, administrators, and assigns, or such others as I, the said William
Clark, my executors, administrators, and assigns, should at any time agree with,
and no others, from time to time and at all times thereafter during the term
therein expressed, should and lawfully might make, use, exercise, and vend,
within the United Kingdom of Great Britain and Ireland, the Channel Islands,
and Isle of Man, an Invention for "IMPROVEMENTS IN BRIDGES," a communication
from abroad by Mr. Mathieu Castay, of Paris, in the Empire of France,
Priest, upon the condition (amongst others) that I, the said William Clark,
my executors, or administrators, by an instrument in writing under my, or their,
or one of their hands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be per-
formed, and cause the same to be filed in the Great Seal Patent Office within
six calendar months next and immediately after the date of the said Letters
.Patent.
NOW KNOW YE, that I, the said William Clark, do hereby declare the
nature of the said Invention and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, reference being had to the Sheet of Drawings hereunto annexed, and
to the letters and figures marked thereon (that is to say):
This Invention relates, 1st, to the arrangement of the framework of bridges

page_text: which are composed of three longitudinal twin girders or couplings a b, c d, e f,
Fig. 1, of any length and width according to the strength required. These
girders are of laminated or sheet iron for metallic bridges, and of wood for
:wooden bridges. Between these twin longitudinal supports a b, c d, ef, are
fixed rods conveniently spaced, and bolted or rivetted according to the material
of the bridge, which rods may be of wrought or cast iron, but better still of
laminated iron reduced to the thickness of sheet iron; q, q, rods forming by
their intersection a series of lozenge shaped openings Fig. 1; 2nd, all these
bars are of a girder form, shown in section Fig. 8; 3rd, the longitudinal
girders or supports à b, c d, ef, are of the section shown in Fig. 9; 4th, the
upper part of the girder a, b, is covered with sheet iron from one end to the
other; 5th, the intermediate girders c, d, Fig. 1, are connected by stretchers or
'cross bars v, x, Fig. 4, above and below, or only in spaces between the lozenge
shaped openings; 6th, the lower girders e, f, Fig.1 are tied in the same manner
as the middle girders. If desired, sheet iron can be placed under as well as
above the girder as before mentioned; 7th, as the bars forming the lozenge
shaped openings are superposed on their raised edges, and consequently their
sides p, Fig. 4, are kept apart by such edges, cast-iron boxes are placed on each
side, and on each face of the girders at the point of attachment of the supports
a b, c d, which do not project beyond the edges s, but which prevent the sides
.moving or straining at the point of contact; 8th, the form of these parallelo-
piped boxes is shown at Fig. 10, they are lodged in the cavity formed by the
raised edges on the sides of the rods forming the lozenge shaped openings and
fixed thereto by the bolts 6. The interior of these boxes contains spaces s,
and partitions c; in these partitions are two cylindrical holes a for the passage
of the large bolts which fix the lozenge rods to the girders f, Fig. 4, two other
.small holes d, Fig. 10 are intended to afford passage to the bolts which fix
the parts of suspension to the girders x, Fig. 1, or supporting pillars j, Fig. 7;
9th, Fig. 14 represents a rod or bar for the lozenge openings furnished with the
-boxes on the side as shown; 10th, the two boxes superposed, the one having
holes (a, Fig. 10,) of encreased size to about one half of its depth in which a
pivot t, Fig. 12 of the box superposed fits, thus the bearing t, Fig. 12, enters
the cylindrical hole a, Fig 13, as far as b, beyond which the hole is only of
the diameter of the hole in t, Fig. 12, and sufficient for the passage of the bolts.
The bolt passes through these two boxes to corresponding holes of two
under boxes on the other side of the girder, as thus 'arranged the bolt does
not wear, all the friction being on the bearing t, which the bolt simply holds
in position in the cylindrical hole.a, Fig. 13; 11th, this method of, uniting the
boxes is adopted in all superpositions of two parts of H form in section, which

page_text: are used in the construction of these bridges; 12th; the upper girders a, b,
Fig. 1, or those of the middle c, d, & the lower ones e, f, have the space
between the twin girders and the lozenge rods fitted with two sections of ties
of H-form, which are made to slide each one in its place as represented at
Fig. 5. The section e, slides along the raised rib edges of the lozenge rods c, d,
until they reach e¹, and the section e slides along the raised ribs of the lozenge
rods a, b, & c, d, to e¹ and g¹. To fix them to the girders care should be taken
to furnish them with smaller boxes than those Fig. 10, without stud tubes,
being furnished only with two holes corresponding to those of the superposed
boxes, Fig. 11, which holes afford passage to the nails or bolts; 13th, the
platform so formed is placed either on the part c, d, of the girder, Fig. 1, or
the lower one e, f. The planking of the platform is fixed on the edges of
the girders, the section of which is shown in Fig. 9, and is attached to the
upper girders by the suspension bars s2, Fig. 1; 14th, the transverse section
of a bridge, the, floor or platform of which is placed on the girders is shown
at Fig. 6, while in section with the floor on the lower girders is shown
at Fig. 7; 15th, the floor is strengthened underneath by diagonal bars
represented in-plan Fig. 3; 16th, the diagonal bars and the principal bearers
of the roadway are of H-form in cross section, and made of sheet or rolled
iron; 17th, the girders of the roadway are not attached by ties above the
roadway, but are held in a vertical position by the struts j, underneath and
above the floor, Figs. 6 and 7, so that the flooring rests either on the
middle girders c, d, or on the lower ones e, f, (Fig. 1); 18th to augment
very considerably the resistance or strength of the girders of this system of
bridge, I apply to them a wire cable the size of which is according to the
strength of girder required; 19th, when the bridge is of a single span this
cable turns round each extremity of the compound girder, Fig. 1, in the groove
of the pulley P movable on; an axis and securely fixed. The extremities s of
the cable are fixed to the lower girders e, f, each part of the cables to the
pulley P should be as tight as possible, this part of the cable is also made
fast to the lower girders at certain distances which can be determined according
to the strength required which may be imparted by other cables or strands s¹,
which should be as long as possible and deviate as little as possible from the
projection of the principal cable S, P. The upper part of cable Pm
naturally described a catenary curve, the same as in suspension bridges,
but with less deflection, which should be as little as possible, and is pre-
vented by means of supporting rods n, which spring from the under girders
ef, and are fixed to the upper part of cable Pm; 20th, instead of a
grooved pulley toothed wheels may be employed, the teeth of which

page_text: engage in pitch chains, to the extremities of which is attached the
cable; this chain winds easily on a toothed wheel (see Fig. 19) and facilitates
the movement which would not take place if the cable were continued intact
at that point, and running in the groove of the pulley, as its thickness would
prevent its bending readily; 21st, the cable should be as tight as possible,
and to tighten it when required its ends s can be made fast to the lower
'strands s³, and the rods of support n to the girder e f, by means of screws
which permit of the application of tension to those under cords or rods of
support. The axes of pullies P may also be disposed in such way that
they can be moved towards the extremities of the girder; 22nd, the ends
"s of the cable, Fig. 1, should be secured as much as possible towards the
middle of the girder, the extremities can be crossed as seen, Fig. 2, and
endless cables can also be used, see Fig. 15, but in this case the lower
strands s¹ should be double at the ends where they are joined to the part
:S, P, of the large cable, and forked as seen at Fig. 15; 23rd, a single cable
may be placed outside the girder, Figs. 1 and 2, or inside next the roadway,
For even within the limits of the girder by forming the edge rims of the
'lozenge rods so as to afford passage for the cable. To render the structure
more solid, the two girders may each be furnished with two cables, the one
outside, and the other inside next the roadway; 24th, in general as many
cables or apparatus are necessary as there are arches to a bridge if of more
than a single span, that is to say, one cable from one pier to the other.
By the foregoing arrangements the strength of the girders may be increased
tenfold if necessary with great economy of material, while the depth of the
'compound girders may be very restricted, and at same time be of sufficient
strength for a span of upwards of a hundred yards without intermediate piers.
Bridges with two series of lozenge shaped or diagonal bars or girders.
26th, the girder may be composed simply of two twin longitudinal beams a, b,
above and two below c, d; 27th, the two beams are attached the one to the other
by single or double suspension ties e; (see Fig. 17) arranged in pairs in such
way as to allow of the passage of the strengthening cable between them;
.28th, the section of the superposed rods e is given at Fig. 8bis; 29th, the
girders a, b, and c, d, are strengthened by a series of diagonal pieces fixed to
the rods e, as indicated by the dotted lines, Fig. 16, or they may be arranged
in manner shown in Fig. 17; 30, this system is more simple than the single
series of lozenge shaped braces before described, is more open and equally
strong, it is also less expensive compared with the amount of materials
employed, & possesses the great advantage of allowing of the use of a single
cable disposed as before to strengthen it; 31st, the diagonals instead of having

page_text: suspension rods intermediate of each may have rods attached to each alternate
one; 32, the floor or roadway of these bridges is fixed to the sides & at a
height indicated by the suspension rods; 33, the system of the support or
flooring of the roadway is identically the same as the lozenge bridge for the
first arrangement, before described; 34, a section of which is shown in Fig. 18;
35, the upper cable Pm, Fig. 16, rests in the groove of pulley p, fixed on the
sides of such rods; 36, the following is the action of the strengthening cable.
When the bridge is charged with any weight it. pulls the cable Pm by
means of the suspension rods n, or pullies p, which latter or it may be a
toothed wheel as before mentioned pulls in its turn the lower cable S, P,
which raises the girder and prevents it deflecting so much as it otherwise
would; 37, from the foregoing description it will be seen that the different
systems of bridges herein described are simple, elegant, and easy of construc-
tion besides being economical, and of a strength which to the present time has
never been obtained.
Having described the nature of the Invention and the manner of per-
forming the same, I declare that what I claim as the Invention to be
protected by the herein-before in part recited Letters Patent is, the construc-
tion of the various systems of bridges herein-before described and represented
in the annexed Drawings, either of wood or iron, having cables and iron
supports, either simple or compound, applied as before described, whereby to
support the weight of the structure, the parts of which may be of much smaller
dimensions, while at same time it possesses greatly increased strength.
In witness whereof, I, the said William Clark, have hereunto set my
hand and seal, this Twelfth day of September, in the year of our Lord
One thousand eight hundred and sixty-one.