Recording the Duration of Sunshine.
Year: 1886

page_text: Recording the Duration of Sunshine.
I, WILLIAM EDWARD WILSON, of Daramona, Streete, Rathowen, in the County
of Westmeath Ireland, Gentleman, 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 :-
Instruments or apparatus according to this invention consist of two portions, one
of which, the indicator, is affected by the sunshine, and the other of which registers
the indications. The former or indicating apparatus is a differential thermometer
so constructed or arranged that one portion of it is exposed to the direct or reflected
rays of the sun, while the other is screened from those rays, or is less sensitive to
them than the first.
As long as the sky is overcast the two parts of the apparatus will be under
similar conditions of temperature and there will be no differential result, but when
the sun shines the portion which is exposed to its rays, or which has been so
treated that it is the more absorbent of radiant heat of the two, will bring the
greater influence to bear on the indicator, which will move. The movement is
made to complete an electric circuit in connexion with the recording apparatus, or
to act upon it directly according to circumstances.
The recording apparatus is provided with a time keeper and may either be a
'totaliser " to shew the number of hours and minutes the sun has been shining, or
has been observed (as the case may be) or may produce a diagram by the rotation
of a paper barrel.
Referring to the accompanying three sheets of illustrative drawings Fig. 1
represents in elevation and part section a differential thermometer in which air is
the medium subjected to expansion. The bulb A is coated with lamp black. The
bulb B is clear-Both bulbs are enclosed in sealed glass globes a. b from which the
air is exhausted. The bulb B is kept in the shade by enclosure in a louvred box,
or by whitening the exhausted globe b. As in the ordinary differential air
thermometer, the two bulbs are united by a tube. This tube contains a thread or
globule of mercury, which is driven backwards and forwards by the differential
expansion of the air in the two globes,

page_text: At a certain part of the tube two platinum wires c. d are fused into the glass.
These wires form part of an electric circuit, and when the thread of mercury touches
them, it forms good electric contact between them, and completes the circuit at
that point.
Fig. 2 shews another arrangement. In this case two ordinary mercurial thermo-
meters with stems of large bore are provided each with a plunger (e. f) these two
plungers being connected by a link g. One of the bulbs is shaded by being
enclosed in a louvred chamber.
With this arrangement a part equi-distant from the points of connexion of the
link with the plungers will not move unless there occurs a difference in the
temperatures of the two thermometers When such difference occurs, the said
equi-distant part of the link will be moved so as to make the required contact.
Such an arrangement may be made to draw a curve of radiation by connecting
the centre of the link at g' to a bar h pivotted at i and provided with a suitable
marker at k.
Instead of air a bi-metallic spring may be employed as the differential medium.
A thermometer constructed according to this modification is shewn in Figs. 3 and 4,
the former being a sectional elevation and the latter a plan.
A. B is a double spiral formed of two metals soldered together. The part A is
exposed to the sun through the glass shade C, while the part B is enclosed in the
box D, the sides of which are perforated to admit of the circulation of air. Double
sides, with perforations breaking joint are used to prevent strong air currents.
E is the pointer or indicator which during sunshine, is caused to come against the
electrical contact F, and complete the circuit at that point.
The recording apparatus shewn in Figs. 5 to 8 produces a permanent record by
a series of dots or marks which are made at every minute, or other determined
interval during the time the sun is shining, on a piece of paper mounted on a
revolving dram. If this paper be ruled with lines representing hours and parts of
hours a chart is obtained shewing exactly at what time the sunshine occurred, and
at what time the sky was overcast.
It is desirable that the paper coiled on the drum should be of a kind which is
susceptible of receiving clear and definite pricks. The paper sold for use with the
"cyclostyle" copying apparatus is a good example of the kind. When the record
is removed from the drum it is used as a stencil or matrix, and copies of it are
produced for reference and distribution by the device of laying it on a sheet of
clean paper and passing an inking roller over it. By placing two sheets of the
paper on the drum and pricking through both, duplicates are obtained, one of which
can be preserved for years and used in conjunction with others taken during corre-
sponding periods, for the purpose of obtaining a general average by a system of
combination printing.
Fig. 5 is an elevation of this form of recording apparatus. Fig. 6 is an elevation
at right angles to Fig. 5 the clockwork being omitted. Fig. 7 is a plan, partly in
section of Fig. 5, and Fig. 8 a plan of Fig. 6.
G is a drum to carry the card or paper. It is mounted on a vertical axis which
is driven by clockwork through the bevil wheels H. H. The upper of these is
connected to the drum axis by a sliding or feather key, so that it may offer
no impediment to the endwise motion of the drum as the screw threaded portion of
the axis turns in the nut I. Thus the drum has both a motion of rotation and of
longitudinal translation, consequently the pointer traces on it a spiral line of dots.
In addition to rotating the drum, the clockwork also brings two electrical contacts
together once a minute. These-form parts of the circuit already referred to in the
thermometric apparatus, and it is only when both sets of contacts are connected at
the same time that the current flows.
The current traverses the coils of the electromagnet K, the armature L of which
carries by means of an extending arm, a marker or pricker M. When the circuit
is complete the magnet attracts its armature and the pricker is forced through the
paper on the drum.
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9

page_text: If only one copy of the chart be wanted the marker may be a pencil or pen, and
then the circuit need only be broken at the thermometer.
When the total time that the sun has shined is the object sought, and not a
record of the distribution of the sunshine during the hours of the day, the drum
and paper are dispensed with, and the magnet operates a counter only. This
counter may be of any ordinary kind, such as Harding's the unit wheel being
turned by a pawl worked by the armature of the magnet. Or the magnet may act
directly on the clock when the circuit is completed at the thermometer, and permit
its balance to oscillate. When the circuit is broken the clock is stopped. When
the indicating and recording apparatus can be placed close together the agency of
electricity can be dispensed with.
In this case the clock may take the form of an ordinary watch movement, by
preference of the verge form. This is kept from working, so long as the sun
does not shine, by a hair or bristle attached to the indicator of the thermometric
apparatus. When the sun shines the hair is drawn back and the watch goes until
sun is again obscured. If this watch be set each evening its reading the next
evening will correspond to the aggregate number of hours minutes and seconds of
sunshine during that day.
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, in instruments for recording the duration of sunshine,
1. The use of a differential thermometer to set recording apparatus in and out of
action either mechanically or electrically.
2. The arrangement or combination of a differential thermometer capable when
affected by sunshine of completing an electric circuit, an electrically moved pointer or
marker, and a constantly moving paper drum or carrier substantially as described.
3. The arrangement or combination of a differential thermometer capable when
affected by sunshine of completing an electric circuit, a clockwork movement which
makes and breaks the same circuit at intervals, and a magnetic counter, the whole
substantially as described.
4. The arrangement or combination of a differential thermometer and a clock-
work movement that is stopped by the thermometer when the sky is obscured, or
vice versa substantially as described.
5. Forming charts or records of sunshine upon paper specially prepared so as to
be easily pierced, (such as cyclostyle paper), substantially in the manner and for
the purposes described.
6. Apparatus constructed arranged and operating substantially as described with
reference respectively to and shewn in Fig. 1, Fig. 2, in Figs. 3 and 4, and in
Figs. 5 to 8 of the drawings for the purposes set forth.
D
1
T
1000