A NEW METHOD OF MAKING COFFER DAMS
Year: 1822

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, PETER
EWART, of Manchester, in the County Palatine of Lancaster, Civil Engineer,
send greeting.
WHEREAS His most Excellent Majesty King George the Fourth, by His
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Twenty-ninth day of January, in the third year of His reign,
did give and grant unto me, the said Peter Ewart, my executors, adminis-
trators, and assigns, His especial licence, full power, sole privilege and
authority, that I, the said Peter Ewart, my executors, administrators, and
assigns, during the term of years therein expressed, should and lawfully
might make, use, exercise, and vend my Invention therein mentioned, to
wit, "A NEW METHOD OF MAKING COFFER DAMS," within that part of His said
Majesty's United Kingdom of Great Britain and Ireland called England, His
Dominion of Wales, and Town of Berwick-upon-Tweed, and also in all His
said Majesty's Colonies and Plantations abroad, in such manner as to me,
the said Peter Ewart, my executors, administrators, and assigns, or any of
them, should seem meet, to have, hold, exercise, and enjoy the said licence,
powers, privileges, and advantages therein granted or mentioned to be granted
unto me, the said Peter Ewart, my executors, administrators, and assigns, for
and during and unto the full end and term of fourteen years from the date of
the said Letters Patent next and immediately ensuing, and fully to be com-
plete and ended, according to the Statute in such case made and provided;
in which said Letters Patent there is contained a proviso that if I, the
said Peter Ewart, should not particularly describe and ascertain the nature of
my said Invention, and in what manner the same is to be performed, by an

page_text: instrument in writing under my hand and seal, and cause the same to be
inrolled in His said Majesty's Higli Court. of Chancery within two calendar
months next and immediately after the date of the said Letters Patent, that
then the said Letters Patent, and all liberties and advantages whatsover
thereby granted, should utterly cease, determine, and become void, as in and by
the said recited Letters Patent, reference being thereunto had, will more fully
appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Peter Ewart, do hereby describe and ascertain the nature of my said
Invention, and the manner in which the same is to be performed, as follows,
that is to say:-
Fig. I. in the annexed Drawings or Plans, is a plain or horizontal section of
three piles or plates of cast iron, or other suitable metal or mixture of metals,
united together at their vertical joints or joinings by cramps of cast iron or
other suitable metal or mixture of metals. In this Figure there are also
shewn detached parts of the same. Fig. II. is,a horizontal plan or view of the
heads or upper parts of the same piles or plates, and cross sections of the
cramps for securing them at their vertical joints or joinings. Fig. III. is an
elevation of the same piles or plates, and the vertical cramps B, as they would
appear when viewed from the inside of a coffer dam, shewing also the hori-
zontal joints or joinings where additional lengths of piles or plates are required.
Fig. IV. is a side view of one of the same piles or plates detached at the
horizontal joint or joining. Fig. V. and VI. are different views of the cramp
and wedge for securing the piles at their horizontal joints or joinings. Fig. VII.
is a side view of one of the vertical cramps B. Fig. VIII. is a view of that part of
the same cramp which is applied next to the piles or plates. Fig. IX. is a cross
section of the lower part of the same cramp through the line o, p. Fig. X.
is a horizontal plan of the form of a coffer dam for the foundation of a pier.
Fig. XI. is a plan of part of a coffer dam, shewing how the piles or plates are
arranged round it. Fig. XII. is an end view or elevation of part of the same.
Fig. XIII. is a plan of three piles or plates, the middle one being curved to admit
of expansion and contraction in the line of piles on each side of it. Fig. XIV.
is a horizontal section of two cast metal piles or plates, united at their vertical
joints or joinings by cramps cast in one piece with the piles or plates.
Fig. XV. is a horizontal section of three piles or plates of wrought iron, united
at their vertical joints or joinings by cramps of wrought iron or casi metal.
N.B. The same characters or letters of reference are used to denote corre-
sponding parts in all the different Figures. The piles or plates A have dove-
tailed ribs or ledges a on their sides, extending the whole length of the said

page_text: piles or plates. They have also stiffening ribs b extending their whole length;
but in cases where the water is not deep, and where the ground into which
the piles or plates are to be driven is soft, and free from stones or other con-
siderable obstructions, 1 dispense with the ribs b, or I make the said piles or
plates broader or thinner than they are represented in the annexed Drawings
or Plans, putting ribs on them or not as the case may require. In other cases,
where the water is deep and the obstructions great, I make these ribs thicker
and broader, or the piles or plates stronger and narrower than they are
represented in the annexed Drawings or Plans, and with or without ribs, as
the case may require. The vertical cramps B are made to fit and slide easily
on the dove-tailed ribs or ledges a, when the piles are placed side by side, yet
sufficiently dove-tailed to retain the piles or plates in their proper situations in
relation to the cramps. The piles or plates I make in portions of various
lengthis, in general from ten to fifteen feet, but shorter or longer when required.
The vertical cramps are also made of various lengths corresponding to the
lengths of the piles or plates, along which they are continued from top to
bottom, but so that the joints or joinings of the cramps end to end shall never
be in same horizontal line with the joints or joinings of the piles or plates which
they connect. When necessary, I strengthen these cramps by making them
thicker than shewn in the annexed drawings, or by adding a rib to them, as
represented at c, Fig. 1. When an additional length of piles or plates is
required, dove-tailed projections are cast on each of the ends to be united,
which dove-tailed projections are bound together by the cramp c and wedge .
In order to make these horizontal joints or joinings water-tight, or nearly so,
three or four thicknesses of strong woollen cloth or other suitable substance
are soaked in a hot mixture of pitch and tar or other suitable composition, and
laid flat on the head of the lower portion of the pile or plate, the bottom of
the upper portion is then to be placed upon it, the cramp C to be put on its
place, and the wedge.k driven sufficiently tight to make a secure joint or
joining. For better securing the cloth in the joint or joining, there is a
groove d, Fig. IV., made in the end of the upper portion of the pile or plate in
the direction of its breadth, and in order to retain both portions more effectually
in the same place, I sometimes make cavities or mortices, as represented at e,
Figs. II. III. and IV. on the top or upper surface of each portion of the piles or
plates, and corresponding tongues or tennons t on the bottom or under surface of
each portion. When required, I make the wedge k of such a form at its point
as to be capable of turning or being turned up when driven, so that it may not
be shaken out by the shocks which the piles or plates A receive in driving.
On the cramp C a projection or tooth is cast, as represented at 2, in Fig. V.
I

page_text: and VI., and there is a corresponding notch or groove x in Fig. IV., in the dove-
tailed projection l, for the purpose of preventing the cramp C from leaving its
place on the piles or plates A, if it should be shaken loose by the shocks which
the said piles or plates receive in driving. N.B. The cloth or other sub-
stance above mentioned, interposed between the piles or plates at their
horizontal joints or joinings, must have holes cut in it to allow the tennons
to pass freely through. I make the portions of the said piles or plates of
different lengths, so that no two adjoining piles or plates shall have their
horizontal joints or joinings in the same horizontal line; indeed I prefer
having these horizontal joints or joinings two or three feet above or below
each other in adjoining piles or plates. In general I make the horizontal
joints or joinings of the vertical cramps B plain joints or joinings, having only
a groove in the end of each in the direction of its breadth, as repre-
sented at f, Fig. VII., to retain the cloth in its place, as in jointing or
joining the different portions of the piles or plates. In some cases, where
the resistance in driving is great, and where the vertical cramps are
strengthened with ribs, as at c, Fig. I., I unite their horizontal joints or
joinings with cramps and wedges, in like manner as the different portions
of the piles or plates are united by C, as before described. When the
ground into which they are to be driven is soft and presents but few obstruc-
tions, I make the points of the said piles or plates straight or chisel-shaped,
as represented at z, in Fig. XII.; but where the ground is hard and presents
considerable obstructions, I make the points, as represented in Figs. III. and IV.
When these piles or plates are cast in open sand I rivet small pieces of metal or
guides g, Figs. III., IV., XI., and XII., upon each edge, near the points thereof.
In Fig. XII., his rivetted to A, and i is rivetted to A, and each guide projects
over the edge of the pile or plate adjoining to that to which it is rivetted.
When the piles or plates are not cast in open sand, these guides are cast in
one piece with the piles or plates, as at m, on the pile or plate G, Figs. XI.
and XII. These guides tend to keep the piles from being forced out of their
places by the obstacles they may meet when driving. Fig. X. represents a
horizontal plan of a timber frame D, of a suitable form for a coffer dam for
the foundation of a pier. Two, three, or more of such frames are placed over
each other at proper distances, and secured in their proper relative situations
by upright and diagonal braces, so as to form a framework to guide and
support the said piles or plates when necessary, and to enable them to sustain
the pressure of the water. A greater or less number of such frames will be
required, according to the depth of the water where the coffer dam is to be
constructed.
This body of framework is braced firmly together before it is

page_text: put into the water. It is then moved into its proper place and sunk till it
touches the bottom, and four, or six (or more if necessary), common wooden
piles are driven in the inside of it, to which it is secured in its proper position.
For a coffer dam of the shape represented by Fig. X. I make two angle or
nose piles, one of which. is represented at G, Figs. XI. and XII.
When I place
the piles or plates ready for driving I begin by setting up one of these angles or
nose piles against one of the angles of the body of framework above described.
I then set up two of the piles or plates A against the said framing, one at
each side of the angle pile G, and put the cramps B on each of the vertical
joints or joinings. In like manner I set up or arrange the rest of the piles
or plates, and the angle or nose pile at the opposite end of the body of frame-
work, putting on their respective cramps so as to encompass the framing in
a manner similar to the staves of a cask, having provided piles or plates
of different breadths where necessary for properly completing the circuit. In
this operation each pile or plate is allowed merely to rest on its point without.
any one of them being driven until the whole circuit is completed. I provide
heads or caps of hard wood to apply or fit upon the heads of the piles or plates,
so as they may be shifted from the head of one pile or plate to the head of
another as they are wanted to be driven; these heads or caps are well hooped.
with iron, and are used for the purpose of preventing the heads of the metal
piles or plates from being broken by the blows of the ram; the said piles or
plates are then driven down in the manner in which piles of wood are com-
monly driven, care being taken that they are driven one after the other in
regular succession, so that the guides g, h, above mentioned, do not obstruct each
other. If in any part of the circuit a partial obstacle be met with opposing
too great a resistance to the piles or plates, I pull up two of the piles or
plates A of the circuit, and replace them by two others, having projections for
the purpose of uniting other piles or plates to them, as represented at H,
Fig. XI.; and I continue, if possible, a circuit of piles round the obstacle,
driving them, together with those of the main circuit, to such a depth as may
be deemed sufficient. In cases where the partial obstructions to the driving
of the piles are considerable, I surround the circuit, before any of the piles
are driven, with an iron hoop made in segments, and fastened at the joints by
upright bolts (long enough to reach from the bottom to the surface of the
water), which bolts are screwed into nuts fixed in the lower half of the joint
of the said hoop. This hoop, after being put together above water, is lowered
down till it touches the bottom, and is held in a horizontal position by
fastening the said bolts to temporary wooden or metal piles driven outside
the hoop for that purpose, and for the purpose of preventing the hoop from
being forced outwards. This hoop, supported by these outside piles, tends to

page_text: prevent the lower end of the piles or plates of the coffer dam from being
forced outwards by obstructions they may meet in entering the bottom, and the
hoop must of course be taken up before such piles or plates as H can be put.
down, and by unscrewing the bolts it may be more easily got up. In the inside
of, the lower ends or points of the cramps B are short projections », as repre-
sented in Figs. VIII. and IX., made so as nearly to fill the lower part of the
cavities (shewn black in the Drawings or Plans) which are left between the
dove-tailed ribs or ledges of the piles or plates; this short projections is for
the purpose of preventing the mud, sand, or gravel from being forced into
the said cavity while the piles or plates are driving, and a groove n is cut
across the projection, into which groove some pieces of thick leather or other
suitable substance are wedged, the leather or other suitable substance pro-
jecting so as more effectually to prevent the mud, sand, or gravel from getting
into the cavities. After all the said piles or plates are driven to such a depth
as may be deemed sufficient, the said cavities between the dove-tailed ribs or
ledges (shewn black in the Drawings or Plans) are to be carefully filled with
substances suitable for making the joints water-tight, or nearly so; oakum,
Roman cement, iron borings or turnings mixed with sharp sand, or with
pounded coal cinders, are used with effect for this purpose. When it is
essential that the surface of the piles or plates shall be kept quite even with
each other, or that the junction of their vertical joints or joinings shall be
particularly firm, I made them as represented in Fig. XIV., where there is also
a cavity in the joint or joining to be filled up with proper substances for
making the joints or joinings water-tight or nearly so, and I make the hori-
zontal joints or joinings of these last-mentioned piles or plates in the same
manner as I make the horizontal joints or joinings of the piles or plates A
before described. Where the ground into which they are to be driven
is very easily penetrated, I make piles or plates of wrought iron, and
unite their vertical joints or joinings with cramps of wrought iron or cast
metal, as represented in Fig. XV., and I unite their horizontal joints or
joinings with plates or pieces of wrought iron or cast metal in any of the
various ways in which plates of wrought iron are commonly united. In
making coffer dams for abutments of bridges, or for quays or wharf walls,
either in straight lines or curved, I use piles or plates, as herein-before
described, guiding and supporting them with frames or shores, as the case may
require. Where a sheet of coffer dam is of such extent in a strait line as
that it would be injured by the expansion and contraction of the metal, I place
at intervals curved piles or plates, as represented in Fig. XIII., for the purpose
of subdividing the effects of expansion and contraction. When occasional
openings are required for letting the water out of or into the coffer dam,

page_text: I make piles or plates, with proper openings in them, furnished with, flanches
suitable for adapting such sides and valves to the openings, as are commonly
used for admitting or excluding water. I strengthen my coffer dams, when
necessary, with banks of earth, clay, gravel, or puddle, as other coffer dams
are usually strengthened. When the piles or plates herein-before described have
been some time in the wet they become strongly united together, by the effects
of rust in addition to the pressure of the cramps, and it becomes necessary
to burst some of the joints in order to get the piles or plates up when the
coffer dam is no longer wanted. In such cases a strong iron bar, having a
conical or properly shaped steel point, is driven down the cavities (shewn
black in the Drawings or Plans), so as to burst off the cramp where that is
wanted to be done.
I do not claim as of my Invention dove-tailed ribs or ledges, cramps, or the
other separate parts of the coffer dams above described; but, my Invention
consists in the application and combination of such dove-tailed ribs or ledges,
cramps and other parts, for the purpose of making coffer dams of iron or
other suitable metal or mixture of metals.
In witness whereof, I have hereunto set my hand and seal, the Twenty-
eighth day of March, in the year of our Lord One thousand eight
hundred and twenty-two.
AND BE IT REMEMBERED, that on the Twenty-eighth day of March
in the third year of the reign of His Majesty King George the Fourth, the said
Peter Ewart came before our said Lord the King in His Chancery, and
acknowledged the Instrument aforesaid, and all and every thing therein
contained and specified, in form above written. And also the Instrument
aforesaid was stamped according to the tenor of the Statute made in the
fifty-fifth year of the reign of His late Majesty King George the Third.
Inrolled the Twenty-eighth day of March, One thousand eight hundred
and twenty turn