NEW INVENTED ART OR METHOD OF MANUFACTURING OR MAKING A CERTAIN COMPOSITION STONE, WHICH WILL BE EQUALLY APPLICABLE IN GRINDING OF ALL SPECIES OF CORN AND OTHER ARTICLES, AS THE MILL STONE AT PRESENT USED
Year: 1796

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, MAJOR
PRATT, of Running Waters, in the Parish of Pittington, Halgarth, in the
County Palatine of Durham, Lime Burner, do send greeting.
WHEREAS His most Excellent Majesty King George the Third, by His
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Eleventh day of March, in the thirty-sixth year of His reign, did
give and grant unto me, the said Major Pratt, my executors, administrators,
and assigns, His special licence that I, the said Major Pratt, my executors,
administrators, and assigns, during the term of years therein expressed, should
and lawfully might make, use, exercise, and vend, within England, Wales,
and the Town of Berwick-upon-Tweed, and also in all Flis Majesty's
Colonies and Plantations abroad, my "NEW INVENTED ART OR METHOD
OF MANUFACTURING OR MAKING A CERTAIN COMPOSITION STONE, WHICH WILL BE
EQUALLY APPLICABLE IN GRINDING OF ALL SPECIES OF CORN AND OTHER ARTICLES,
AS THE MILL STONE AT PRESENT USED;" in which said Letters Patent there
is contained a proviso, obliging me, the said Major Pratt, by an instrument
in writing under my hand and seal, to cause a particular description of the
nature of my said Invention, and in what manner the same is to be performed,
to be inrolled in His Majesty's High Court of Chancery within six calendar
months next and immediately after the date of the said Letters Patent, as
in and by the same (relation being thereunto had), may more fully and at large
annear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Major Pratt, do hereby declare the following to lie the nature of my said
Invention, and the manner in which it is to be performed, (that is to
say) :—
The principle of my said Invention is by mixture of siliceous and argil.
laceous earths, under certain circumstances, and by a due application of heat,
converting it into a substance capable of being formed into mill stones, or
substitutes for mill stones, answering the various purposes to which foreign
and other mill stones are now or may be applied. The proportion on which
the earths may be mixed for the purpose admits of considerable variation, as
most of the clays which are capable of being burnt into bricks are also con-
vertible to the present use. As clay and sand alone are highly refractory in
the fire, and are more liable when applied without further mixture to be
baked into bricks, or substances resembling them, than to be made to undergo
that semiortrification which qualifies them to be wrought up into millstones,
I have found it expedient to apply to them, and duly to mix with theni, a
proportion of calcareous earth previous to their being exposed to the fire.
The quantity of calcareous earth thus added may be considerably varied
without essentially altering the effect; I have found that about one-seventh
will do. Now, altho I have found it most convenient to use lime, or other
calcareous earth, for the purpose of assisting in the above process, I have
also strong reasons to apprehend that other substances, such as gypsum, the
alkaline salts, and perhaps coal, and many others, and particularly iron, will
produce a similar effect, or facilitate the operation; and besides these, other
bodies may be discovered, having the same property of assisting the fusion of
the clay and silex; but I hold all such attempts to be clearly within the
meaning and operation of my aforesaid Patent, the real discovery being that
clay and silex may, by the action of fire and by the addition of a third body.
be converted into a substance such as is above stated, and convertible into the
several uses adverted to. The degree of heat best adapted to the operation.
1 think, can only be determined by experience. I have found the heat.
employed in caleining lime adequate to the purpose; having prepared
some in an ordinary lime kiln at the same time that the lime was
burning. must observe, however, that there is a considerable difference
in the heat which different limestones require to be burnt into good lime,
and that the heat 1 employed in the above instance was rather too greit for
the limestone which I am accustomed to burn. That limestone is found by
chemical analysis to contaiu ro silex, and I know that an higher heat may
be used without materially affecting the result. . I have reason to believe;

page_text: that besides the latitude admissible in the intenseness of the heat employed
the length of time for which it is continued may be varied, and (under certain
circumstances, relating to the proportion of the different ingredients, and
probably to other causes only to be fully learnt by experience,) ought probably
to be considerably varied; I have found twenty-four hours answer. Besides
the
purposes above stated, a similar mixture of silex and argillaceous earths,
with a portion of calcareous earth, or other matter, may, as my observation
leads me to believe, be formed by the application of heat into a hard and
apparently durable substance, capable of resisting the action of the weather
for a long series of years, and as this might, when moist and soft, be made to
assume any form desired, by being put into proper moulds or otherwise it
would be convertible, in my opinion, to the purposes of ornamenting buildings,
or other uses to which stucco, &c. are now applied, and would probably prove
more durable.
In witness whereof, I, the said Major Pratt, have hereunto set my
hand and scal, this Sixth day of September, in the year of our Lord
One thousand seven hundred and ninety-six
MAJOR PRATT. (L.S.)
AND BE IT REMEMBERED, that on the same Sixth day of September,
in the year above mentioned, the aforesaid Major Pratt came before our
Lord the King in His Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained, in form above written.
And also the Specification aforesaid was stamped according to the tenor of
the Statute in that case made and provided.
Inrolled the same Ninth