EICESTER Apparatus for Facilitating the Calculation of Percentages and for ⚫ some other purposes.
Year: 1891

page_text: Date of Application, 23rd Jan., 1891-Accepted, 28th Feb., 1891
COMPLETE SPECIFICATION,
SEJ
EICESTER
Apparatus for Facilitating the Calculation of Percentages and for
⚫ some other purposes.
I, JAMES BENJAMIN POYNTER, of Wellington, in the Colony of New Zealand,
Accountant, do hereby declare the nature of this invention, and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement and accompanying drawing, that is to say :—
My invention relates to improvements in apparatus for facilitating calculations,
and it has for its objects more especially the calculation of insurance premiums and
rebates, also trade discounts and commissions, and performing multiplication and
division, and other similar calculations with facility and certainty.
In order that my invention may be understood I will proceed to describe the
same, and for that purpose shall refer to the accompanying sheet of drawings, on
which similar letters of reference indicate corresponding parts.
The several parallel and diagonal scales on the drawing shew the position and
division of the several scales for different calculations, being a fac-simile of my
apparatus.
Fig. 2 is a plan shewing the indicating slide.
Fig. 3 is an end view of the same.
Fig. 4 shews a pointer which may be used instead of the slide.
I take a sheet of cardboard, wood, or other suitable material, and on this I form two
scales A. B. and C. D. parallel to one another and at any convenient distance apart. [
then draw a straight diagonal line from A. to C. Now the principle of my invention
depends upon the fact that a straight line oscillating on any point in the diagonal A. C.,
if moved through distances on A. B. that are equal to each other, will measure on C. D.
distances that are also equal to each other; and also if moved through distances on
A. B. that are proportional to each other, will measure distances on C. D. that bear
to each other the same proportion as those on A. B. To carry this principle into
practical effect I divide the scales A. B. & C. D. into convenient and equal parts
(not necessarily the same parts on both scales) and number them respectively from
A. to B. and from C. to D. I then set off the figures on the diagonal by drawing a
straight line from each of the divisions on C. B. to the division 100 on A. B. and
mark the said diagonal on the points of intersection with similar figures to those
on C. D. Now from the construction of my apparatus, a straight line placed across
the three scales and coinciding with any division on A. B. will shew on C. D. what
the number on A. B. will come to at any rate per cent. that is shewn by the
intersection with the diagonal; and this is true wherever the line may be drawn
across the three scales, viz., that it will shew percentages or proportions of hundreds;
but should it be necessary to give the proportions of other numbers (say of years),
I proceed in the same manner as above but draw the straight lines to get the
intersections of the diagonal from the divisions on C. D. to the number 365 instead
of to that marked 100. The scales marked E & F are by the angles at which they
are drawn diagonals of longer parallelograms than A. D. C. B. and are so placed
that by similar operations they indicate the results of higher numbers by means of
the scales and instructions given on the apparatus. In Figs. 2 & 3 is shown a form
of slide (1) placed above the upper scale and sliding on a strip (s) or in any
convenient manner; to this slide is attached a string or line (t) by means of a
projection (r) pointing exactly to the division to be operated on; and in Fig. 4 is
shewn a pointer (p), the point of which can be placed on, or in holes coinciding
with, the divisions to be operated on, and to this pointer is attached a string or
line (t) to draw across the figures in the scales. I prefer a line or fine cord for
convenience, but it is evident that a straight edge of wood or glass or of any

page_text: suitable material may be used for the purpose, provided the positions on the scales
are accurately marked thereby, or a straight edge may be pivoted on a slide
working in a groove along the diagonal.
Having now described the apparatus by which I perform the calculations I will
give a few examples of the practical application of the same.
To calculate insurance premiums:-
Take amount insured on (a) or (b) scale, rate per cent.. on (e) and the premium is
shewn on (c) or (d). If upper scale at top be used, read on upper scale at bottom;
and if lower, on lower scale.
To calculate discounts or commissions:-
Take the premium at the top on (a) or (b) scale, rate in centre on (e), and result
is shewn below at (c) or (d).
To calculate rebates or premiums :-
Find number of days unexpired in the term of policy. Take this number on (a)
scale, pass the line through the scale for proportions of a year at the number
corresponding to premium for whole year, and the amount of rebate is shewn on (c)
scale.
To multiply or use the scales as a ready reckoner :-
Take figures on scale (b) (neglecting the cyphers) as multiplicand, multiplier on
scale (e) and result is shewn on scale (d) and by reversing this process division is
performed.
It will be evident to any arithmetician from this description, and from the
examples given, that my apparatus can be applied to many similar purposes; and
that by making convenient and suitable scales, other calculations resting on a
similar basis may be performed.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed, I wish it to be understood that I
am aware that similar calculations can be made by the use of the sliding rule and
logarithmic scales, but in my apparatus the divisions of the scales for the numbers
to be operated on, and for the result, are equal and regular, thus preventing
confusion, and performing the operation with less liability to mistakes, but I declare
that what I claim is :-
1st. The manufacture of a board, card, or any suitable surface, with scales and
indicating line or rule substantially as described herein and illustrated in the
accompanying drawing.
2nd. The combination of a board, card, or other suitable surface, with scales,
sliding indicator, with line, or marker, substantially as described herein and
illustrated in the accompanying drawing.
3rd. The pointer with wire or cord, as and for the purposes herein described and
illustrated in the accompanying drawing.
4th. The apparatus as and for the purposes substantially as hereinbefore
described.
Dated this 22nd day of Tanu 1901
EDMUND EDWARDS,
35, Southampton Buildings, London, Agent for the Applicant.