IMPROVEMENTS IN METEOROLOGICAL INDICATING AND AIR-TESTING INSTRU- MENTS
Year: 1882

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 INSTRU-
MENTS." ▲ communication to him by Wilhelm Klinkerfues Doctor of
Philosophy, 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 16th June 1882.
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 to him by Wilhelm
Klinkerfues Doctor of Philosophy Professor and Director of the Royal Observatory
at Gottingen in the German Empire.
"
This invention relates to certain improvements in instruments applicable_for
Meteorological and other useful purposes for which Letters Patent were granted to
the present applicant bearing date the twelfth of May 1881 and numbered 2078.
The present Improvements have for their object to simplify the construction and
application of the above named instruments and one of the new modifications is
specially useful for ascertaining the dew-point and relative moisture of the air,
whilst the second modification described hereinafter is an Instrument in which the
indicating hand of the instrument directly shows the dew-point of the momentary
temperature of the atmosphere
The foundation on which the construction of these instrumenta is based is the
same as with the instruments described in the Specification of the aforesaid
Letters Patent No. 2078 of the year 1881 that is to say with respect to the
hygroscopic qualities of the human hair the shortening of the hair from the point
of saturation being proportional to the decrease of logarithm of the relative
moisture. A hand of an instrument to which these bygroscopic alterations of the

page_text: length of a string of hair are transported will consequently describe movements
equal to the logarithm of percentage p of relative moisture for any unit. The
logarithms are indicated on the periphery of a fixed circular scale of the
instrument and these logarithms be marked as p themselves.
On a second movable scale concentric to the former one are marked the
logarithms of the tensions of vapour of the different temperatures of the air and
these marks are indicated as the temperatures themselves. For taking observations
the inner scale is turned or moved by hand as far as required to bring the
momentary temperature of the air in coincidence with the 100 per centic mark
of the fixed scale after which the hand or finger of the instrument will show
or point to the relative moisture on the fixed scale and to the dew-point on the
turnable scale.
The second modification consists of a construction in which the string of hair is
with its one end brought in combination with the moveable end of a thermometer
ring after Bourdon's system, which ring is filled with alcohol guajacol or other
suitable liquid, whilst the other end of the hair-string is connected to a segment
lever fulcrumed on a pin which segment is in gear with a pinion to the axle of
which the indicating hand of the instrument is attached. The movements of the
hand are by this means influenced by the alterations of the hair-string resulting
from the hygroscopic qualities of the latter whilst at same time the movements of
the end of the open thermometer-ring resulting from the changes of temperature
are transmitted to the hand. The length of the hair-string for a corresponding
instrument can be found by measuring the movements of the thermometer-ring
during rising or fall of the temperature of 20 degrees of Celsius and by multiplying
this length of motion by 80.

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 16th December 1882.
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 to me by Wilhelm
Klinkerfues Doctor of Philosophy Professor and Director of the Royal
Observatory at Göttingen in the German Empire.
-
This invention relates to certain improvements in instruments applicable for
meteorological and other useful purposes for which Letters Patent were granted
to the present applicant bearing date the 12th of May 1881 and numbered 2078.
The present improvements have for their object to simplify the construction and
application of the above named instruments and one of the new modifications is
specially useful for ascertaining the dew point and relative moisture of the air
whilst the second modification described hereinafter is an instrument in which the
indicating hand of the instrument directly shows the dew point of the momentary
temperature of the atmosphere.
The foundation on which the construction of these instruments is based is the
same as with the instruments described in the Specification of the aforesaid Lettors
Patent No. 2078 of the year 1881 that is to say with respect to the hygroscopic
qualities of the human hair the shortening of the hair from the point of saturation
being proportional to the decrease of logarithm of the relative moisture.
A hand of an instrument to which these hygroscopic alterations of the length
of a string of hair are transported will consequently describe movements equal to
the logarithm of percentage p of relative moisture for any unit. The logarithms p
are indicated on the periphery of a fixed circular scale of the instrument and
these logarithms will be marked as p themselves.
On a second movable scale concentric to the former one are marked the logarithms
of the tensions of vapour of the different temperatures of the air and these marks
are indicated as the temperatures themselves. For taking observations the inner
scale is turned or moved by hand as far as required to bring the momentary
temperature of the air in coincidence with the 100 per centic mark of the fixed
scale after which the hand or finger of the instrument will show or point to the
relative moisture on the fixed scale and to the dew-point on the turnable scale.
The second modification consists of a construction in which the string of hair is
with its one end brought in combination with the movable end of a thermometer
ring after Bourdon's system which ring is filled with alcohol, guajacol or other
suitable liquid whilst the other end of the hair string is connected to a segment
lever fulcrumed on a pin which segment is in gear with a pinion to the axle of
which the indicating hand of the instrument is attached.
The movements of the hand are by this means influenced by the alterations of
the hair-string resulting from the hygroscopic qualities of the latter whilst at same
time the movements of the end of the open thermometer-ring resulting from the
changes of temperature are transmitted to the hand. The length of the hair-
string for a corresponding instrument can be found by measuring the movements
of the thermometer ring during rising or fall of the temperature of 20 degrees of
Celsius and by multiplying this length of motion by 80.
In order that the said Invention may be fully understood there is annexed
hereto a sheet of drawings wherein Figs 1 and 2 represent the before mentioned
instrument for ascertaining the dew-point as well as the relative moisture of the
air, whilst Figs 3 and 4 represent an instrument constructed in such manner that

page_text: the indicating and on the corresponding stay DOWD LOW L
the air.
With regard to Figs 1 and 2, A is the scale of moisture. B scale of temperature.
The former A is divided in degrees of log p. and B is divided in degrees of log. of
the tensions of vapour of the different temperatures of air.
The hand influenced by the alterations in length of hair string ½ moves
between scales A and B and shows on scale A directly to the relative moisture
of air.
If for example whilst taking an observation the temperaturo bo 20°C and
relative moisture 60° the corresponding dew point is ascertained by turning the
division of scale B marked 20 on to 100% of the outer scale. A the hand will then
show on to 12.5° of the inner scale which is the corresponding dew point.
Or for example if the temperature be 10° C. and the hand shows on to 30%
relative moisture it will be found after turning 10° of the inner scale on to 100%
of the outer scale, + 6-5° C. of the inner scalo as the corresponding dew point.
In Figs. 3 and 4 h represents the hair string one end of which is attached to an
adjustable arm m of the movable end of a Bourdon thermometer ring D, whilst
the other end is attached to an arm n of a segment p that fulcrums on pin r and
that is tensioned by a small weight, a spring or other convenient arrangement.
Segment p is in gear with pinion s to axlo / of which, hands is fastened. C is a
fixed scale and on this the hand z indicates directly the dew point of the
atmosphere.
i and o designate an arrangement for arresting segment p and pinions for the
purpose of transportation of the instrument. By pushing pin o a spring key i
enters between two neighbouring teeth of pinion s and stops the movement of the
aforesaid parts.
Having now described the nature and particulars of the said Invention in such
wise that the same may be readily carried into practice I claim :-
Firstly. An instrument for ascertaining relative moisture and corresponding dew
point of the air, by means of one indicating hand, moved by the alterations in
length of an hygroscopic hair string which hand points or shows to scale A as
well as scale. B divided in degrees constructed and operating as and for the
purpose herein described and in reference to Figs. 1 and 2 of the drawings.
Secondly. The modification in which the free end of a Bourdon thermometrical
ring D, is connected to a hygroscopic hair string in such manner that the hand of
the instrument will by the combined action of the thermometer ring D and
hygroscopic action of string / directly show to the dew point on scale C of the
instrument divided in degrees as and for the purpose herein set forth.
In Witness whereof I the said Friedrich Hermann Felix Engel have herounto
set my hand and seal this eighth day of December in the year of our Lord
one thousand eight hundred and eighty two