IMPROVEMENTS IN THE MANU- FACTURE OF CEMENT
Year: 1865

page_text: LETTERS PATENT to Joseph Duke, of Puriton, near Bridgwater, in the
County of Somerset, for the Invention of "IMPROVEMENTS IN THE MANU-
FACTURE OF CEMENT."
Sealed the 23rd March 1866, and dated the 29th September 1865.
PROVISIONAL SPECIFICATION left by the said Joseph Duke at the
Office of the Commissioners of Patents, with his Petition, on the
29th September 1865.
I, JOSEPH DUKE, of Puriton, near Bridgwater, in the County of Somerset,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
THE MANUFACTURE OF CEMENT," to be as follows:-
This Invention has for its object improvements in the manufacture of
cement. For this purpose in manufacturing cement in character. similar to
that known as "Portland cement" the slaty limestone, schistose limestone,
limestone slate in the Grauwacke group, or the slaty limestone in the Devonian
slate deposit (such as is found in the neighbourhood of Plymouth and other
places) is employed, and is mixed and burned with clay. The proportions of
clay used will vary, depending on the quantity of lime present in the limestone.
The limestone above mentioned is ground in the raw state or after having been
burned in a kiln. The ground limestone, lime, or slaked lime is mixed with
the clay in a wash mill or in a common mortar mill. After the mixture is
dry it is burned and ground in like manner to Portland cement.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
the said Joseph Duke in the Great Seal Patent Office on the 28th
March 1866.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOSEPH
DUKE, of Puriton, near Bridgwater, in the County of Somerset, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-ninth day of September, in the year of our Lord
One thousand eight hundred and sixty-five, in the twenty-ninth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Joseph Duke, Her special licence that I, the said Joseph Duke, my
executors, administrators, and assigns, or such others as I, the said Joseph
'Duke, 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
THE MANUFACTURE OF CEMENT," upon the condition (amongst others) that I, the
said Joseph Duke, 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 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 Joseph Duke, 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
thereof, that is to say :-
This Invention has for its object improvements in the manufacture of
cement. In manufacturing bydraulic cement in character similar to that known
as "Portland cement "I employ slaty or schistose materials of a calcareous
nature, such as the slaty limestone in the Grauwacke group, schistose lime-
stone, limestone slate, or the slaty limestone in the Devonian slate deposit,
such as is found in the neighbourhood of Plymouth and in other places, or
'such limestones found in other formations. I mix such slate or schistose
materials, either in the raw or burnt state, with clay, and burn and grind the
mixture as when making Portland cement. The following is the manner in
which I prefer to proceed :-I burn the slaty material in the manner in which

page_text: limestone is usually burnt, and the resulting lime is then slacked or ground;
it is then intimately mixed with the clay in a wash mill or in a mixing
machine with sufficient water to form a pasty mass. The mixture is allowed
to remain in a heap for several days; it is then dried, burnt, and ground as is
usual in making Portland cement. The proportion in which the slaty lime
and the clay should be mixed will vary according to their composition, but
I prefer so to mix them that the compound may contain lime, alumina, and
silica in about the proportions of seven parts of lime, two parts of silica, and
one part of alumina; these proportions may however be varied. In order to
obtain these proportions it is sometimes necessary, when the slaty material is
poor in lime, to add ordinary lime to the mixture; thus if ordinary slate is
employed it will require the addition of about two parts of lime to one of
slate. In some cases also the slaty material contains an excess of alumina,
and then, in place of adding clay to it, silica, or very fine saud, or ground flint
should be substituted.
In witness whereof, I, the said Joseph Duke, have hereunto set my
hand and seal, this Twenty-sixth day of March, in the year of our
Lord One thousand eight hundred and sixty-six.
JOSEPH DUKE. (L.S.)