AN IMPROVEMENT IN APPARATUS FOR INDICATING THE HYGRO
Year: 1865

page_text: LETTERS PATENT to William Edson, of Boston, in the County of Suffolk,
in the State of Massachusetts, in the United States of America, for the
Invention of "AN IMPROVEMENT IN APPARATUS FOR INDICATING THE HYGRO-
Sealed the 1st December 1865, and dated the 14th June 1865.
COMPLETE SPECIFICATION filed by the said William Edson at the Office
of the Commissioners of Patents, with his Petition and Declaration, on
the 14th June 1865, pursuant to the 9th Section of the Patent Law
Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
EDSON, of Boston, in the County of Suffolk, in the State of Massachusetts;
in the United States of America, send greeting.
WHEREAS I am in possession of an Invention for "AN IMPROVEMENT IN
APPARATUS FOR INDICATING THE HYGOMETRIC CONDITION OF THE ATMOSPHERE,"
and have petitioned Her Majesty to grant unto me, my executors, adminis-
trators, and assigns, Her Royal Letters Patent for the same, and have made
solemn declaration that I am the true and first Inventor thereof.

page_text: NOW KNOW YE, that I, the said William Edson, do hereby declare that
the following Complete Specification under my hand and seal fully describes
and ascertains the nature of the said Invention, and in what manner the same
is to be performed, in and by the following statement, reference being had to
the accompanying Drawing making a part of this Specification:-
This apparatus is termed a býgrodeik, from hygron, moisture in the air,
and deik (deiko, deiknumi), to show.
The nature of this Invention consists in a combination of pointers attached
to a moveable centre, and employed in connection with a diagram and a
"Mason's hygrometer," or, as it is usually called, "the wet and dry bulb
hygrometer." The object of this Invention is to enable any one by simple
manipulation of the pointers to read upon the diagram of the apparatus the
"relative humidity" and the "dew point" of the air, also the absolute
amount of moisture in the air without the use of tables or calculations.
The following is a description of that form of embodiment of this Invention
which is shown in the Drawing herewith accompanying and making part of
this Specification, which is sufficiently clear and exact to enable others skilled
in the art to practice the Invention. The Drawing shows the apparatus in
front elevation, a being a base, and 6 a standard rising therefrom, both made
of any suitable material and form; c and d are two thermometers, which with
their common scales of degrees are secured to the standard. The bulb of
thermometer c is exposed to the air, that of d is enclosed in a cover of silk or
other suitable material, which by means of filaments and the water shown in
the vessel e is always kept moistened. The apparatus, so far as now described,
constitutes the well-known "Mason's hygrometer," which acts upon the
principle that evaporation cools the body from which it evaporates, and as has
been found by experiment this cooling is in proportion to the rapidity with
which the evaporation proceeds, which again is in proportion to the dryness
of the air in which the evaporation takes place, in other words, the lowering
of the temperature of the covered and moistened bulb is in proportion to the
dryness of the air in which it is placed.
The mechanism which is added to the "Mason's hygrometer," and which
is employed to govern the position of the pointer f, which under manipulations
of the operator, in consonance with the height of the mercury in the thermo-
meters, serves to give upon the diagram marked on the eard or plate g
visual indications of the hygrometric conditions of the atmosphere, is as
follows: There is fixed to the standard 6 a vertical guide piece h, upon
which a slide or carriage i is so fitted that it may be moved easily up and
alown, remaining in any position where placed. In the lower part of the

page_text: slide iis pivoted or journalled the knob j, to and by which the pointer f is
secured. The radius arm k is also fastened to the knob j, and said arm by a
connection or link is connected to another radius arm m of the same length
as is k, which arm m is pivoted to the top of the slide i in the same vertical
centre line with the centre of the knob j. By the pieces q, q, the range of
motion of the pointers is limited in a downward direction to prevent breakage.
The pieces n, n, are springs, which can be adjusted so as to create friction
enough upon the radius arms to hold them where placed; and prevent them
from gravitating. It will now be obvious that by partial turning of the
knob j in one and the other direction the piece will be moved parallel to
piece i, and toward and from it. The pointer o is made fast to the piece / by
means which admit of its adjustment to the mercury column in the thermo-
meter d, so that when the bulbs of both c and d are dry the pointer o can
be adjusted and fixed to the degree on the scale of thermometer d, corre-
sponding to the degree on the scale of thermometer e, agreeing with the top
of its mercury column, it being observed, however, in this adjustment to have
the position of the slide i such that the pointer p, which is permanently fixed
thereto, is in line with the top of the mercury in c. The pointers o and p
being thus relatively adjusted it remains to adjust the pointer f, and then to
construct the diagram on the plate g, which in the Drawing is shown as partly
broken away to disclose the mechanism behind it. Before the diagram is
drawn on the plate g it is a matter of but little moment how the pointer fis
adjusted, except that for convenience, and to have the diagram well located
on the plate g, I prefer to set f at right angles with the radius arms mand k.
After this adjustment the diagram, such as is shown in the Drawing, is easily
projected by the aid of the well-known hygrometric tables. It will be seen
that the pointers o and f are moved with a fixed relation to each other, and
without moving p, by turning the knob j, by which the pointer o is set to the
depression of the mercury caused by the cooling of the bulb of d, consequent
upon evaporation; also that by moving the slide i all the pointers o, f, and p
are moved vertically. The figures on the scales of the thermometers, and on
the right or nearly vertical line of the diagram, indicate degrees of Fahrenheit.
The nearly horizontal curved lines of the diagram correspond to the scale
indicating temperature on the dry bulb thermometer, and are of convenience
in making the diagram. The nearly vertical curved lines are lines of equal
relative humidity, and may be termed isohygrometrical lines, the numbers at
the upper ends of these, or at the top of the diagram, are to be read as per-
centages of moisture, that is, as relative humidity, 100 representing saturation.
The lines running in a generally diagonal direction are dew point lines, the

page_text: numbers at the right of the diagram indicating the dew point of the air. The
number of grains of water in form of vapor contained in a cubic foot of air at
temperature corresponding to the dew point is expressed upon the diagonal
CLAIM.
In combination with wet and dry bulb thermometers a mechanism arranged
to operate substantially as described by manipulation, of which the observer
will indicate to his eye upon a diagram the hygrometric. condition of the
'atmosphere.
WILLIAM EDSON. .(L.S.)