IMPROVEMENTS IN APPARATUS OR INSTRU- $ MENTS KNOWN AS RADIOGRAPHS.
Year: 1879

page_text: LETTERS PATENT to Clara Milton, of South Audley Street, in the County of
Middlesex, for the Invention of "IMPROVEMENTS IN APPARATUS OR INSTRU-
$
MENTS KNOWN AS RADIOGRAPHS.'" A communication from abroad by David
Winstanley, of Paris, in the Republic of France.
Sealed the 6th February 1880, and dated the 12th August 1879.
PROVISIONAL SPECIFICATION left by the said Clara Milton at the Office of
the Commissioners of Patents on the 12th August 1879.
" "
CLARA MILTON, of, South Audley Street, in the County of Middlesex.
"IM-
PROVEMENTS IN APPARATUS OR INSTRUMENTS KNOWN AS RADIOGRAPHS.' (A
communication from abroad by David Winstanley, of Paris, in the Republic of
France.)
$6
This Invention relates to certain improvements in apparatus or instruments
known as radiographs," with the objects which are rendered apparent in the
following description:-
The "radiograph" is an instrument used for automatically recording the duration
of the sunshine, and has hitherto been constructed in such a manner that a spherical
lens provided for that purpose burns a sheet of paper when the sun shines, and thus
makes a record of the phenomenon.
These improvements consist essentially in the application of the differential
thermometer, or of difference thermometers to certain other appliances in order to
obtain an automatic registration of the duration and intensity of sunshine.
">
According to the first improvement, which has for its object the obtaining of a
record merely of the duration of the sunshine, a "differential thermometer is
attached to a scale beam or its mechanical equivalent, and the arrangement is so
adjusted as to permit one end of the beam to press gently upon a support. The
other end of the beam carries a lead pencil or other marking instrument, the point
of which is almost in contact with a sheet of paper intended for the reception of
the record, and which is moved at a suitable speed by an arrangement of clock-
work.
The tube, connecting the bulbs of the differential thermometer contains a liquid
intended to act by its gravity. This liquid in the normal condition of the apparatus

page_text: does not reach so far as the bulb at the pencil end of the beam, but extends
preferably as far as the other bulb at the other end of the beam. It is preferred
to use mercury in conjunction with sulphuric acid as the material of this liquid
column, because of the weight of the mercury and because of the facility with which
it moves in a tube already moistened with sulphuric acid.
The bulb at the supported end of the beam is so circumstanced that it becomes
of a higher temperature than the other bulb when the instrument is exposed to the
operation of radiant heat, and this is accomplished preferably by the simple
expedient of painting it black, though of course the same result may be obtained by
using a shade wherewith to cover the other bulb.
When the instrument is used it is placed in a position in which the sunshine
shall have free access to it, and preferably with the line or tube connecting the
bulbs in the plane of the meridian of the place, with the bulb at the supported end
of the beam to the south.
When the sun shines the air enclosed in the bulb at the supported end of the
beam becomes of more elevated temperature than that enclosed in the other bulb,
and by its increased tension moves the liquid column in the horizontal tube away
from it towards the other bulb. The adjustment of the balance is thereby destroyed
and the weight becomes placed upon the pencil point, which then commences a record
of the duration of the sunshine upon the paper moved by the clockwork. When
the sun has ceased to shine the bulbs speedily become of equal temperature, the
air in the blackened bulb contracting, upon which the liquid column returns to its
original position and removes the pencil point from the paper sheet beneath, upon
which there is consequently no further record made until the next depression of the
pencil.
An interval of time of course elapses after the instrument is first exposed to the
operation of the solar rays before the pencil is thus actuated. This interval naturally
diminishes with the size and thickness of the bulbs. As the amount of fluid capable
of movement in the horizontal tube also diminishes with these conditions, and there-
with the amount of pressure on the pencil point, it becomes desirable when great
sensibility is required to employ some special mechanical appliance to give motion
and pressure to the pencil, and to utilise the beam arrangement, or at any rate the
thermometer thereof, merely to start and stop this special mechanical appliance
which in reality is to do the work.
There are two forms of special mechanical appliances which the inventor of the
present improvements has devised to meet this end, the one a clockwork arrange-
ment, and the other an apparatus actuated by electro-magnetism. The former
may be employed in conjunction with the beam arrangement or its equivalent for
its actuation, whilst the latter (which has several advantages) requires the
thermometer alone.
The clockwork appliance consists of a train of wheels actuated preferably by a
spring and regulated by a "fly." One of the spindles of the clockwork is con-
nected with a wheel or crank by which the pencil is raised and lowered, and a
light spring is so located as to induce at the proper portion of the stroke the
pressure needed on the pencil point. This spindle also carries a wheel notched on
one portion of its circumference, and intended by the position of this notch to
determine the position of the pencil point. A balanced bar having (for sensibility
of movement) its centre of gravity very nearly coincident with its centre of sus-
pension is used to arrest the motion of the regulating "fly" and to permit it to be
resumed. This bar is furnished with two projections which are intended to
alternately enter the notch of the wheel described, one of them when the pencil is
in contact with the recording sheet, the other when it is not. When neither of
these projections is in the notch the fly is unimpeded and the clockwork moves,
but when the notch is occupied by either, the termination of the bar comes in contact
with the fly and arrests the motion of the wheelwork.
The bar in its normal position is so adjusted as to exert a slight pressure upon
that projection which enters the notch when the pencil is out of contact with the

page_text: record paper placed beneath, and the beam arrangement alters this adjustinent
when the sun shines, and by bringing the pressure on the opposite projection
liberates the mechanism until the pencil is in contact with the paper, when the
motion is again arrested and the process of recording is commenced. By
adopting this arrangement it will be seen that the pencil can be brought into
contact with the paper with a force as large as is desired by means of one as small
as may be chosen, thus conferring upon the instrument any degree of delicacy
which may be required.
The electro-magnetic arrangement above referred to consists firstly of a bar
pivoted or hinged at one end, and carrying the pencil holder at the other. Beneath
it is another bar connected with the first one by a spring. Another spring presses
the first bar upwards and the tension of these springs is so adjusted that in the
normal condition of the apparatus the pencil point is out of contact with the
recording sheet beneath. An electro-magnet is placed beneath the second bar to
which latter the keeper of the magnet is attached. When this magnet is rendered
active by an electric current the lower bar descends, the spring connecting it with
the other bar is subjected to tension and the pencil is brought with pressure into
contact with the sheet beneath. The lower bar is then secured in its fresh position
by a pivoted bolt which can now be drawn into the requisite position by a spring.
This bolt at the same time breaks contact with the battery and thereby preventing
a needless expenditure of electric power.
The bolt however carries the keeper of a second magnet, and when this magnet
is actuated by an electric current the bolt is withdrawn against the tension of its
spring, both bars fly upwards and the pencil is no longer in contact with the sheet
beneath. But in their motion upwards the electric contact is once more broken by
the arrangement seen on the left hand portion of the upright column, thereby for
the second time preventing a useless expenditure of electric power.
When the electro-magnetic apparatus is employed the differential thermometer
above described is used merely to give electric contacts, and may obviously be
stationed at any convenient distance from the pencil holding apparatus and from
the clock which carries the record sheet, a circumstance which has the obvious
advantage of enabling these pieces of mechanism to be placed in a warm appart-
ment or other locality where they will be effectually protected from any detrimental
influences of the weather. The differential thermometer in this case has three
platinum wires hermetically inserted in its stem so that they may be brought into
electric contact with the mercury within. The central one is permanently in contact
with the mercury and with one pole of the galvanic battery employed, whilst the other
wires are connected, that near the shaded or equivalent bulb with the magnet firstly
mentioned, and that from near the blackened or equivalent bulb with the magnet
secondly mentioned, and each one thence through its especial contact breaker with
the other pole of the battery used. In the normal condition of this arrangement
the wire near the blackened bulb is immersed in the mercury contained in the tube
of the thermometer, and during the continuance of this normal state would, but for
the contact breaker connected with that magnet, maintain complete the battery
circuit. During the normal condition of the arrangement the other wire is out of
contact with the mercury within the tube. When the sun shines upon the dif-
ferential thermometer portion of the apparatus the mercury is moved from the wire
near the blackened bulb to that near the other bulb. The circuit is now complete,
the magnet firstly mentioned comes into operation, the pencil is drawn down with
pressure on the record sheet and is bolted in its place. The contact with the
battery is broken, its electricity ceases to be consumed, and the record of the sun-
shine is commenced. When the sun has ceased to shine the blackened bulb cools,
the mercury returns, the contact at the other end is broken, and that at the
blackened bulb end made. The magnet secondly mentioned then comes into active
operation, the bolt which retains the pencil in contact with the paper is withdrawn,
the pencil is raised, the contact is broken, the expenditure of battery power again
is stopped, and the production of the record ceases. Of course, in this case the

page_text: mercury in the tube of the thermometer is used without sulphuric acid as that body
would be decomposed by the electric current.
In order to effect the automatic registration of both the duration and intensity
of sunshine the inventor proceeds as follows:-Upon a wheel delicately poised upon
its central point is affixed a differential thermometer, of which the tube is circularly
curved concentric with the wheel, which, apart from the mercury occupying the
lower portion of the bend of the tube, is accurately counterpoised. When the sun
shines upon the instrument and effects an increase of tension in the air, contained
within the blackened bulb the wheel partially rotates to an extent varying with
the intensity of the solar rays. By means of a cord in a groove cut in the periphery
of the wheel this motion is communicated to any suitable one of those appliances
now in use for giving motion to a pencil in a direction at right angles with that of
the record sheet, and there is thus obtained in the usual diagrammatical form an
automatic lead pencil record of both the duration and the intensity of the sunshine.
It is preferred to use this wheel arrangement instead of the scale beam hereinbefore
described, even for those purposes in which it is desired merely to record the
duration of the sunshine, as there is in this case none of that rushing of the fluid
experienced in the horizontal tube, and which is somewhat difficult so effectually to
overcome as to offer no obstacle to the free vibration of the balance.
Although the inventor prefers to adopt the lead pencil method of recording
sunshine, still he does not limit himself thereto, as the differential thermometer is
no less applicable to the photographic mode of recording. In order to make an
automatic record of the duration and intensity of sunshine by the photographic
method the inventor uses a differential thermometer, with its tube in a vertical
position, and preferably bent into a U shape so as to bring both bulbs into
proximity, and he also prefers to have the thermometer made of glass, and one bulb
clear and the other blackened, as hereinbefore described. He also prefers to use a
flattened tube for reasons which will be obvious. Into this tube is introduced
some fluid rendered opaque, at any rate to such rays as affect the photographic
paper employed. It is of little consequence what fluid is employed, though blackened
sulphuric acid is used by preference on account of its facility of movement and the
fact that its boiling point is much higher than any temperature to which it is likely
the instrument will be exposed. The cylinder carrying the photographic sheet
destined for the reception of the record is actuated by clockwork, and enclosed
within a box. In front of this cylinder is a slit, opposite to which, on the outer
side is the vertical tube of the thermometer containing the fluid intended to
intercept the passage of those rays which influence the photographic paper
employed. The apparatus is so adjusted that when both bulbs are of equal
temperature daylight is quite excluded, or preferably that it has access to a small
space only below the zero line of the record sheet. The record sheets are impressed
with lines in both directions from a negative previously prepared to suit the instru-
ment, which lines indicate in one direction differences in time, and in the other
differences in temperature. The application of this instrument is obvious; when
the sun shines a difference of temperature ensues between the air contained in
one bulb, and that within the other. The darkened liquid column is elevated (or
depressed accordingly as arranged), and the light entering the slit records upon
the photographic sheet the fact of sunshine, and also its intensity by the position
of its terminus. Of course the same effect may be obtained if two ordinary liquid
thermométera are employed in conjunction with clockwork and a photographic
sheet if they are so arranged as to indicate different temperatures in sunshine,
and the same temperature in the shade, and this may obviously be effected by
the means already named as applying to the bulbs of the differential thermometer.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Clara Milton in the Great Seal Patent Office on the 12th
February 1880.
"IM-
CLARA MILTON, of South Audley Street, in the County of Middlesex.
PROVEMENTS IN APPARATUS OR INSTRUMENTS KNOWN AS "RADIOGRAPHS.'" (A
communication from abroad by David Winstanley, of Paris, in the Republic of
France.)
This Invention relates to certain improvements in apparatus or instruments
known as "radiographs," the objects of the improvements being rendered apparent
in the following description thereof :-
"Radiographs" consist of a class of instruments employed in physical research for
automatically recording the duration and intensity of sunshine, or the duration,
intensity, and quantity of other thermal radiant energy to which they may be
exposed.
In the arrangement which has been most generally used for obtaining such a
record a spherical lens of glass is so disposed as to burn a piece of wood or paper by
the concentration of the sun's rays when it shines.
The present improvements consist essentially in the application of the "differential-
thermometer," or of difference-thermometers, to certain other appliances, in order to
obtain a record of radiance such as is herein before referred to.
According to, the first of the present improvements, which has for its object the
obtaining of a record of the duration merely of the thermal radiant energy, from
whatever source it may be derived, though the measurement of the radiant energy
of the sun is the chief use to which radiographs are put. A "differential thermo-
meter" 1 is attached to a scale beam 2, or to its mechanical equivalent, in the
manner illustrated in the side elevation, Figure 1 of the accompanying Drawings,
and the arrangement is so adjusted as to permit one end of the beam to rest lightly
on a support 3. The other end of the beam carries a lead pencil or other marking.
instrument 4, the point of which is almost in contact with a sheet of paper intended
for the reception of the record, the paper resting on a disc 5 or on any equivalent
surface, such as a cylinder, and being moved at a suitable speed by an arrangement
of clockwork 6. The tube 7 connecting the bulbs 8, 9, of the thermometer contains
a liquid intended to operate by its weight, mercury being the substance which is
preferred because of its superior weight, a small amount of sulphuric acid being also
used in conjunction therewith to facilitate the movement thereof.
When a horizontal tube 7 is used, as in the present illustration, the liquid it con-
tains does not, in the normal condition of the instrument, reach so far as to come
beneath the bulb at the pencil end of the bean, a space being left there for its
motion, but it does by preference reach quite to beneath the bulb at the supported
end of the beam, so as to give the greatest mechanical effect.
The bulb 8 at the supported end of the beam is so circumstanced that it becomes
of a higher temperature than the other bulb 9 when the instrument is exposed to
radiant heat, and this is accomplished preferably by the simple expedient of making
it black, after the manner adopted in the construction of "solar radiation thermo-
meters" and similar instruments, though of course the same result may be obtained
by shading the bulb 9 from the influence of thermal radiance.
When the instrument is used, the radiant heat to which it is exposed being more
freely absorbed by the (blackened) bulb 8 than by the (clear or silvered) bulb 9, the
air contained within the former is expanded, and thus causes the liquid column to be
moved along the tube 7 towards the bulb 9; the adjustment of the balance is thereby
destroyed in such a manner as to cause the pencil-end of the beam to be depressed,
the pencil then bearing upon the moving sheet of paper beneath, and making a
record-line thereon, the positions of the termination thereof determining the dura
tion of the thermal influence, or of the instrument's exposure thereto. When the
....

page_text: radiance is cut off (as, for instance, by the passage of a cloud, if the sunshine be its
source) the bulbs speedily become of equal temperature, thereby equalizing the
tension of their contained air and allowing of the instrument resuming its former or
normal position, the mercury returning to its original position, again tilting the
beam 2, so as to raise the pencil 4 and stop the production of the record, until by a
fresh exposure to thermal influence these operations are all again reversed.
An interval of time of course elapses after the exposure of the instrument to the
influence of the radiance it is intended to record before the pencil is actuated in the
way just described. This interval naturally diminishes with the size and thickness
of the bulbs, but so does the weight of the liquid moved, and with it the pressure
available on the pencil point; it becomes desirable, therefore, where great sensibility
is required, to employ some auxiliary mechanism to actuate the pencil, using the
beam arrangement or its equivalent, or at any rate the thermometer thereof, merely
to start and stop this auxiliary mechanism, which in reality is to do the work.
There are two forms of auxiliary mechanism which the inventor of the present
improvements has devised to meet this end; the one is an arrangement of clock-
work, and the other an apparatus actuated by electro-magnetism. The former
requires the beam arrangement or its equivalent for its actuation, but the latter
requires the thermometer alone.
The clockwork arrangement is illustrated in side elevation of its opposite sides in
Figures 2 and 3, and is shewn as consisting of a train of wheels 10, actuated prefer-
ably by a spring and regulated by a "fly "11. One of the spindles of the clock-
work carries a wheel or crank 12, which by operating through the intervention of
a connecting rod 13 upon a lever 14 causes the raising or lowering of the pencil 4,
a light spring 15 being so located as to induce, at the proper portion of the stroke,
the needful pressure on the pencil-point. The same spindle also carries, but at its
opposite end, a wheel 16 which is circumferentially notched at 17, and the position
of which notch determines the position of the pencil-point. A balanced bar 18,
having (for sensibility of movement) its centre of gravity very nearly coincident
with the point 19 on which it turns, is used to arrest the motion of the regulating
"fly" 11, and to permit it to be resumed. This bar is furnished with two projec-
tions 20, 21, which are intended to alternately enter the notch 17 of the wheel 16,
one (20) of them when the pencil is in contact with the record-sheet, and the other
(21) when it is not. When neither of the projections is in the notch the fly is
unimpeded and the clockwork moves, but when the notch is occupied by either a
pin on the termination 22 of the bar 18 comes in contact with the "fly" and arrests
the motion of the wheelwork.
The bar 18, in its normal position, is so adjusted as to exert a slight pressure of
the projection 21 against the edge of the wheel 16, so as to cause it to enter the
notch 17 when opposite thereto, and the beam arrangement alters this adjustment
under the influence of the sun-shine (or other form of radiant heat), and by bringing
the pressure on the other projection 20 liberates the clockwork mechanism until the
pencil is again in contact with the paper, when the motion is again arrested by the
projection 20 entering the notch 17, when the process of recording is commenced.
23 represents a string connecting the supported end of the beam 2, which rises
under the influence of thermal radiance with the bar 18; and 24 represents
adjustable counterpoises to effect any adjustment which may be required.
By adopting this arrangement it will be seen that the pencil can be brought
into contact with the paper with as great a force as is desired by means of one as
small as may be chosen, thus conferring upon the instrument any degree of delicacy
which may be required.
The electro-magnetic arrangement above referred to is illustrated in side elevation
in Figure 4, and in it the pencil 4 is shewn as carried by a bar 25, pivoted or
hinged at its opposite extremity to a suitable support 26. Beneath this bar is
arranged another bar 27 likewise pivoted to the support 26. These bars are
connected by a spring 28, which has a constant tendency to draw them together, the
bar.25 being likewise acted upon by another spring 29 bearing upon a support 30,

page_text: and which constantly presses it upwards, the tension of these springs being. so
adjusted that in the normal condition of the apparatus the pencil-point is kept out
of contact with the record-sheet beneath. An electro-magnet 31 is placed beneath
the bar 27, to which latter the keeper 32 of the magnet is attached. When this
magnet is rendered active by an electric-current, the bar 27 is attracted downwards,
and the spring 28 connecting it with the bar 25 being thus subjected to tension
causes the pencil 4 to be brought down with pressure into contact with the record-
sheet. The bar 27 is then secured in its fresh position by a pivoted locking-bolt 33,
which can now be drawn into the requisite position by a spring 34, the bolt at the
same time, by means of the arrangement 56, breaking contact with the galvanic-
battery 35 employed, thereby preventing a needless expenditure of electric power.
The bolt 33. however, carries the keeper 36 of a second magnet 37, and when this
is actuated by an electric current the bolt is withdrawn against the tension of its
spring 34, both bars fly upwards and lift the pencil from the paper; but in their
motion upwards the electric contact is once more broken by the arrangement 38
carried by the support 30, thereby for the second time preventing a useless expen-
diture of electric power.
"
The above referred to contact-breaker 56 consists of springs which normally press
against each other and so conduct the electric current, but which are separated by
the pointed projection carried by the spring 34, when it shoots the bolt. The
contact-breaker 38 is essentially the same.
When the above described electro-magnetic apparatus is employed the
differential-thermometer" 1 is used merely to give electric contacts, and may
obviously be stationed at any convenient distance from the pencil actuating.
apparatus, which, with the clockwork which advances the record-sheet, may be
placed in a warm apartment, where they will be most effectually protected from the
influence of the weather.
In this application the differential thermometer 1 has three platinum wires
39, 40, 41, hermetically inserted into its tube 7 so that they may be brought into
electric contact with the mercury within. The central wire 39 is permanently in
contact with the mercury, and with one pole 42 of the battery 35, whilst the other
wires are connected, that (40) from near the shaded or unblackened bulb 9 with the
magnet 31, and that (41) from near the blackened or more exposed bulb 8 with the
magnet 37, and each one thence through its especial contact-breaker with the other
pole 43 of the battery used.
In the normal condition of this arrangement the wire 41 is immersed in the
mercury contained in the tube 7, and during the continuance of this normal state
would, but for the contact-breaker 38, connected with the magnet 37, maintain
complete the battery circuit, the wire 40 not being in contact with the mercury
during this normal condition of the apparatus.
When the sun shines upon the differential thermometer part of the apparatus,
or when that portion of the apparatus is exposed to the operation of some other
thermal radiance, the mercury is moved from contact with the wire 41 into contact
with the wire 40. The circuit is now complete, the magnet 31 is excited, the pencil
is drawn down with-pressure upon the moving record-paper, and is bolted in its
place, the contact with the battery 35 is broken, its electricity ceases to be con-
sumed, and the record of the solar, or other radiance, is commenced.
When the sun has ceased to shine the bulb 8 cools, the mercury returns into
contact with the wire 41, and out of contact with the wire 40, the magnet 37 then
becomes excited, the retaining bolt 33 is withdrawn, the pencil 4 is raised, the
contact is broken, the expenditure of battery-power is again stopped, and the
production of the record ceases.
It will of course be understood that in this application the mercury in the tube
of the thermometer is used without sulphuric acid, as the latter would be decom-
posed by the electric current.
In so far as now described these improvements relate, as above indicated, to means
of recording only the duration of thermal radiance. .
.

page_text: In order to effect the automatic registration of both the duration and intensity as
well, the inventor proceeds as follows, reference now being had to the side elevation,
Figure 5.
A differential thermometer 1, of which the stem 7 is circularly curved, is mounted
concentrically upon a wheel 44 (or its equivalent) which in turn is delicately
balanced in a vertical position upon its central point 45. The tube 7 is partly
filled (preferably through about half its curve) with mercury, a little sulphuric acid
being also introduced for the reason herein before stated. The bulb 8 is blackened,
and the other one 9 is silvered or left clear. When exposed to sunshine or other
source of radiant heat, the air contained within the bulb 8 expands, and by
producing a partial rotation of the wheel 44 indicates by the angular position of
one or other of its radii, the intensity of the thermal radiance to which it is
exposed.
In order that the variations in this radiance may be automatically recorded, the
wheel 44 may be connected by a cord or otherwise with one or other of the
registering appliances now in use, in conjunction with other meteorological instru-
ments. The inventor however prefers to use the arrangement illustrated in
Figure 5, in which one 46 of the radii of the wheel is prolonged in the form of a
needle; the point of which makes tracings on a cylinder 47 covered with smoked
paper, after the manner so extensively employed in the large observatories of
France for recording the readings of other instruments. This cylinder is slowly
rotated by the arrangement of clockwork 6, and by these means the inventor
obtains in the usual diagrammatical form an automatic record of both the duration
and the intensity of the thermal influence. Figure 5 does not illustrate the normal
position of the apparatus, but its medium position between no radiance and the
maximum expected. The zero line is at one extremity of the cylinder (depending
upon which bulb is blackened), and the absence of radiation is indicated when the
needle reaches that; 57 represents movable weights by which the centre of
gravity of the wheel may be adjusted; and 58 is a counterpoise to the weight of
the tracing needle.
When the radiograph is intended to be frequently removed from place to place,
the inventor constructs it as illustrated in the side elevation, Figure 6, by con-
necting two separate air thermometers 48 (or liquid thermometers where slower
indications are required) with two metallic or other boxes 49, having elastic and
corrugated faces 50 (like the boxes enclosed in aneroid barometers) opposite to
each other and connected by a bar 51. Obviously the temperature and the pres-
sure of the contained air (or liquid) will cause no motion of the bar 51 if the bulbs
of both thermometers 48 and both the boxes 49 have a similar construction, but
any difference in the power of absorption of the heat applied to the bulbs caused
by treating them in the manner hereinbefore mentioned, causes a motion of the
bar 51 and of the needle 46 which is centred at 52 upon the record-sheet carried
by the slowly revolving cylinder 47, so that the arrangement is in reality a true
differential thermometer, the indications of which are, if the arrangement be well
balanced, unaffected by its position.
Although the inventor prefers to use lead-pencil or tracing methods for recording
thermal radiance, he does not bind himself to use them, as the differential ther-
mometer is equally applicable to the photographic method of recording.
In order to apply this methed to the registration of thermal radiance, the
inventor uses a differential thermometer 1 with its tube 7 in a vertical position,
and preferably bent into a U-shape, so as to bring both bulbs into proximity, as
indicated in the front and side elevations Figures 7 and 8, and he also prefers to
have the thermometer made of glass with one bulb 8 blackened, and the other
one 9 silvered or left clear as and for the purposes hereinbefore described; be also
prefers that the tube 7 shall be flattened for reasons which will be obvious, and
into this tube be introduces some suitable fluid rendered opaque, at any rate to
such rays as affect the photographic paper used. Colored sulphuric acid is the
liquid the inventor prefers to use (though it is not the only one which is suitable); -

page_text: the coloring being effected by the admixture of some carbonaceous matter with the
acid before it is enclosed within the tube. The cylinder 47 carrying the photo-
graphic sheet destined for the reception of the record is actuated by clockwork (6)
as in the previous examples, and is enclosed within a box 53. In front of the
cylinder 47 a slit is made in the box 53, and opposite the slit on the outer side of
the box is arranged the vertical tube 7 of the thermometer containing the light-
intercepting fluid.
This apparatus is so adjusted that when both bulbs 8, 9, are at an equal tem-
perature, daylight is quite excluded, or preferably, that it has access to a small
space only below the zero line of the record-sheet, so that it may mark a zero-
line.
The application of the instrument in this form is obvious. When subjected to
the influence of thermal-radiance, such, for instance, as sunshine, a difference of
temperature between the bulbs 8, 9, ensues, and the darkened liquid column is
depressed (or elevated accordingly as arranged), and the light entering by the slit
records the fact of sunshine by a line or marking, the vertical termination of
which shows by its position the intensity as well.
Of course the same effect may be obtained if two ordinary liquid thermometers
are employed in conjunction with clockwork, and a photographic sheet if they are
so arranged as to indicate different temperatures in the sunshine, and the same
temperature in the shade such as by the means hereinbefore described.
The record sheets intended for employment by the photographic method are
preferably impressed with lines both horizontally and transversely from a negative
previously prepared to suit the instrument to which they are to be applied, the
transverse lines indicating differences of time, and the longitudinal lines differences
of temperature.
In the beam or wheel arrangements herein before described and illustrated in
Figures 1 and 5, two thermometers may be substituted for the one differential
thermometer described, and with advantage in some cases, provided these ther-
mometers do not consist of bulbs containing air, and the stems of which dip into
liquids held in cups below, such an arrangement would be inadmissible, inasmuch
as the results obtained thereby would be (though not obviously) confused by the
thermal and barometric conditions of the outer air. The inventor of the present
improvements therefore claims the use of two liquid thermometers connected with
a bean or its equivalent in such a way as to cause its inclinations to vary with the
differences of temperature experienced in the bulbs, and this may be effected either
by the suspension of these thermometers, one from each of the extremities of the
beam, their tubes dipping into cups beneath; or (and preferably) by such an
arrangement as is illustrated in the side elevation, Figure 9, in which two liquid
thermometers 54 are mounted on a scale bean 2, the tubes 7 terininating in the
usual bulbs 8, 9, (which are for the present purpose, the one blackened and the
other silvered) at one extremity, and at the other in reservoirs 55 for the liquid
extruded from the tubes 7 under the thermal changes to which the instrument is
exposed.
So long as the changes of temperature are equal the equilibrium of the beam
remains, but when the bulb 8 becomes more highly heated than the bulb 9, it
extrudes a larger quantity of liquid from its tube into its reservoir than does the
latter, and the beam 2 consequently inclines in proportion to this amount, and a
record of its inclinations may be made by the means hereinbefore described.
The above described balanced wheel and corrugated box arrangements illustrated
in Figures 5 and 6, may also be used as differential-thermometers apart from the
coloring of the bulbs of their thermometers, and as true radiometers when colored
as described and unattached to the recording apparatus.
Having now described the nature and objects of the said Invention together
with the manner in which the same is to be or may be performed or carried
into practical effect, I would remark in conclusion that the improvements in

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Radiographs" which I claim as constituting the Invention communicated to me
by the said David Winstanley are:-
First. The application of the differential-thermometer, or of two liquid ther-
mometers, to a balanced beam or other equivalent device, in such a manner that
motion or pressure shall result upon the centre of gravity of the system being
disturbed, when the whole apparatus or one of the bulbs thereof is exposed to sun-
shine or other source of thermal radiance, and the combination with such an
arrangement of a lead-pencil or other marking instrument, in such a manner as to
utilize the said motion or pressure by causing it to press the point of the latter
.upon a record-sheet moved by clockwork at a convenient speed for the purpose
herein before stated.
. Second. The application of a clockwork movement to the balanced apparatus,
and its intervention between the latter and the marking-instrument, in such a way
that a greater pressure may be placed upon the pencil-point than that afforded
directly by the balanced apparatus alone.
Third. The similar applicatian of an electro-magnetic apparatus to the differential-
thermometer, and its intervention between the latter and the marking-instrument
for a similar purpose.
Fourth. The application of the differential-thermometer or of two liquid ther-
mometers to a delicately balanced wheel, which for the reasons given shall be
caused to rotate through varying lengths of arc under the influence of varying
degrees of solar or other radiation, and the application of such an arrangement to
any suitable one of those appliances now in use which give motion to a lead-pencil
in a direction at right angles to that of the record-sheet upon which it is to mark;
or the combination therewith of a marking-instrument and a slowly rotating
cylinder or equivalent device carrying a record-sheet, and by means of which the
movements of the wheel are registered, as and for the purposes hereinbefore
stated.
Fifth. The application of two air (or liquid) thermometers to connected metallic
boxes having opposite elastic and corrugated faces, and the combination therewith
of a marking-instrument and slowly rotated record-sheet, as and for the purposes
herein before stated.
And Sixth. The application of the differential thermometer or of two liquid ther-
mometers, substantially in the way hereinbefore described, to a moving sheet of
photographic paper, so as to obtain a record of the duration and intensity of sun-
shine by the variations effected in the terminal portions of the photographic
impression left by the light upon the paper used.
Each and all substantially as hereinbefore described, and as illustrated on the
accompanying Drawings.
In witness whereof, I, the said Clara Milton, have hereunto set my hand and
seal, this Twenty ninth day of January, in the year of our Lord One
thousand eight hundred and eighty.
C. MILTON. (L.S.)