Iк- PROVEMENTS IN THE CONSTRUCTION OF BRIDGES
Year: 1868

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields,
in the County of Middlesex, Gentleman, for the Invention of "Iк-
PROVEMENTS IN THE CONSTRUCTION OF BRIDGES."-A communication from
abroad by Rufus Spaulding Merrill, of Boston, in the State of
Massachusetts, in the United States of America.
Sealed the 17th November 1868, and dated the 2nd July 1868.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson
at the Office of the Commissioners of Patents, with-his Petition, on
the 2nd July 1868.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County
of Middlesex, Gentleman, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE CONSTRUCTION OF BRIDGES," a communi-
cation to me from abroad by Rufus Spaulding Merrill, of Boston, in the
State of Massachusetts, in the United States of America, to be as
follows:---
This Invention relates to a method of constructing bridges whereby
the temporary framework or scaffolding ordinarily employed to support

page_text: immediately below, thus increasing by so much the projection of the
lever.
..
use.
.
In carrying out this Invention in order to construct one set of levers
a layer of timber is first placed upon each of the piers or foundations
so as to project therefrom towards the centre of the span; upon this layer
a second layer of timber is placed rather longer than the preceeding, so
as to project in advance of the same, and upon the second a third is
placed, and so on, the projection of each successive layer being gradually
increased so as to form and arch of the desired curve until the layers meet
in the centre, when a top layer of timber is placed extending the whole
length of the bridge from shore to shore. The other set of levers being
laid in like manner and a permanent flooring added the bridge is fit for
The timbers of the several layers of which the levers are composed
may be securely attached by pins or bolts which extend down through
one or more of the layers beneath. The two set of levers may be held
together transversely by cross or bond timbers, which will not only serve
to strengthen the bridge but also to form a frame upon which a
temporary flooring may be laid for the transport of the material
required during the progress of the work. The shore ends of the
levers are weighted by means of stonework masonry or other suitable
material, so as to compensate for the increasing weight of the projecting
ends, by which means the levers may be projected without the aid of
any supports or temporary framework. beneath. In order to impart
increased stability and strength to a bridge thus constructed trusswork
may be combined with it in such a manner that the bridge itself shall
in effect constitute the bottom chord of the truss. The extremities of
the truss next on the bridge, and its top chord is firmly attached to the
bridge by means of tie rods which extend down through the various
layers of timber and are secured by means of nuts, so that the layers
of timber of which each lever and consequently the bridge is composed
constitute the bottom chord of the truss; cross pieces may be arranged in
the space between the tie rods on the top of the bridge to strengthen
and hold them in position.

page_text: According to another modification in lieu of using layers of timber
for the levers they may be composed of plates of angle iron or steel of
any suitable form, but each provided with an angle or flange at its top
and bottom to attach it to the adjacent layers. In this case each lever
is composed of two parallel sets of superposed layers of metal plates
held together by means of vertical or upright double angle iron or
H-shaped beams, to the flanges of which the plates of the several layers.
of each set are rivetted. The uprights are arranged throughout the
whole length of the lever, and extend up above the top of the bridge,
so as to form the supports of the upper chord of the truss, and the
parallel levers are connected together transversely by cross beams of
corresponding form to that of the uprights, or of any other suitable
form..
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Henry Johnson in the Great Seal Patent
Office on the 2nd January 1869..
TO ALL TO WHOM THESE PRESENTS SHALL COME,. I, JOHN
HENRY JOHNSON,, of 47, Lincoln's Inn Fields, in the County of Mid-
dlesex, Gentleman, send greeting..
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Second day of July, in the year of
our Lord One thousand eight hundred and sixty-eight, in the thirty-.
second year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said John Henry Johnson, Her special license-
that I, the said John Henry Johnson, my executors, administrators,
and assigns,, or such others as I, the said John Henry Johnson, my
executors, administrators,, or 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
THE CONSTRUCTION OF BRIDGES," a communication from abroad by Rufus
Spaulding Merrill, of Boston, in the State of Massachusetts, in the
United States of America, upon the condition (amongst others) that I,
the said John Henry Johnson, my executors or administrators, by-an

page_text: instrument in writing under my hand and seal, should particularly
describe and ascertain the nature of the said Invention, and in what
manner the same was to be performed, 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 John Henry Johnson, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement, reference being had to the accompanying
Drawings, and to the letters and figures marked thereon, that is to
say:-
The said Invention relates to a method of constructing bridges whereby
the temporary framework or scaffolding ordinarily employed to support
the main structure during the progress of the work is dispensed with,
and consists mainly in the use of two or more levers projected from the
opposite sides of the space to be spanned and mecting in the centre,
each lever being composed of a series of superposed layers, and each
layer extending a certain distance in advance of the one immediately
below, thus increasing by so much the projection of the lever.
And in order that the said Invention may be more fully understood,
I shall now proceed more particularly to describe the same, and for that
purpose shall refer to the several Figures on the annexed Sheet of
Drawings, the same letters of reference indicating corresponding parts.
in all the Figures.
Figures 1 and 2 of the accompanying Drawings represent in elevation
and plan the improved mode of constructing a bridge. The bridge may.
be considered to consist of two or more levers projected from the
opposite sides of the space to be spanned and meeting in the centre,
each lever being composed of a series of superposed layers of timbers,
and each layer extending a certain distance in advance of the one
immediately below, thus increasing by so much the projection of the
lever.
A, A, are the piers or foundations upon which the shore ends of the
levers B rest. Each lever is composed of a series of layers a, a', a³, &c.
of timbers, the bottom layer resting directly upon the base A. Upon
this layer a second layer a¹ of timbers is placed which projects in advance
of the first, as shewn in Figure 1, and upon the second layer is placed a

page_text: third a, and so on, the projection of each successive layer being
gradually increased so as to form an arch of the desired curve. The
timbers of the several layers are securely attached and held in place by
means of pins or bolts which are of sufficient length to extend down
through one, two, or even more of the layers beneath. The two
levers B, B, are held together by cross or bond timbers C, which not
only serve to strengthen the bridge but also form a frame upon which a
temporary flooring may be laid for the transportation of the material
required as the work progresses and the projection of the bridge or
levers increases. In proportion with the increase in the projection of the
levers their shore ends are weighted by means of stonework masonry
or other suitable material, so as to compensate for the increasing weight
of the projected ends, and by this means the levers may be projected
without the aid of any supports or temporary framework beneath. When
the levers thus projected from the opposite shores meet in the centre a
top layer of timbers is laid extending the whole length of the bridge
from shore to shore. The bridge is now essentially completed, and needs
only to have a permanent flooring laid in order to fit it for use; its
strength is very great, and it is built with but little expense and
consumption of time.
A bridge constructed as thus described is fitted in most respects for
ordinary use; but in order to impart to it increased stability and strength
it is proposed to combine with it trusswork in such manner that the
bridge itself shall in effect constitute the bottom chord of the truss, and
this constitutes the second part of the said Invention.
In Figures 1 and 2, D is the top chord of a truss, the extremities of
which rest upon the bridge or that part of the bridge which is supported
on the piers A. This chord is held to the bridge by means of tie rods
and nuts h, h¹, h², &c. The rods / extend down to the lower layer a of
timbers, and are attached to the timbers by means of holding nuts, as
shewn in the Drawings. The next rod extends down to and passes
through the projecting end of the succeeding layer a', and so on, each
layer of timber being held at its projecting end by one or more of the
tie rods or bolts which unite it with the top chord D. The layers of
timber of which each lever and consequently the bridge is composed
constitute therefore the bottom chord of the truss. Cross pieces or
braces E are arranged in the spaces between the tie rods on top of the
bridge so as to strengthen and hold them in position.

page_text: The third part of this Invention consists in constructing a bridge of
this class of iron or steel. This method of construction is illustrated in
Figure 3, which represents a side elevation of one of the levers of which
the bridge is composed, and in Figure 4 which is an end view of the
lever.
In order to make the bridge as light as possible without detracting
from its strength the different layers of which the lever is composed are
formed of plates of angle iron or steel rolled or otherwise formed in
the shape shewn in Figure 4, or in any other suitable form, it being
only necessary that cach plate should have at its top and bottom an
angle or flange, so that it may be rivetted to the plates of the layers next
below and above. The top and bottom flanges of the plates are indicated
by the letters m, n, and the rivets by which the top flange of the
plates of each lower layer is secured to the bottom flange of the plates
of the layer next above are marked p. Each lever is composed, as shewn
in Figure 4, of two parallel sets of superposed layers of metal playes
held together by means of vertical or upright double angle iron or
H-shaped beams F, to the flanges of which the plates of the several
layers of each set are riveted. These uprights (sec Figure 3) are
arranged throughout the whole length of the lever, and extend up above
the top of the bridge, so as to form the supports of the upper chord D
of the truss. The parallel levers B, B, are connected by cross beams G
(of the same form as the beams F), the arrangement of which will be
readily comprehended by reference to Figure 3, where they are represented
in section. A further description of this part of the said Invention is
not necessary as the principle of construction is the same as that
illustrated in Figures 1 and 2.
Having now described and particularly ascertained the nature of the
said Invention, and the manner in which the same is or may be used or
carried into effect, I would observe in conclusion that what I consider
to be novel and original, and therefore claim as the Invention secured
to me by the hercin-before in part recited Letters Patent is,
First. The method of constructing bridges by projecting one or more
levers from the same or opposite sides of the space to be spanned, in
the manner and by the means herein described.
Second. Forming the said levers of superposed layers of timbers pinned
and secured together by suitable means, each successive layer being

page_text: projected in advance of the one below until the lever has attained the
requisite length, as set forth.
Third. The combination with the double lever, constructed as herein
described of trusswork united with said lever by means of tie bolts or
rods, substantially in the manner set forth, so that the said lever shall
in effect constitute the bottom chord of the truss.
Fourth. The construction of iron and steel bridges, substantially in
the manner herein described.
In witness whereof, I, the said John Henry Johnson, have to this
my Specification set my hand and seal, this First day of January,
One thousand eight hundred and sixty-nine.
J. HENRY JOHNSON. (L.S.)