Year: 1886

page_text: Date of Application, 10th Feb., 1886.
Complete Left, 15th Oct., 1886.
Complete Accepted, 8th Feb., 1887
I, THOMAS DERHAM of 110 St. George's Road, Bolton in the County of Lancaster,
do hereby declare the nature of my said invention to be as follows:-
:―
This invention relates to improvements upon a former Invention for which Letters
Patent were granted to me bearing date the 17th September 1883, No. 4434.
In the construction of hydrometers and saccharometers a series of weights or
poises is usually adopted to extend the range of the instrument and thus avoid the
inconvenience of a long stem.
In order that the stem should possess a constant value and indicate the same
number of degrees of gravity with each successive poise the successive increment to
the total bulk of the instrument should be the bulk of the graduated stem or scale,
and each additional weight should possess a specific gravity bearing a definite relation
to the specific gravities to be indicated by the instrument.
-
By my invention this relation is determined exactly by the following formula :-
Let g
the specific gravity of any poise; G = the initial specific gravity of the
instrument; a= the number of degrees of gravity indicated in the length of the
stem; then
1st.
y = 2G + 2 a
2nd.
3rd.
=
2 G + 3a
2 G+ 4 a
And putting n for the number of repetitions of the scale, then generally nth g =
2G(+1) a.
Its at this invention consists in the annlication of the principle contained
And putting n for the number of repetitions of the scale, then generally th g=
2G(+1) a.
The novelty of this
this invention consists in the annlication of the principle contained
in the foregoing formula, to the construction of the poises of hydrometers, saccharo-
meters, &c, including every variety of construction of the poises, both solid and
hollow, homogeneous and compounded.
EDMUND CHADWICK,
Agent for Applicant.

page_text: substituting the value of a obtained above
Example.
g=G+a+G+ na
G + (n + 1) a
It is desired to construct a hydrometer to indicate specific gravities from 780 to
1.000, employing ten poises, and as many corresponding repetitions of the scale,
exclusive of the first employment of the scale which requires no poise, each range
having a value of 020 of specific gravity, namely from 780 to 800; 800 to 820;
820 to 840, and so on.
Therefore G 780; a =
020; and
=
1.60
1st.
2nd. g
g=
156+04:
-
150+ *06= 1.62
3rd. g=
1.56+08 1.64
4th. g=
1.56 +10= 1.66
5th. 9
= 156 +12 1.68
6th.
= 1:56 +14= 1.70
=
7th. g 1.56 +16=1.72
8th.
1
g 1.56 +18= 1.74
9th. g
10th. g
=
=
1.56.20 = 1.76
1.5622 1.78
The novelty of this invention consists in the application of the principle contained
in the foregoing formula to the construction of the poises of hydrometers, saccharo-
meters, &c., including every variety of construction of the poises, both solid or hollow,
homogenous or compounded, of different materials for modifying their specific gravities.
The essential part of my invention consists in the construction of the poises as above
described, but it is susceptible of the following modification which makes no alteration
in the principle. A definite portion of the receptacle in which the poises are placed
may be detached, and its equivalent added to each of the poises for convenience of
attaching the latter to the instrument, or for increasing the strength and solidity of
each poise when hollow. This addition will then form part of the structure or body
of the poise, and not be loosely added in the interior of the poise merely for the
purpose of adjustment.

page_text: Having now particularly described and ascertained the nature of my said Invention
and in what manner the same is to be performed I declare that what I claim is :-
The principle, substantially as herein described, of constructing the poises of
hydrometers, saccharometers, and other analogous instruments, so that each poise shall
possess a specific gravity bearing a definite relation to the initial specific gravity of
the series of specific gravities to be indicated by the instrument, the same being
determined by the foregoing formula; including also the apparent modifications of the
principle occasioned by detaching a definito portion of the receptacle and adding its
equivalent to each poise.
EDMUND CHADWICK, C.E.,
92. St. George's Road, Bolton,
Agent for Applicant.