Year: 1889

page_text: ALFRED JAMES HOGAN Estate Agent &c. 7 Atlantic Road, Brixton, London, S.W.
do hereby declare the nature of this invention and in what manner the same is to
bo performed, to be particularly described and ascertained in and by the following
statement:-
This invention relates to instruments for the measurement of the circumference of
circles and other figures and surfaces and by a simple calculation arriving at the exact
area contained therein.
In the accompanying drawings is shown marked A the front elevation and B the
side elevation of a measuring instrument constructed according to this invention,
which shows a revolving wheel or disc of brass or other metal accurately fitted upon
steel or other axles which revolve in the cheeks of the leg supporting the measuring
disc or wheel and the said disc is graduated set out or marked accurately showing
12th parts of an inch and 144th parts thereof or more or less as may be desirable or
to any scale and according to the size of the disc or wheel.
The operation is as follows:-the leg being fitted into a pair of compasses or to a
beam compass or other instrument the leg being suitably fitted thereto (in the case of
large circles or other figures I claim the use of a larger disc or revolving wheel
suitably graduated and divided either in feet, inches or parts thereof or by any other
scale) a mark is placed upon say the circumference of any circle and the disc
marked at zero placed thereon and revolved around the said circumference of
the said circle until arriving again back to the starting point or place (to facilitate
the reading or knowledge of the revolutions made by the disc, a small slight spring is
attached to the side of the leg and a pin projecting from the disc at each revolution
causes a slight click thereon)-The full distance travelled by the revolving disc is
divided by 4 and the quotient is inultiplied by itself which will give the exact area of
a circle.
The same rule applies to a segment of a circle or other figure but the disc must be
also run over the chord of a segment or any enclosing lines of any figure and the
measurement recorded must be divided by 4 and then squared as before mentioned to
obtain the required area.

page_text: I also claim that this invention so far as regards the measurement of or graduation
of the dise the shape of the supporting leg the addition of cog whools having teeth
which engage with corresponding teeth on the revolving disc to record the distance
traversod may be modified without departing from the nature of my invention.
Having now fully and particularly described and ascertained the nature of my
said Invention and in what manner the same is to be performed [ declare that
what I claim is :-
First: An instrument for measuring circular figuros-parts of circular figures
and the chords or other enclosing lines thereof and by the simple calculation after-
wards made determining the part area contained therein-the measuring disc or
wheel being arranged to revolve on its axis in a log to be attached to any kind of
compasses or other instrument the said disc being of various sizes and graduations
according to any scale.
Second-An instrument which may bo detached from compassos or other instru-
ment and is applicable by the revolution of its graduate dise to measuring any
curved lines, and having a pin on the disc and slight spring on the leg which
engage with each other at each revolation and record the same by an audible
click.
Third: The calculation of the result in connection with the object specified and
achieved by the use of this instrument is the division of the adineasurement
recorded by the instrument, by 4 and multiplication of the result by itself in
connection with the use of the said invention.
19th February 1889