MAKING SCREWS AND MACHINES FOR DIVIDING OF MATHEMATICAL INSTRUMENTS FROM THE SAID SCREWS
Year: 1778

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, WILLIAM
HARRISON, of Lambs Conduit Street, in the County of Middlesex, Esquire,
and PETER ATHERTON, of the Parish of Saint Sepulchre, London, Watch Tool
Maker, send greeting.
WHEREAS the King's most Excellent Majesty, by Letters Patent under
the Great Seal of Great Britain, bearing date at Westminster, the Fifth day
of February last, gave and granted to the said William Harrison and Peter
Atherton, their executors, administrators, and assigns, His Majestic's especial
licence, full power, sole priveledge and authority, for them, the said William
Harrison and Peter Atherton, their executors, administrators, and assigns, and
every of them, by themselves, or by their deputy or deputies, servants or
agents, or. such others as they, the said William Harrison and Peter Atherton,
their executors, administrators, or assigns, should at any time agree with, and
no others, from time to time, to make, use, exercise, and vend, their method
or Invention of "MAKING SCREWS AND MACHINES FOR DIVIDING OF MATHEMATICAL
INSTRUMENTS FROM THE SAID SCREWS;" within that part of Great Britain called
England, the Dominion of Wales, and the Town of Berwick-upon-Tweed, for

page_text: the term of fourteen years, according to the Statute in that case made and
provided, in such manner as to the said William Harrison and Peter Atherton,
their executors, administrators, and assigns, or any of them, should in their
discretions seem meet, and that they should and lawfully might have and
enjoy the whole profit, benefit, commodity, and advantage, from time to time
arising, by reason of the said Invention, during the said term; to hold, exer-
cise, and enjoy the said licence, powers, priveledges, and advantages, therein
granted unto the said William Harrison and Peter Atherton, their 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 compleat and ended, according to the Statute in such
case made and provided; in which said Letters Patent is contained a proviso,
that if the said William Harrison and Peter Atherton, should not particularly
describe and ascertain the nature of their said Invention, and in what manner
the same is to be performed, by an instrument in writing under their hands
and seals, and cause the same to be enrolled in the High Court of Chancery
within four calendar months next and immediately after the date of the said
Letters Patent, that then the said Letters Patent, and all liberties and
advantages whatsoever thereby granted, should utterly cease, determine, and
become void, as by the said Letters Patent, relation being thereunto had, may
more fully appear.
NOW KNOW YE, that we, the said William Harrison and Peter Atherton,
in pursuance of this said proviso, in the said Letters Patent contained, do
hereby describe and ascertain the nature of the said Invention, and the
manner in which the same is to be performed, as follows, that is to say:-
To make screws perfectly true, and likewise to employ a screw so made for
the dividing streight and curved lines, and thereby render it easy to make a
great number of those mathematical instruments, which are the most essential
to science and navigation, perfect, and for want thereof have been imperfect,
the said screws are to be made is by truly transferring the motion generated
by two planes, inclined towards each other, sliding so as to approach or recede
from each other by an equal motion to a point, cutting a screw upon a cylinder,
moving round its own axis or to the cylinder, letting the point remain at rest;
or when such screw is so truly made, by making another screw from it. The
strait or curved lines are to be truly divided by employing a screw so made to
move a rack, or to be moved thereby, to which the instrument to be divided
being fixed, it will be made to approach or recede from a given point, upon
which a cutter is placed, to a distance equal to one thread of the screw, by
one revolution thereof, and consequently to any fraction of that distance by

page_text: the same fraction of one revolution, which fraction is ascertained by means of
an index.
In witness whereof, the said William Harrison and Peter Atherton
have hereunto set their hands and seals, this Seventh day of March,
in the eighteenth year of the reign of our Sovereign Lord George the
Third, King of Great Britain, France, and Ireland, Defender of the
Faith, and so forth, and in the year of our Lord One thousand seven
hundred and seventy-eight.