IMPROVEMENTS IN ARTIFICIAL STONE, MORTAR, AND CEMENTS, AND IN THE MODES OF MANUFACTURING THE SAME
Year: 1850

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME GREETING,
I, the said JOSEPH GIBBS, of Devonshire Street, Portland Place, in the County,
of Middlesex, Civil Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters.
Patent under the Great Seal of Great Britain, bearing date at Westminster,
the Seventh day of May, in the thirteenth year of Her reign, and in the.
year of our Lord One thousand eight hundred and fifty, did give and grant
unto me, the said Joseph Gibbs, my exors, adñiors, and assigns, Her especial
licence, full power, sole privilege and authority, that I, the said Joseph Gibbs,
my exors, admiors, and assigns, or such others as I, the said Joseph Gibbs,
my exors, admors, or assigns, should at any time agree with, and no others,
from time to time and at all times during the term of years therein mentioned
and expressed, should and lawfully might make, use, exercise, and vend,
within England, Wales, and the Town of Berwick-upon-Tweed, my Invention
for "IMPROVEMENTS IN ARTIFICIAL STONE, MORTAR, AND CEMENTS, AND IN THE
MODES OF MANUFACTURING THE SAME;" in which said Letters Patent is con-
tained a proviso that I, the said Joseph Gibbs, shall cause a particular
description of the nature of my said Invention, and in what manner the same
is to be performed, to be enrolled in Her said Majesty's High Court of
Chancery within six calendar months next and immediately after the date
of the said in part recited Letters Patent, as in and by the same, reference
being thereunto had, will more fully and at large appear..

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Joseph Gibbs, do hereby declare that the nature of my said Invention, and
the manner in which the same is to be performed, are particularly described
and ascertained in and by the following Instrument in writing, reference being
had to the letters and figures therein contained, and to the Drawings thereto
annexed.
Whereas the several descriptions of Roman cement are made from the septaria
of either Harwich or Sheppy, or from the septaria of the lias formation, or from
beds of cement stone found in the upper division of the lias formation, or in
the shale beds of the Kimmeridge clay. All these stones when manufactured
produce a material of a dark brown color, unfit for incrusting buildings so as
to imitate stone unless they are either colored by washes or by painting.
Now, amongst the advantages to be obtained from the cements and mortars
I have invented is this, that every description of freestone may be exactly
imitated without any wash or painting whatsoever being applied. These
cements are first calcined in kilns, and the materials are then ground between
mill stones, like those used in grinding corn for making flour. Again, the
cement called Portland cement is made by mixing clay and chalk, or river
mud and chalk, in such proportions together that the combined materials may
contain about the same proportions of lime, silica, and alumina as are found
in cements. These materials are ground together in water to a great degree
of fineness. After subsidence, and also after obtaining the proper consistency,
the pasty materials are dried in kilns or otherwise, and afterwards burned
like ordinary cements in calcining kilns. The materials are then ground in
proper mills. To these materials so prepared and so ground, are added from
one third to one half of their weight in slag of the copper smelting or other
furnaces, which combining with the lime and silica forms a cement, which is
much nearer the color of stone than any of the Roman cements heretofore
made. Now, as the combination of chalk and clay or river mud is expensive
when manufactured, and causes these cements to be very dear, and further,
as the materials are only combined mechanically and not chemically, there
is neither uniformity in their quality, nor can reliance be always placed on
their stability; the object of my Invention therefore is to lessen the expence
of manufacturing artificial stone, mortars, and cements, and produce a superior
quality of cement to those now in use.
My Invention divides itself into three parts, the first of which relates to
mortar and cements; the second to the manufacture of artificial stone; and
the third to the modes of manufacturing the said mortar, cements, and artificial
stone. I have found by extensive researches, analyses, and much experience,

page_text: that there exists in nature vast beds of argillaceous marls, and marly limestones
or marl stones, which contain the due admixture of lime, silica, and alumina,
from which hydraulic mortars, cements, and artificial stone may be manufactured.
The principal places for finding this marl and marly limestone (geologically
speaking) are the chalk formation, the Wealden formation, the Purbeck beds,
the lias formation, the. mountain limestone, and in the lowest strata of the
coal measures. In the chalk formation the marl will be found immediately
at the junction of chalk, with and just above the green sand, in that division
of the sand usually called gault, or at such places where the fire stone (or
as it is sometimes called the malm rock) exists, interposing between the gault
and the chalk marl. This chalk marl possesses a varying character, increasing
in the amount of silica and alumina as it approaches either the malm rock
or the gault; in fact, sometimes when there is no malın rock (or fire stone)
the gault becomes a calcareous marl, charged with sufficient lime to make a
cement, but the amount of the silica and alumina and lime composing the
marl can only be ascertained by experiment. The upper beds of marl and
those nearest to the greystone rock of the chalk formatiou will make hydraulic
mortar quite equal, and often superior, to. the best lias lime, and the lower
beds will make cement equal to Roman cement, except that it does not contain
a very noticeable quantity of either manganese or iron, consequently it is of
a light stone color when manufactured, and is better adapted to cover buildings
and represent stone. The chalk marl may readily be found by the springs of
water which issue from the back or escarpinent face of the chalk formation, and
above these springs (but in close proximity thereto) the hydraulic lime will. be
found, and below the springs the material for making cement must be extracted.
The proper place for obtaining the marly limestone in the Wealden formation
is in what are ternied by geologists the Ashburnham beds above and below, and
in immediate contact with the Ashburnham limestone. These limestone marls
are like perfect limestone when first extracted, but decompose by exposure to
the air after a short time. The limestone itself in particular localities some-
times become a cement stone or marl stone, which may be known by its
not slackening in water after calcination. The material for making cement
out of the beds of Purbeck limestone is obtained from some of the partings
which divide the ordinary Purbeck beds of limestone, and is. exceedingly well
calculated to make a cement of great purity and whiteness, but all the beds do
not contain in their partings the quality desired; but the proper material may be
readily found by noticing the decomposing character of the shale when exposed
to the air. The materials which I extract from the lias formation, locally called

page_text: rummell at the lime quarries at Barrow-on-Soar, in Leicestershire, is an
especial bed of marly limestone, found above and separated from all the lias
beds of limestone in that district. The same bed of rummell is found in other
districts of the lias formation, and may be readily observed on the coast of Dorset-
shire, near Lyme Regis; it is seen on the face of the limestone cliffs, embedded
in a marly shale, the whole of which decomposes after exposure to the air.
This bed of rummell has no local name in the district of Lyme Regis, not
having hitherto been applied to any useful purpose, but it may be easily found
as it exists in a deep bed of shale between the lias limestone beds and the
beds of cement stone, which heretofore have been worked, and are so now (but
the cement from this last-named stone is a deeper brown color, and unfit for
imitating stone, whilst the bed of rummell will make a cement of a light color
exactly like freestone. In such cases as when I use the hardening materials
(to be hereafter described) in combination with the calcareous marls from the
lias formation, I use some of the partings of calcareous shale existing between
the lias beds of workable limestone, provided such calcareous partings or shale
beds contain sufficient lime, which shale after calcination I combine with the
hardening materials in the manner hereafter to be directed, either by itself or
in combination with the rummell of this formation along with the hardening
materials. The materials which I extract to make cements from the moun-
tain or carboniferous limestone are only found in the upper part of that great
deposit, and must be sought for in or at the immediate junction of the limestone
shale (which shale lies under the millstone grit, and above the mountain
or carboniferous limestone dividing the two formations). These materials
consist of mountain limestone, limestone shale, and bastard limestone (that is
the limestone which will not slack after calcination, but still retains its shape
after being dipped in water). These two materials are found above the beds of
workable limestone, which beds are wrought for making ordinary limes (the
shales and the bastard limestone or limestone marl being always found together.)
These shales produce a dark cement, but the bastard limestone produces a
cement of a light stone colour, and therefore more fit for imitating stone.
In addition to these substances I extract from this formation sparry iron stone,
to make hardening material with. The materials which I extract from the
coal measures for making cement, or for mixing with the other cementitious
materials, are found only in the lowest beds of the coal measures, often con-
nected with the last two seams of coal, and before that strata joins the millstone
grit. These cementitious materials consist, first, of the coal shale (called metals
by miners) and round septaria nodules (called boilams by the local miners

page_text: about Congleton, in Cheshire). The "metals" will not in all cases make
cement, but most of them in contact with the boilams (or septaria balls) will
do so.
These boilams are composed chemically of sulphur, lime, iron, and
manganese, and are therefore easily distinguished. They are in fact a species
(as well as the "metals ") of pyrites. The "metals" and the septaria balls
make excellent cement of great hardness, but of a dark color. I use however
this cement as well as other materials in mixing with some of the cements I.
have before specified to give them hardness, the process of doing which, and
the nature of the materials, will be described hereafter. Such materials will
be called "hardening materials." When any of the materials just enumerated
are to be made into cements, the usual course of proceeding for making
cements is to be followed, that is, by burning in kilns and grinding in mills,
in the way cement is now manufactured, but I recommend that the marls and
marl stones be first dried in kilns or ovens, at a baking heat, fit for baking,
until all moisture be driven off, and that then the calcination be prolonged as
much as possible, but that the heat be kept so low as is only just sufficient to
effect complete calcination, this being indispensable to avoid the commence-
mnent of vitrification, which would destroy the adhesive properties of the
cement. These observations will be found equally applicable to kilns, such as
are now in use, or to the kiln of the improved description to be described
hereafter, and which forms part of this Invention. Although I have described
certain new materials for making cements and mortars therefrom, and which
materials are capable of forming good cements without: any admixture whatever,
yet in some cases I make a composition of the various cements, to obtain par-
ticular qualities; thus, for instance, I take a quantity of the pyrites septaria,
called boilams, and mix it with an equal quantity of the chalk marl before
described. In this case the chalk marl keeps the color light, and the septaria
or boilams of the coal measures before described gives to the chalk marl a
considerable degree of hardness. I also make a mixture of equal parts of the
bastard limestone before described for a like purpose and with the same result,
but with the rummels of the lias formation before described, or the rich argil-
laceous shale of that formation; not more than one third or one quarter part
by weight of the septaria or boilams is needful to give greater hardness and
strength to the cement made therefrom. The same observation applies to the
cement stone of the Ashburnham beds, already described, as well as the cement-
made from the interposing Purbeck shale partings. But in many cases a
cement is required of a hardness beyond what would be afforded from either
of the cement stones I have described, or the mixture of two or more of them

page_text: together, and in these cases I use substances to be combined with any of the
cement stones, or their mixtures, which I have called "hardening materials."
These materials (in addition to the one I have described, named the pyritous
septaria or boilams) consist, first, of the slag or cinder derivable from iron blast
furnaces; secondly, slag from puddle furnaces, or from reheating or mill furnaces;
thirdly, slag derivable from copper, lead, or tin furnaces; fourthly, the sparry iron
of the carboniferous strata; fifthly, the pyritous earth known by geologists as
Folkstone pyrites, which pyritous earth is a thin lamina or bead or band of earth,
in concretions just below the gault strata, and which it separates from the rock
and sand bed just below the gault. The pyrites may be found in other places in
similar positions, but the locality just indicated, namely, Folkestone in Kent, will
be a sufficient guide to find a similar material elsewhere. This pyritous earth
may be calcined in ordinary lime kilns, the same as the cement stones I have
before enumerated. If these pyrites be mixed with chalk marl or any other of
the white cement stones I have before mentioned, the imitation of stone will
be very exact, and may be sculptured afterwards with the same facility as
ordinary freestone. The same effect may be produced by mixing in the like
proportions this calcined pyritous earth with the artificial hydraulic cements
now commonly made (and which cements are composed of chalk and clay,
or mud, in due proportions, and ground together before calcination) the
pyritous earth or Folkstone pyrites displacing in this case the ground slag
with which such cements are now usually combined. The various slags and
cinders require only to be ground under edge stones to a fine powder, and
then to be mixed with any of the various cements I have enumerated, namely,
the cement from the chalk, the cement from the lias, the cement from the
Wealden and Purbeck beds, the cement from the mountain limestone, and the
cement from the coal measures. These mixtures must take place by sifting
the materials together, or by some other mode which will effectually incor-
porate and combine them, and the quantities may be generally from one
quarter (by weight) to one of slag mixed with calcareous cement.
In some
cases I grind pyritous septaria of the coal measures, or other equivalent mate-
rials (having the same chemical properties, into a fine powder, and mix such
powder with about its equal weight of some of the calcareous marls, after they
are made into cement, instead of mixing such marls with the slags or with the
calcined pyrites of Folkstone, as before directed. In other cases I mix with
the cement made from chalk or other marls, an equal weight of any of the
cements now in use, or of the calcined septaria of the London clay basin,
called Roman cement stone, more especially that part of it which is called

page_text: landstone, but in the case of using any of the septaria of the London clay
the marl and the stone may be calcined and ground together in equal propor-
tions or thereabouts.
•>
Having now described that part of my Invention which relates to the com-
position of mortar and cements, I declare that what I claim in respect thereof
is as follows:-
First, I claim the manufacture of mortar and cements from chalk marls,
the calcareous marl stones of the Ashburnham beds, the calcareous shales of
the Purbeck formation, the rummel beds of the lias formation, the calcareous
and mountain limestone shales, bastard limestone, and the "metals" and
pyritous septaria of the coal formation, all or any of them when prepared for
the purpose by grinding or pounding, and by treating with water, as before
described, and whether the same are combined or not combined with "harden-
ing materials" or other cementitious substances as aforesaid.
Second, I claim the use of the "hardening materials" before described
when used in combination with any of the calcareous substances enumerated
in the preceding claim, or in combination with any other natural calcareous
marl or marlstones.
:
Third, I claim the use of the calcined Folkstone pyritous earth, the sparry.
ironstone or white ironstone of the mountain limestone, and the calcined
pyritous septaria of the coal measures, as "hardening materials" in combination.
with any artificially-formed cement composed of chalk or lime and clay ground
and calcined, in the manner now usually practised for manufacturing artificial
cements.
Fourth, I claim the mixtures of any of the before-described marls or marl-
stones, or pyritous septaria from the coal measures, with each other, or with
any of the water cements or limes now in use, or the materials of which the
same are composed. I desire, however, to be understood, that I do not claim
the use of those cement stones which are extracted from the coal measures,
and which are usually found in connection with or above the beds of white
ironstone, and contain little or scarcely any sulpher. Neither do I claim the
use of ground slags when used in combination with slacking lime, or with
artificially-formed cement, that is, cement composed of lime and clay or mud
mixed together.
The second part of my Invention, which relates to improvements in manu-
facturing artificial stone, I perform in the following manner :-I take any of
the cements I have before described, either simple or in combination with the
hardening materials, or mixed with each other; or I take any other water
cement now in use, which may either be combined with ground limestones or
:

page_text: used by itself, as may be desired, for either fine or coarse works. The cement
selected for the purpose I put with much less than the usual quantity of water
to make it plastic into a mortar or other strong convenient vessel, and pound
it with considerable force, instead of merely mixing by hand, as is usually
practiced; and in proportion to the force applied to it in pounding, so will
the cement become indurated after setting; or instead of a mortar I use
hollow tubular hammers of large size, into the heads of which hollow hammers
I put the cement and water. The hammers are then struck with considerable
force upon some hard unyielding substance; the concussion of the blow will
cause the cement within these tubular hammers to consolidate in setting,
and become equally hardened as that which has been pounded in mortars; or
in some cases I work the cement under heavy edge runners, in the same
manner as mortar is now ground. When I desire square tubes or other
shapes to be formed, or large masses of cement to be mixed or made up, I
make a strong metallic receptacle, the interior of which will correspond with
that of the outside of the article to be formed. This receptacle is elevated
and then allowed to fall by repeated blows, the concussions of which will cause
the block or other article to be so consolidated that it will be (after standing a
short time) equal in hardness to freestone (provided the cement be good).
The block or other article may be allowed to remain for a short period
previous to taking it from the mould.
The process of pounding or of causing concussions by hollow hammers, or
by elevating and letting fall strong metallic moulds, may be carried on by
mechanical arrangements and the application of power, but as such me-
chanical arrangements are well understood by competent mechanics, they will
not require to be explained here.
When I design to make a building itself like a solid mass of stone, I first
prepare two lattices or trellises of wood, as large as one of the sides of the
building (and so.of all the rest of the building). These lattices are set up at
a distance from each other of a little less in thickness than the size of the
wall intended to be built between them. Concrete made with cement or lime,
and burnt clay broken small, or of pebbles and sand, in the usual proportions
for making concrete, are poured in between these lattices; a small portion of
this cement will exude through the openings in the lattices, and effectually key
them together. The concrete must be run horizontally in layers of about six
inches thick, and each layer must set before another layer is put on. After the
lattices are filled up the outside must then be plastered over with cement on
cach side, so as to enclose the lattices, and then the whole will be as solid and
perfect as though the building was made from one block of stone only. The

page_text: lattices may be made of wood one quarter of an inch thick and one inch wide,
leaving one inch and a quarter between them; or they may be put up like laths,
but it is not so good a method as putting them up like lattices. Of course these
dimensions may be varied according to the thickness of the wall. When it is
thought advisable to dispense with the lattices, and to make the wall without any
part of it being composed of wood, then in such cases blocks of the size of the
stone which the wall would be composed of under ordinary circumstances are to
be cast, only these blocks are to be hollow, having only sides and ends, the sides
and ends being made about two inches thick. After every course of these
blocks has been built the hollows must be filled with concrete, like that before
described. The blocks being made to break joints with each other, and being
filled with cementitious matter, the wall will become one mass of solid artificial
tone, so that there will be no necessity to put mortar between the blocks to
bed them. Instead of the blocks being cast in the shape of hollow paralle-
lograms, they may have merely a back and face, such back and face being
held together by only as such cement or other material as will keep such back
and face in parallelism with each other during the time they are setting (after
which the filling must be the same as before). It will be well to wet the
blocks before concreting cement is put in, so that they may all unite to form a
solid mass of artificial stone.
Having described the second part of my Invention, I declare that what I
claim in respect thereof is as follows:
First, I claim the process of pounding or grinding cement and materialś
mixed therewith, as before described.
Second, I claim the consolidation of cement, and materials mixed with
such cement, by concussion, as described, for forming blocks or other solid
shapes in moulds.
:
Third, I claim the process of making artificial stone by putting plastic
materials between lattices or other convenient forms, and also the methods of
casting hollow parallelograms in cement, to be afterwards filled up with
concrete for walls of artificial stone.
The third part of my Invention consists of three several improvements in the
modes of manufacturing artificial stone, mortar, and cements, which improve-
ments have for their object to effect a more perfect and rapid calcination than
can be accomplished in the kilns now in use. The kilns, especially the drawn
kilns now in use, are apt to become more heated in one part than another,
by which means some portions of the substances to be calcined are often
underburned, whilst other portions are vitrified. Now the kilns I use admit
of the most minute distribution of heat, so that all parts of the materials may

page_text: be burned equally; besides, the marls and marlstones I employ are so friable
that there is great difficulty in subjecting them to an equal calcination.
Figure 1, Sheet 1, represents a section of a square kiln; Figure 2 repre-
sents a transverse section thereof. A, A, in each Figure is the outer wall, both
Figures being lettered the same. B, B, is one of the several vaults running
under the kilns. E, E; are each one of several fireplaces, communicating
with the vaults B, B, respectively. These vaults are built, not only in the
arches and floors above the arches but also the sides or piers, with bricks of
a peculiar shape (the form of which will be described hereafter). These
bricks are to be put together without cement or other adhesive matter, so as
to admit of a free passage of air past their sides and tops. By this means one
vault cannot be materially heated more than the other, the consequence of
which will be, that the heat under the materials to be calcined must be equal,
and will be gradually distributed through the pile of calcareous substances
placed above the fire vaults. The calcining materials are represented at C, C,
and are put on the kilns through the door D, D, which door is carefully walled
up after the kiln is charged.. I am aware that vault are sometimes built
under kilns either of dry bricks or of the calcining materials themselves, ut
these vaults are of a temporary kind, and are removable on the charge of
each kiln being withdrawn; whereas the vaults I use occupy the whole area
of the kiln, and are permanent, and communicate with each other to equaliso
the heat in all directions. The upper part of the kiln may be arched from the
wall A to the wall A if it is thought advisable. After the calcination is
complete the opening to the fire vaults must be closed until the charge is
taken-out.
Figure 3 represents a brick for building the fire vaults described before;
these bricks should, for convenience, be composed of two cubes, that is, if the
brick is eight inches long it ought to four inches wide and four inches deep;
the bricks being made for the arches with a bevil conformable thereto. On
the corners of this brick, and also in the middle, there must be placed small
projections, as exemplified at A, B, C, D. The projections in the middle of
the brick must be double the lengths in the direction of the length of the
brick to those at the corners. Vaults or arches built with these bricks will
form heat space, or leave interstices between them, and communicate heat in
all directions. It is with bricks of this description that I construct the fire
vaults and other parts of the work connected with the distribution of beat.
Some of the calcareous marls I use are naturally in such a state of disintegra-
tion (especially the chalk marls), that to calcine them a kiln of any sort is
scarcely admissable. To overcome this difficulty I use a reverberatory furnace

page_text: of the construction represented in Figure 1, Sheet 2. This furnace has a
very large sole or floor on which the marl is strewn, as shewn at A; B is the
fireplace; C is the bridge; D is a passage opening to the vault E; F is the
body of the calcined materials closing the passage D; G is a door at the back
of the furnace, through which instruments can be introduced to stir up the
matters being calcined, and to push them gradually forwards towards the
passage F leading to the vault. The furnace may be fed by the door G, or by
an opening about II, as may be found convenient. Doors may also be made
in the sides of the kiln or furnace to facilitate the operation of calcination.
When large quantities of materials are required to be calcined I construct a
kiln as represented by Sheet 3, Figures 1 and 2. A, A, A, A, represents an
outer boundary wall. B, B, B, B, an inner wall not so thick, but sufficiently
so to retain the heat. C, C, C, C, the space for the materials to be piled inside.
D, D, Figure 2, is section of an inverted arch formed of bricks of the
shape represented at Figure 3. This arch has proper external openings to
communicate with and supply air to the inverted arch, and to the burning
materials. The mode of proceeding is as follows:-From E to F and G the
kiln is filled with the material to be calcined properly mixed with fuel, the
rest of the kiln being empty; as the burning proceeds the calcined material
may be taken from G, and an equal quantity of fuel and calcareous matter
may be put in the kiln at E. By proceeding in this way the operation is
continuous, and the kiln will always have the same quantity of charge in it,
and the operation will circulate all round it. If required the top of the kiln
may be vaulted over and openings may be made in the side of the kiln, but
which openings must be walled closely up on the charge coming to that
side of the kiln, except those which communicate with the inverted
arches D, D.
Having described the third part of my Invention, I declare that what I claim
in respect thereof is as follows:-
First, I claim the use of a kiln with fire vaults under the whole area of
such kiln, such vaults communicating with each other in various directions
through spaces between the bricks composing such vaults.
Second, I claim the use of a brick with projections for constructing fire
vaults, as described, for calcinating marls, marlstones, cements, and other
materials used for making hydraulic mortars.
Third, I claim the use of a circular or continuous kiln, as represented at
Figure 2, Sheet 3, for the purposes of making mortars and cements.
I make no claim, however, to kilns of an oblong or other shape, where
the fire vaults are constructed of the materials to be calcined, or where the

page_text: vaults only occupy a small part of the kiln, and do not communicate with each
other. Neither do I claim the use of a reverberatory furnace, except for the
purposes of calcining marl or marlstones for the purposes of this Invention.
In witness whereof, I, the said Joseph Gibbs, have hereunto set my
hand and seal, this Seventh day of November, in the year of our
Lord One thousand eight hundred and fifty.
JOSEPH (L.S.). GIBBS.
AND BE IT REMEMBERED; that on the Seventh day of November, in
the year of our Lord 1850, the aforesaid Joseph Gibbs came before our
said Lady the Queen in Her Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained, and specified, in form
above written. And also the Specification aforesaid was stamped according
to the tenor of the Statute made for that purpose.
Enrolled the Seventh day of November, in the year of our Lord One
thousand eight hundred and fifty.