CERTAIN IMPROVEMENTS IN THE METHOD OF CONSTRUCTING MILLS AND MILL STONES FOR GRINDING
Year: 1829

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
MCCURDY, of Great James Street, Bedford Row, in the County of Middlesex,
Gentleman, send greeting.
WHEREAS, in consequence of a certain communication made to me by a
Foreigner residing abroad, I am in possession of an Invention or Discovery of
"CERTAIN IMPROVEMENTS IN THE METHOD OF CONSTRUCTING MILLS AND MILL
STONES FOR GRINDING!"..
And whereas His present most Excellent Majesty King George the
Fourth, by His Letters Patent under the Great Seal of Great Britain,
bearing date at Westminster, the Second day of November, in the tenth
year of His reign, did, for Himself, His heirs and successors, give and grant
unto me; the said John McCurdy; His special licence that 'I, the said John
McCurdy, my' executors, administrators, and assigns, or such others as I, the
said John McCurdy, my executors, adñiors, 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 expressed, should and lawfully might make, use, exercise,
and vend, within England, Wales, and the Town, of Berwick-upon-Tweed, and
also in all His said Majesty's 'Colonies and Plantations abroad, the said In-
vention; in which said Letters Patent is contained a proviso obliging me, the
said John McCurdy, by an instrument in writing under my hand and seal,
particularly to describe and: ascertain the nature of the said Invention, and in
what manner the same is to be performed; and to cause the same to be.

page_text: which is seen distinctly all the parts inclosed in the coffer of the mill. 1st,
the boulter h, which is fixed at one end to a small spout, to receive the flour as
it is discharged from between the stones, and at the other end is fixed to the
aperture at the other side of the coffer, for discharging the bran or chaff at Z.
The boulter is composed of a frame covered with boulting cloth, wire, or other
materials suitable for the purpose. K is the "go and come motion, which is
fixed moveably against the coffer of the mill, and to it is attached a bar of
wood, one end of which is inserted in the "go and come," and the other strikes
against the "tic tac" N. A small chain or rod is fastened to the middle of
this bar and also to the boulter. The "tic tac" has four branches, and is fixed
upon the lower part of the shaft of the turning stone by means of a nut and
screw, so that when the mill is in motion the "tic tac" strikes against the bar,
violently shakes the boulter, and by this means sifts the flour. The boulter is
secured by regulating screws at one end, and the other end against the coffer
of the mill. M represents the piece or bar of wood on which the point of the
shaft of the turning stone revolves upon a pivot. The shaft is regulated by a
screw at one end of the bar, and supported by a clamp at the other; and by
raising or depressing it the stones are moved at a greater or less distance from
each other, and by this means the fineness of the flour is regulated.. The point
of the shaft may revolve in a cap or socket of brass or iron, or a pin may be
fixed in the bar of wood, to work in a cavity in the lower end of the shaft of the
turning stone. This Figure also shows the thickness and diameter of the two
stones, and the manner in which the bottom stone is fixed upon the coffer, and
also the hole in the center of the bottom stone, through which the shaft passes,
which is bushed hermetically with wood between the stone and the shaft, to
prevent the grain from passing through whole into the coffer before it is ground.
It also shows the hole in the top stone about six inches in diameter; through
which the grain passes to the ground. This stone is supported by an iron bar,
fixed into the stone, and resting upon the shaft, which is called the driver, and
gives the motion to the upper stone. The dotted lines shew the distance
between the stones and their cover. Above the upper stone is also shown the
position of the trough 6, the hopper C, also the small pinion wheel V, which
is fixed upon the shaft of the turning stone. A small opening is left at W,
which can be opened and shut, and is intended to let the person who tends the
mill regulate by examination the fineness or coarseness of the flour; after
which it is permitted to, pass into the boulter.
Having now described the said new arrangement of the boulter, with refer-
ence to the stones by which I make the shaft which turns the stones give
notion to the boulter, I will proceed to describe the improved surface which

page_text: I give, to the stones, as herein-before 'alluded to. Figure 4 is the.under surface
of the upper stone. The black curved lines marked X are grooves cut in that
line.upon the stone, projected from the edge of the central holė nearly to the
outer edge of the stone; C is the iron driver or cross bar let into the stone.
-Figure 5 is a section of the upper stone from K to M. Figure 6-is a plan of
.the upper surface of the under stone. The dark parts represent pârts or
recesses chisselled out of the stone to: the depth of about. one fourth of an
:inch; so that only the light parts may be exposed to the friction of the upper
stone. Figure 7. is a section of the lower stone from H to L. Figure 8
represents a small hand-mill' for family use, of the same construction as the
*before described, except that it is on a smaller scale, and is' put. in 'motion by
manual labour by means of a crank. It may be driven with two wheels, either
horizontal or perpendicular.. It is only necessary further to state, that I use
in the mill the French burr stones; but as: these stones' are generally found in
<an imperfect state; having large holes in them, and consequently producing a
very 'imperfect grinding surface, to obviate this difficulty I employ a composi-
tion or artificial stone for the purpose of filling the holes in the stone in its
natural state, or of which to make the whole of the stones for economy, and
which composition, for the purpose of making'a grinding surface, is applicable
-to a stone of the commonest kind. For this purpose. I take the French burr
stone, and pound it into pieces of different sizes, from about a sixteenth to
.three-eighths of an inch in diameter. I then pulverize a quantity of the same
stone to the consistence of flour. I then take a quantity of alum; pounded
fine, and mix the different ingredients in the following proportion:-One sixth
of the floured stone to five parts of the broken stone, to which I add the same
weight of alum, put the whole into a vessel, and heat over the fire until the
whole are in a boiling state, and then with a ladle pour the mixture into the
hole or holes, or into the form and shape you wish to make the artificial stone,
and you will find a stone equal in quality to the French burr in its natural
state, both for hardness and for the purposes of grinding...
Now whereas I claim as the Invention aforesaid,-.
.
First, the arrangement of the boulter with reference to the stones and mode
of working it in the interior of the mill;
Secondly, the particular formed grooves cut in the lower surface of the upper
-stone, and the recesses chisselled out of the upper surface of the lower stone
as also the mode of giving a surface to stones and the composition used for
-the same, as herein-before described;
Thirdly, the mode of regulating the distance between the two stones-by the
bar and adjusting screw; and.

page_text: Fourthly, by placing stones vertically in mills; all which said several improve-
ments, being to the best of my knowledge and belief entirely new, and never
before used within that part of His said Majesty's United Kingdom of Great
Britain and Ireland called England, His said Dominion of Wales, or Town of
of Berwick-upon-Tweed, nor in any of His said Majesty's Colonies or Planta:
tions abroad: I do hereby declare this to be my Specification of the same. And
that I do verily believe this my said Specification doth comply in all respects
fully and without reserve or disguise with the proviso in the said herein-before
in part recited Letters Patent contained. Wherefore I do hereby claim to
maintain exclusive right and privilege to the said Invention.
In witness whereof, I, the said John McCurdy, have hereunto set my
hand and seal, this Twenty-eighth day of December, in the year of our
Lord One thousand eight hundred and twenty-nine.
JN° M° CURDY. (L.S.)
AND BE IT REMEMBERED, that on the Twenty-ninth day of December,
in the year of our Lord 1829, the aforesaid John McCurdy came before our
said Lord the King in His 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.
Inrolled the Second day of January, in the year of our Lord One
thousand eight hundred and thirty.