CERTAIN IMPROVEMENTS IN MATHEMATICAL, NAUTICAL, OPTICAL, AND ASTRONOMICAL INSTRUMENTS, AND IN THE MODE OF MANUFACTURING DIALS AND OTHER GRADUATED PLATES
Year: 1845

page_text: PIGGOTT'S SPECIFICATION.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM.
PETER PIGGOTT, of No. 11, Wardrobe Place, Doctors Commons, in the City.
of London, Mathematical Instrument Maker, 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 Seventeenth day of April, in the eighth year of Her reign, did, for Herself,
Her heirs and successors, give and grant unto me, the said William Peter
Piggott, Her especial licence, full power, sole privilege and authority, that I,
the said William Peter Piggott, my executors, administraors, and assigns,
and such others as I, the said William Peter Piggott, my executors, adminis-
trators, 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, should.
and lawfully might make, use, exercise, and vend, within England, Wales, and
the Town of Berwick-upon-Tweed, my Invention of "CERTAIN IMPROVEMENTS
IN MATHEMATICAL, NAUTICAL, OPTICAL, AND ASTRONOMICAL INSTRUMENTS, AND IN
THE MODE OF MANUFACTURING DIALS AND OTHER GRADUATED PLATES;" in which
said Letters Patent there is contained a proviso, that I, the said William
Peter Piggott, shall cause a particular description of the nature of my said
Invention, and in what manner the same is to be performed, by an instrument
in writing under my hand and seal, 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.
NOW KNOW YE, that in compliance with the said proviso, I, the said
William Peter Piggott, do hereby declare the nature of my Invention, and the

page_text: manner in which the same is to be performed, are particularly described and
ascertained in and by the following statement thereof, (that is to say):-
These improvements in the construction of mathematical, nautical, optical,
and astronomical instruments, and in the mode of manufacturing dials and
other graduated plates, consist in the application of the electrotype process,
whereby I am enabled to produce certain parts of such instruments, herein-after
described, in a more expeditious and economical manner than by the ordinary
process.
Before describing the particulars of my Invention, it may be well to state
that the present mode of manufacturing or producing graduated plates, such as
those employed or used for barometers, thermometers, quadrants, compass, sun
dials, clocks, and such like instruments requiring plates accurately divided or
graduated, is by the ordinary process of engraving or dividing, or dividing
and engraving, and by which process it is very probable that after having
produced two or more similar plates that on close inspection a material
difference in some of the graduations may be detected, and as it is of great
importance that graduated plates or scales, such as those employed in reducing
and laying down mechanical drawings, and also the scale of chains used for
surveying purposes, together with those already named, should be correctly
divided, and moreover that the several divisions or graduations should in each
and every plate or scale be the same, one to another, it is desirable to employ
some other process than that at present practised, in order that each and every
plate or scale produced may be a perfect fac-simile of the original, which may
be effected by the improvement that constitutes the first part of my Invention,
which is as follows, that is to say:
In order to produce graduated plates such as those already named, I in the
first place prepare a plate of suitable size for the purpose intended, and
engrave upon its surface such graduations and figures or designs as may be
necessary to render the same useful and ornamental. This process, as there is
never but one of each sort required, should be done in the first style of art,
and as correctly as possible, especially as regards the divisions and subdivisions.
Having done this, I next obtain a matrix or mould in a composition of wax,
and from this mould I obtain by means of the electrotype process, which
is well understood, and need not therefore be described, any number of
similar plates in copper or other suitable metal capable of being deposited
by means of the electrotype process. Or, in place of obtaining a mould
in wax or other suitable composition, the same may be made in copper from
the original engraved plate by the aforesaid electrotype process, which will
be more durable, and from which mould almost any number of plates

page_text: may, with care, be obtained. After the plates have been produced in. the
manner herein-before described, I afterwards finish them in the ordinary
manner by silvering, which may also be done by the electrotype process, but I
prefer the ordinary process of silvering as it may be effected with less expence.
It will therefore be observed that by the application of the electrotype process
I obtain the following important result, namely, that each and every plate so
produced must necessarily be fac-similes of the original, and therefore correct, if
proper attention has been paid to the production of the first plate, which I
always preserve for the purpose of obtaining the mould or moulds from which
I afterwards obtain the plates, in the manner and for the purpose herein-before
described; and I may here add, that by this mode of manufacturing dials and
other graduated plates, the same may be produced at considerable less expence
and more correct than by the mode hitherto practised of engraving or dividing,
or dividing and engraving.
Having thus described the first part of my Invention, and the manner. in
which the same is to be performed, I would have it understood that I lay no
claim to any part of the apparatus known by the name of voltaic or galvanic
battery, neither do I claim the electrotype process unless the same be employed
for the purpose herein-before described; but what I claim with regard to this the
first part of my Invention is, the production of graduated plates for mathematical,
nautical, optical, and astronomical instruments by means of the electrotype
process, instead of the ordinary process of engraving or dividing, as heretofore.
The second part of my Invention, which relates to improvements in mathe-
matical, nautical, optical, and astronomical instruments, consists in a new mode
of manufacturing the compass box or case containing the magnetic needle.
I would also observe with regard to this part of my Invention, that the
objections to the present mode of manufacturing compass boxes or cases
containing the magnetic needle arise from local attraction, caused in most
cases by small particles of iron, which in the present mode of casting or
manufacturing such boxes become amalgamated and unequally distributed,
which have the effect of causing a variation in the needle. In some instances
I have observed the needle to vary from one to four or more degrees in
consequence of small particles of iron having been contained in the metal
from which the compass box or case has been constructed. Under such
circumstances it is necessary to drill a small hole or holes in that part of the
case supposed to contain the particle or particles of iron, in order to remove
the same, which hole or holes are afterwards to be plugged up and finished off
so as to form a perfect box or case. The object of this part of my Invention
is, therefore, to obviate the above process, which is not only expensive but
シ

page_text: attended with uncertainty, by the application of the electrotype process,
whereby, I am enabled to obtain a compass box or case of pure and unalloyed
metal, free from any particles which may have a tendency to attract the
magnetic needle. These boxes or cases I produce by the electrotype process
in the following manner, that is, I prepare a mould of the required size of
wax or other suitable composition, and deposit upon it, by means of the
electrotype process, copper or other suitable metal capable of being deposited,
until I have obtained the required strength and thickness, which case is after-
wards to be finished in the ordinary manner of making such cases, or otherwise.
I would here remark, that I sometimes make such cases by first depositing
pure copper in the form of a sheet or block, and afterwards work the same
into the form required; my object being to obtain a compass box or case of
metal free from any magnetic attraction, which I do in the manner herein-
before described.
Having thus described the nature of my Invention, and the manner in which
the same is to be performed, I would have it understood that I do not confine
myself to the precise details herein mentioned so long as the peculiar character
of my Invention be retained; but what I claim as my Invention is, the
application of the electrotype process for the purpose of producing certain
parts of mathematical, nautical, optical, and astronomical instruments, as
herein-before described.
In witness whereof, I, the said William Peter Piggott, have hereunto set
my hand and seal, this Seventeenth day of October, in the year of our
Lord One thousand eight hundred and forty-five.
WILLIAM PETER (L.S.) PIGGOTT.
AND BE IT REMEMBERED, that on the Seventeenth day of October, in
the ninth year of the reign of Her Majesty Queen Victoria, the said William
Peter Piggott came before our said Lady the Queen in Her Chancery, and
acknowledged the instrument aforesaid, and all. and every thing therein
contained and specified, in form above written. And also the instrument
aforesaid was stamped according to the tenor of the Statute made in the fifty-
fifth year of the reign of His late Majesty King George the Third.
Inrolled the Seventeenth day of October, One thousand eight hundred
and forty-five.