IMPROVEMENTS IN METEOROLOGICAL INDICATING AND AIR-TESTING INSTRUMENTS
Year: 1881

page_text: LETTERS PATENT to Friedrich Hermann Felix Engel, Civil Engineer and
Patent Agent, in the City of Hamburg, Germany, for an Invention of
"IMPROVEMENTS IN METEOROLOGICAL INDICATING AND AIR-TESTING
INSTRUMENTS." A communication from Wilhelm Klinkerfues, Doctor of
Philosophie, Professor and Director of the Royal Observatory at Gottingen,
in the German Empire.
PROVISIONAL SPECIFICATION left by the said Friedrich Hermann Felix
Engel at the Office of the Commissioners of Patents on the 12th May
1881.
FRIEDRICH HERMANN FELIX ENGEL, Civil Engineer and Patent Agent, in the
City of Hamburg, Germany. "IMPROVEMENTS IN METEOROLOGICAL INDICATING
AND AIR-TESTING INSTRUMENTS." A communication from Wilhelm Klinkerfues,
Doctor of Philosophie, Professor and Director of the Royal Observatory at
Gottingen, in the German Empire.
These instruments are constructed to fore-tell or indicate certain dangerous or
damaging meteorological precedences, as night-frost, thunder and lightening, hail
and storm, and they can also be used for sanitary purposes, as the atmospheric air
can by their means be tested upon its percentage of moisture or vapour contained
in it.
The danger of night frost is always present as long as the dew-point temperature
is nearly nil or below that. Likewise experience has shown that a danger of
thunder and lightening is present as soon as the dew point comes near or surmounts
the middle temperature of the season.
This danger, as well as that hail will fall, is under otherwise similar circum-
stances so much the greater the higher the dew-point rises above the middle
temperature of the season.
These new instruments have three scales that show without experiment or
further calculation respectively the dew-point, the relative moisture, and tempera-
ture of the air.

page_text: The construction is based upon the hygroscopic qualities of the human hair and
upon the discovery of the inventor that the shortening of the hair from the
point of saturation is proportional to the decrease of the logarithm of the relative
moisture.
This discovery leads to the following proportion between "Sassure's" degrees of
hygrometer d and percents. of relative moisture p :-
(1) log. p = 0,88470 +0,011153 d.
This, combined with the relation of " magnus " between tension S of the
vapour (in millimeter) and temperature of saturation t (in degrees of
"Celsius") :—
S = 4,525.10
234.69
gives that the variations of
are proportional to the variations of the length of the hair as any two
different tensions S and S¹ stand in proportion of their percentage of relative
moisture
The construction of the instrument may be chosen as follows:-
A hair, or better a hair-string, is fastened at its one end to the outer surface of
a small disc fixed to a horizontal spindle corresponding to the index spindle of a
gauge.
The hair is placed round the disc and tensioned by a small counterweight
fastened to the other free end of the hair. According to the variations of the
length of the hair that depend upon the variations of moisture of the atmosphere
the spindle is turned to either one or other side.
To the axle or shaft of the disc, which is placed in bearings or between points,
two arms are secured, one of which carries at its free end a small thermometer
curved in a segment of a circle and furnished with a common scale. The weight
of the thermometer is counterbalanced by a weight fastened to the other arm that
extends radially from the axle opposite to the arm that carries the thermometer.
An outer circular metal ring fastened to the stand of the instrument carries two
scales, one on the side of the thermometer arm and the other at the side of the
ringleted arm, which latter is at its end formed or furnished with an indicating
hand or point.
,
234,69 + t
The first mentioned scale is divided in degrees of length of 7,4475
and the
end of the thin quicksilver-column of the thermometer, or in other words the
point of temperature of the air indicated by the thermometer, serves as the
indicating hand of this scale.
If the instrument is properly adjusted the end of the thermometer column points
directly to the corresponding dew-point cipher.
The scale on the opposite side of the face of the instrument is divided in
proportions or degrees of log. P, and the indicating hand or point of the second
arm that is likewise influenced in its movements by the variations of the
length of the hair string will directly show to the relative moisture of the
hair.
Instead of making the dew-point scale a fixture the curved thermometer may
form the fixture and the dew-point scale may be attached to the end of the
arm.
By placing this instrument in or upon an aneroid-barometer it can be used for
taking local prognostics of wind and storm.
For sanitary purposes this instrument can be used, as it will show the amount of
.vapour contained in the air.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Friedrich Hermann Felix Engel in the Great Seal Patent Office on
the 12th November 1881.
FRIEDRICH HERMANN FELIX ENGEL, Civil Engineer and Patent Agent, in the
City of Hamburg, Germany. "IMPROVEMENTS IN METEOROLOGICAL INDICATING
AND AIR-TESTING INSTRUMENTS." A communication from Wilhelm Klinkerfues,
Doctor of Philosiphie, Professor and Director at the Royal Observatory at
Gottingen, in the German Empire.
These instruments are constructed to foretell or indicate certain dangerous or
damaging meteorological precedences, as night frost, thunder and lightening, hail
and storm, and they can also be used for sanitary purposes, as the atmospheric air
can by their means be tested upon its percentage of moisture or vapour contained
in it.
The danger of night frost is always present as long as the dew point temperature
is nearly nil or below that. Likewise experience has shown that a danger of
thunder and lightening is present as soon as the dew point comes near or
surmounts the middle temperature of the season. This danger, as well as that hail
will fall, is under otherwise similar circumstances so much the greater the higher
the dew point rises above the middle temperature of the season.
These new instruments have three scales that show without experiment or
further calculation respectively the dew point, the relative moisture, and tempera-
ture of the air.
The construction is based upon the hygroscopic qualities of the human hair,
and upon the descovery of the inventor that the shortening of the hair from the
point of saturation is proportional to the decrease of the logarithm of the relative
moisture.
This discovery leads to the following proportion between "Sassure's" degrees of
hygrometer d and percents. of relative moisture p:-
(1) log. ») = 0.88470 + 0.011153 d.
234,69 +1
any
two
are proportional to the variations of the length of the hair as
different tensions S and S¹ stand in proportion of their percentage of relative
moisture
The construction of the instrument may be carried out as follows and as
illustrated by the accompanying Sheet of Drawings:-
In Fig. 1 of the Drawings a hair, or better a hair-string h, is with its one end
fastened to the circumference of a disc s furnished with an horizontal shaft placed
in bearings or between points of set screws, and this hair string is tensioned by a
small counterweight g or other convenient mechanical means attached to or acting
upon the other free end. To a radial arm extending from the axle or shaft of disc s
a thermometer H is fastened, which latter is formed in curved or circular shape,
and which is furnished with a common scale, and is counterbalanced by a weight b
fastened to an opposite arm or projection of the shaft or axle. The end of the fine
column of quicksilver of the thermometer, or in other words the point t representing

page_text: the temperature of the air, serves at same time as indicating hand to the
corresponding dew-point T of the fixed scale F. Scale F is divided into parts or
7,4475 !
degrees of length of 234,69 +1.
If the instrument has been properly adjusted (which can be attained by
observing the circumstance that in a room of which the air is completely saturated
with vapour or steam the temperature t is equal to T) the end of the thermometer
scale will directly point to the corresponding dew-point cipher T.
Opposite to F another scalo P may be applied to the instrument that is divided
into degrees of log. p, and the indicating band or point of arm b will directly point
to the relative moisture of the air.
Fig. 2 represents a modification in which the thermometer is a fixture and the
dew-point scale F is attached to the movable shaft or axle of disc s.
The scale F
can preferably be made of aluminium to reduce its weight and be used at same
time as a weight or means for tensioning the air. The hand bopposite to F
points in a similar manner, as before described, at scale P to the relative moisture
of the air.
This instrument may also be combined with an aneroid barometer, as represented
by Fig. 2, and a separate hand a moved by the diaphragm of the aneroid points to
the air-pressure, which combination is very convenient for taking local prognostics
of wind and storm.
Having now described the nature and particulars of the said Invention in such
wise that the same may be readily carried into practical effect, I claim,-
The construction of instrument indicating the dew-point, relative moisture, and
air-temperature, simultaneously by the combination of a hygrometric hair or
hair-string h, a thermometer H, and the scales F and P, divided and arranged
substantially as described and as illustrated by the accompanying Sheet of
Drawings.
In witness whereof, I, the said Friedrich Hermann Felix Engel, have
hereunto set my hand and seal, this Seventh day of November, in the
year of our Lord One thousand eight hundred and eighty-one.