IMPROVEMENTS IN THE MANUFACTURE OF SHEET GLASS
Year: 1857

page_text: LETTERS PATENT to William Clark, of 53, Chancery Lane, in the County
of Middlesex, Engineer, for the Invention of "IMPROVEMENTS IN THE
MANUFACTURE OF SHEET GLASS." —A communication.
Sealed the 28th July 1857, and dated the 19th February 1857.
PROVISIONAL SPECIFICATION left by the said William Clark at the
Office of the Commissioners of Patents, with his Petition, on the 19th'
February 1857.
1, WILLIAM CLARK, of 53, Chancery Lane, in the County of Middlesex,
Engineer, do hereby declare the nature of the said Invention for "IMPROVE
MENTS IN THE MANUFACTURE OF SHEET GLASS," to be as follows:
use, first, a furnace with a number of crucibles, which maintain a con-
tinuous supply of glass in a state of fusion.
Secondly, à reservoir or melting vessel receiving the fluid glass from the
crucibiles before mentioned, from which reservoir of glass the supply for the,
manufacture is furnished.
· Thirdly, guides or formers regulating the breadth sheet of glass; als":
refrigerators for cooling the edges of the sheet of glass.
Fourthly, an apparatus for lifting or drawing out the sheet of glass in the
manufacture:
And, fifthly, a cutting frame for cutting the glass of the required dimen-
sions.
In thefurnage or melting chainher larrange a series of crucibles or melting:

page_text: pots on either side with the furnace fire at either end. Towards one end of
the chamber the crucibles are gradually raised to a higher level, so that the
glass may flow from the one to the other by suitable ducts for that purpose,
and lastly, into the reservoir from which the sheet of glass is formed. This
reservoir is placed immediately over one of the furnace fires, and consists of
two parts. One, the principal, which receives the glass as before described;
and the other, a small floating vessel immersed in the fluid glass contained in
the other. This second smaller vessel is that from which the supply for the
manufacture is taken. This second vessel is supplied with fluid glass from the
main reservoir by an opening inthe bottom ;thethickness of the smaller vessel
serves however to somewhat isolate its contents from that of the larger vessel.
To produce the desired sheet of glass a piece of metal, which I call a bait,
whose length is equal to the breadth of the sheet of glass to be produced, is
heated red hot, and being suspended by a chain or cord over a pulley islowered
into the fluid glass. The glass becomes attached to the bait, which is then
drawn upwards, and as it rises extends the sheet. A continuous supply being
maintained in the reservoir below, the length of the sheet may be extended to
any required dimensions.
In order to regulate and form the glass of uniform breadth, two rods, having
curved or looked (rminations, are placed one on each side, the hooked parts
being immersed in the glass in the reservoir. These parts are capable of being
regulatedand adjusted bymeans ofscrews, both as regardstheir distance apart,
and the depth of their immersion in the fluid glass.
The refrigerators consist of vessels in which a circulation of water takes
place for the purpose of cooling the edges, and forming an edge or selvage to
the sheet of glass. These refrigerators are also capable of adjustment to suit
the breadth of the sheet of glass, and also to raise them more or less from the
glass in the reservoir.
In order to raise the sheet of glass and continue to extend it to any required
length a lifting apparatus is used, consisting of a series of horizontal shafts
disposed in pairs, one on each side of the sheet of glass; they have suitable
rotary motion imparted to them by bevil gear ;the two shafts acting in concert
are geared together or controlled so as to revolve in opposite directions.
Friction rollers are placed on each, which bear on opposite sides of the glass,
and by their contact and rotatory motion elevate the glass during its manu-
facture. These shafts and friction rollers are placed in pairs above each other
at suitable distances apart,and in number accordingto thelength of sheet to be
manufactured. The velocity with which the sheet glass is raised during the
manufacture regulates itsthickness ;the slower it is developed fromthe molten

page_text: mass in the reservoir .below the greater substance it will have; increase of
speed renders it thinner.
The lifting apparatus is moveable in all directions, and when the sheet
of glass is formed it is transferred to a vertical standard frame furnished
with sliding and swinging frames, on which the glass is placed while sus-
pended; it is then pinched tight, and cut across at any suitable distances
apart by means of a diamond.
SPECIFICATION in pursuance of the conditions of the Letters l'atent,
filed by the said William Clark in the Great Seal Patent Office on
the 19th August 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, 1, WILLIAM
CLARK, of 53, Chancery Lane, in the County of Middlesex, Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by her Letters
Patent, bearing date the Ninteenth day of February, in the year of our Lord
One thousand eight hundred and fifty-seven, in the twentieth year of Her
reign, did,' for Herself, Her heirs and successors, give and grant unto me,
the said William Clark, Her special licence that I, the said William Clark,
my executors, administrators, and assigns, or such others as I,the said William
Clark, my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN THE
MANUFACTURE OF SHEET GLASS," a communication, upon condition (amongst
others) that I, the said William Clark, my executors or administrators, by an
instrument in writing under my, or their, or one of their hands and seals,
should particularly describe and ascertain the nature of the said Invention,
and in what manner the same was to be performed, and cause the same
to be filed in the Great Seal Patent Office within six calendar months
next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that 1, the said William Clark, do hereby declare
the nature of my said Invention, and in what 'manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, reference being had to the two Sheets of Drawings hereunto
annexed, and to the letters and figures marked thereon, (that is to say):-

page_text: This invention relates to a means of manufacturing window glass in con-
tinuous sheets, the apparatus for which I have represented in the Drawings
hereunto annexed.
I will first enumerate the Figures, and then proceed to describe the
Invention with reference to the same. Similar letters of reference indicate
like parts in all the Figures of the same sheet. Sheet 1 contains
Figures 1, 2, 3, 4, 5, 6, 7, and 8; Sheet 2 contains Figures 9 and 10.
Figure 1, plan of the melting furnace and arch, in which the formation and
production of the sheet of glass is effected, which formation of the sheet I will
herein-after denominate spinning. In this Figure the dome of the furnace and
one of the tunnels or parts are removed in order to show the arrangement of
the crucibles, and the dimensions and arrangement of the fire bars. The
spinning arch is covered on the left side, and uncovered or in section at the
Fright in order to show a part of the spinning crucible. Figure 2 represents an
elevation of the melting furnace and arch, and the ironwork of furnace K
under the spinning arch. Figure 3 is a section through A, B, Figure 1. In
this Figure the crane or apparatus is shown for raising the sheet of glass in
progress of manufacture, which apparatus will herein-after specially describe.
Figure 4, section through C, D, Figure 1. The crane is here represented in
front elevation, (to render it more intelligible the crane is shown turned
round in Figure 3). Figure 5, section through E, F, Figure 1. Figure 6,
detail plan of a stage of the crane.
.
The new system of manufacture, which is the feature of this Invention,
consists in forming level surfaces or sheets of glass of variable dimensions
by spinning from a mass of glass in fusion, sheets of glass in a continuous
and regular manner, this mass of glass being constantly renewed by a
particular method of supply; all these results are obtained by means of the
arrangement herein detailed, forming an integral part of this Invention;
and which are,
First, the furnace, with crucibles arranged to maintain a continuous
supply of fused glass.
Secondly, the arch and flat spinning crucibles.
Thirdly, the guide supports and refrigerators of the sheet in course of
formation.
Fourthly, the crane or apparatus bearing away the sheet when formed,
and producing the spinning or manufacture of the sheet of glass.
Fifthly and lastly, the receiving and cutting frame.

page_text: FURNACE AND CONTINUOUS FUSION CRUCIBLES.
In this system the fusion of the glass is continuous, in order that the
spinning of the sheets may be continuous also.
To obtain this result, I employ crucibles having escape sluices_or. ducts,
Figure 7. The formation of these crucibles is very simple, consisting of a
channel G against the side of the crucible, and extending from top to bottom
on the inside, with the exception of about two and a half inches at the bottom,
which is left open so that the glass may pass into the passage G. The top
of this passage terminates in the sluice or lip a, by which the glass runs off.
Supposing this crucible filled with vitrescible substance, in proportion as
the fusion progresses, the crucible and passage G will be filled to an equal
height in consequence of their having a communication at the lower part.
If the introduction of materials is augmented continuously in proportion to
the progress of the fusion, when the crucible and passage Gare full and the
material continues to be introduced, the glass will reach the sluice a and
will run off.
=
It will be understood, that if the glass which thus runs off be received into
a second crucible similar to the first, this second crucible will eventually be
filled in its turn by the continuance of the introduction of vitrescible sub-
stances and of the fusion that takes place, and will also discharge the glass
up channel G, which will escape at the overflow at a, with which it is pro-
Avided. The number and dimensions of the crucibles can thus be increased
without changing the working of the apparatus.
The furnace represented in Figures 1 and 3 contains six crucibles b, c, d,
b, c, d, (eight or even ten, may be placed in similar arrangement and posi-
tion, if considered necessary for the supply required for the manufacture.
They are placed on a series of steps, so as to allow the duct a of each of
them to pass above the edge of the adjoining crucible, so that the feeding
and reception of the material in fusion from one to the other may take place
(see Figure 3).
The arrangement of the crucibles forms, as is seen in the Drawing, a series
on each side, or two series in the same furnace. The passage of the glass
proceeds in the direction of b to c and from c to d on one side, and b' to c¹
and from cod'on the other. At the extremities are two ducts or gutters e, e¹,
for transmitting the melted glass from the melting furnace into the receiving
trough H. Thus it will be seen, that by this system the matters being intro-
duced only into crucibles b, c, b', c', in proportion as the fusion takes place in
the whole series, the receiving trough will in time be filled. This arrange-

page_text: ment presents the advantage of taking the materials first melted from the
mass in fusion by withdrawing it from below the surface, which surface is
always less pure than the lower part: This mode of taking the material
constitutes one of the important points of my Invention, and without which
the spinning or the developing of the sheet ofglass would alwaysbe defective.
1, I', are two sets of fire bars, separated by the bridge J, which is for no
other purpose than todiminish the interior cavity of the furnace. The open-
ings, through which the vitreous materials can be introduced into the furnace
and the glass collected, are at f. The crucibles are placed and taken out at
the fire door K of the furnace.
ARCH AND FLAT SPINNING OR FORMING CRUCIBLE.
The spinning arch or furnace is adjoining the melting furnace, whence it
draws the necessary heat for maintaining the glass in a state suitable for
spinning the sheets. It consists of a narrow gallery or space L, in the
middle of which is the trough H for receiving the glass. The openings
g, h, h', i, i, conduct the heat thereto from the large furnace. The flames
after having passed through it. escape by the passage M, which leads to the
chimney N. A damper placed on this chimney serves to regulate the passage
of the flames and the heat in the spinning arch. At the right and left of the
5. furnace two small cells j, j, are disposed, which serve as reservoirs of heat;
and. also by means of them the gutters or channels e, e', can be placed in
position, or removed when required through the opening k, k¹.
The spinning crucible is formed in two parts, the receiving trough H, and
the spinning compartment or cell o. The trough is formed of a basin in which
the glass comingfrom the right and leftcrucibles enters, andis mixed together.
The cell o consists of a bottomless case or partition, formed of platina or
refractory clay, of the same composition as the crucibles. It serves to isolate
the point where the sheet of glass is spun or developed from the direct action
of the surrounding heat. The barrier it presents to the fire protects the sheet
at the moment of its formation, and allows it to acquire its origin, and by
cooling the consistence necessary for its further development.
.
The glass contained in the trough H passes into the cell o only at the
bottom, having no other entrance passage in the vertical sides of the cell o
during the spinning.
If. it is desired to give greater homogeneousness to the glass contained in
the cell o,that is, to mix more intimately the glass which arrives in the receiv-
ing trough from the right and left side, in order to prevent the breaking of the
sheets, which is often caused by the glass being in an insufficiently combined

page_text: state in the cell o; to effect this the cell o should be furnished with a bottom,
having a single and rather narrow opening, so that the glass coming from the
two points of supply must meet at this passage; by this means the mixing
will be more completely effected. The trough H is put in or withdrawn
from the furnace through the door P', and.the cell o is introduced into the
trough H from above..
PRINCIPLE OF FORMATION OR SPINNING OF SHEET GLASS.
In order to spin window glass flat, that is to say, in ribbons or sheets of
glass, the borders of the sheets must be colderthan the middle;in other, words,.
the hardness or resistance of the hot plastic glass forming the sheet must be
greater at the edges than in the breadth of surface, of which they form the
limits.
...:.
"
The success
this new system of sheet glass manufacture depends on the.
application ofsuitable micans ofpreventing abnormal formation or shrinkingof
the glass. For this purpose I have herein described two different methods:-
Firstly, the hooks of support which limit the breach of the sheet of glass;
secondly, refrigerators which cool by contact the edges of the sheet.
Hooks OF SUPPORT.
The hooks of support are represented at Figures 1, 3 and 4 of the annexed,
Drawings.
The supports, against which the edges of the sheet are brought, are simply
two hooks l, l, made of metal, or better, of refractory substances, which are
connected to a bearing having a socket m by iron rods n. The mechanical
arrangements of the socket are such as to allow of all the desired vertical and
horizontal positions being given to the hooks of support. First, the horizontal.
slides o are placed so that the hooks occupy the middle of the cell o in this.
position; a to and fro motion parallel to the central line of, the cell..is
given by screw p, see Figure 1, the ascending or descending vertical, motion
perpendicular to the first being given by the screw 9, see Figure 3..
COOLING BY CONTACT.
"
The refrigerators, which cool and form the edges of the sheet of contact,
are represented at Figure S.
These refrigerators are composed of a bent tube or channel r terminated at
one end. s. by a funnel, in which a little jet of water runs. This water fills the
ube, and after descending to the lowest point, re-ascends and escapes through
he spout t. The central part Q is supported on a pivot which supports the

page_text: whole apparatus. The parts thus arranged should bear very lightly on the
glass at the point R, so as to communicate, by gentle contact, the cooling
necessary for preventing the shrinking of the sheet, and ensuring it retaining
its proper form. The counterbalance serves to regulate the pressure
required tobe exercised onthe surface of the glass. In each spinning operation
there must be a refrigerator at each side of the sheet of glass, as at Figure S.
This apparatus acts like the hooking support for the edges of the sheet
which is being manufactured.
:
In order to vary the width of the sheet S, the refrigerators are advanced or
withdrawn towards or from the middle of the sheet.
The passage of water into the pipes is intended first to cool them, and con-
sequently to cool the glass they touch, so as to prevent the shrinking of the
sheet, and also to prevent the glass adhering to the tube, as the water prevents
the tubes becoming red hot by the contact with the glass.
THE CRANE.
The apparatus which will now describe is intended forlifting and removing
the continuous sheet of glass after its formation by the means above
described.
The crane consists of an apparatus having two, three, four, or more stages
of lifting action, according as it is required to exercise a greater or less
ascending force for spinning the glass.
The crane shown in the Drawings has four stages mounted on the same
frame. Figure 3 gives a sectional edge view of the four stages through line
A, B, Figure 1. Figure 4 represents a front elevation of the whole crane..
Figure 6 is a plan of the crane on an enlarged scale, showing the details
more distinctly. Figures 3 and 4 also represent the furnaces and the crane,
showing the exact position of the whole system of furnace and machinery,
except Figure 3, in which the crane is shown turned round for greater
distinctness.
T is a cast-iron frame on which the parts are fixed, U, pulley, receiving
and transmitting motion to the vertical shaft. V, which in its turn communi-
cales motion to the four stages of the crane by means of the bevel pinions
0,0,0,0. The bevel wheels v',',',', which receive the motion from pinions
v, v, v, v, transmit it in their turn to the horizontal shafts x, x, x, x, x³, x²,
,; the spur pinions y putting these eight shafts in communication with
each other a motion is imparted to them, similar to that of rolling mills.
Each of these eight shafts & and has two rollers z, made of pear-tree wood
or india rubber, placed opposite each other (Figures 3 and 6). These rollers

page_text: pinch between them the sheet of glass S which is being spun, they being
intended to elevate it by their rotary motion, and-friction of contact, and
pressure which they exercise on its surface. On each side of the rollers
moveable clutches X are applied for keeping the rollers fixed. These
clutches may slide the length of the shaft, and thus the rollers may be
disposed at any desired distance apart, according to the width of the sheet
to be manufactured. The clutches and rollers are fixed by thumb-screws,
which are inserted through the clutches and take on the horizontal shafts.,
The pressure of the rollers towards each other is exercised and regulated:
by means of weights Y suspended to bell-crank levers Z, Z, supported by the
arms 1, 1. The lever Z has its fulcrum at an angle, and has a joint on the
lower part of its vertical arm, by which it is put in communication withi
the rod. This connecting rod 2 has, at the opposite end, a boss, through the
centre of which the horizontal shaft passes.
Thus it will be seen that the pressure given by the weight Y is exercised.
between the rollers, in consequence of the opposite shaft on which the corre-.
sponding rollers are fixed being immoveable, that is to say, offering resistance
to the pressure.
In order to providefor any variation in the diameter and excentricity of the
rollers, occasioned by the wear of their circumference from contact with the
hot glass, I mount on the shaft x (Figure 6) a boss and rod 3, having a
moveable bearing, similar tothat of the compressing rollers above referred to.
The part 3 is terminated by a screw 4, having a nut 5 forming a stop against
the iron bracket 6. By means of these nuts, it is easy to change the position
of the shaft with which they are in communication forwards or backwards, so
as to keep the contact point always in the same position.
As the compressing rollers always press on the others, it is evident that they,
will participate in the motion communicated by nuts 5; the four bearings in
each stage slide on the planed ways 7.
The change of position of the roller shafts entails with it the necessity of
finding some means of preventing the disarrangement of the spurpinions y, y,
and bevil wheels . This is obviated by making use of the double gimbal
pieces S, which adapt themselves to every movement without inconvenience..
It is unnecessary further to describe this well-known piece of mechanism.
To obviate the horizontal displacement which might happen to the sheet
during the spinning, either from the unequal wear of the rollers, or from any
other cause, I mount all the horizontal shafts, as well as the ways 7 which
Support them, on a moveable cast-iron frame 9, Fig. 3, which may have a
vertical sliding motion imparted to it, which is effected by a screw 10 raising
f

page_text: or lowering the said frame, and consequently the eight horizontal shafts, which
are supported by it. The frame is held rigid in its place by two pins 11,
which fit into its foot. The opposite ends of the shafts are not displaced by
this movement.
THE RECEIVING AND CUTTING FRAME.
When the sheet has extended beyond the upper stage of the crane, it is
traversed aloft and passes into the frame represented at Figures 9 and 10,
Sheet. This frame is supported by a frame a of wood or cast iron,
balanced by a counterpoise 6 by means of cords or chains c which pass over
return pullies d.
b
The two vertical uprights of the structure which support the frame have
grooves, which receive the projections e, which form one body with the frame;
in this manner the frame can ascend and descend, but does not vary from the
vertical line. On the rigid framework of the frame is a moveable part m,
fixed by hinges f. This moveable part is double, that is to say, the sheet of
glass slides between two similar framings, separated from each other by a
space of from a fifth to a sixth part of an inch; this space can be widened or
reduced by means of screws g mounted on bevil gearing h, the whole being
put in motion by crank handle i.
The points of contact between the sheet and the double frame are covered
with small stuffed cushions, or of bands of india-rubber.
For the purpose of cutting the sheet held in this frame, a diamond is slid
along the horizontal rule j to the point corresponding with the hinges f, which
operation is described herein-after.
WORKING OF THE GLASS, OR FORMING IT INTO CONTINUOUS FLAT SHEETS BY
MEANS OF THE APPARATUS ABOVE DESCRIBED.
Supposing the furnace to be in full operation, the casting or fusion com-
mences; for this purpose the crucibles b, c, d, b', c', d'. Sheet 1., Figures 1
and 3, are filled with vitrifiable matters. In proportion as the lowering of
the level takes place owing to the fusion, each crucible is recharged three or
four times, so that they may be quite full after complete fusion. The pre-
paratory fusion being terminated.the continuousfusion then commences. For
this purpose new matters are introduced occasionally into the four crucibles
b, c, b', 6'. The excess of glass which these matters produce flows through
the channels G and a, and passes into the two crucibles d, d, which do not
receive the new additions of vitrifiable matters; from these it passes into the
gutters, e', and lastly into the receiving trough I, where the glass combines,
and
passes into the cell o before described by being admitted by the opening

page_text: at the lower part. The operation is continued in proportion as the fusion of
the last matters introduced takes place, until the trough and the cell o are
filled, as well as all the other crucibles. The spinning then commences; the
plate A, Figure 2, Sheet I., made of refractory clay, is lifted by the hooks
B, B', with which it is furnished (during the preparatory fusion this plate
covers the opening of the spinning furnace); the cell is then seen as repre-
sented at Figures 1, 3, and 4, Sheet I. At this moment the socket bearings
are placed in position, and the hook supports lowered below the surface of
the bath or vessel of glass, so that they may get red hot and adhere to the
glass; care should previously be taken to fix the bearings in such position
that the hooked supports are at the centre of the cell.
:
The bait C' of iron previously made red hot throughout its lower edge, so
that it may adhere to the glass, is lowered vertically into the vitreous mass
power from any suitable source D' is brought to bear on the bait C', which is
gently removed with the glass adhering to it. It is necessary that the
supports 1, 1, should accompany it in its progress, and touch it at the two
extremities for about an inch and a half above the level of the glass bath,'
which movement is easily effected by means of vertical screws q, q'. The
hooks or supports then stop, and the bait C continues its ascending motion,
drawing with it the sheet of glass in course of formation, the two edges of
which keep close to the supports l, l.
1 have here indicated the means of preventing the glass shrinking in its
width, by attaching to it the hook supports; but the manner of operating by
cold contact if preferred will easily be understood by reference to the
preceding description.
At this stage of the operation the tendency to shrinking tends to make
itself manifest, but as the glass has already cooled during its ascent through
the inch and a half space, which separates the level of the mass of the bath
from the top of the hooks, it ensures that the edges of the sheet form only
at their origin the portion of a circle at E, E', Figure 4, Sheet 1., at which
point the cooling increases upwards on all the zones parallel to the horizon.
The more the glass is raised the tendency to shrink diminishes gradually,
and disappears altogether a little higher up, which produces the uniform
consistency of the sheet of glass throughout the whole of its extent upwards.
The bait C soon reaches the crane, care being taken to open this part of
the apparatus before proceeding to spin or form the sheet of glass; when the
bait C passes the first stage of the crane, the pressure of the wood or india.
rubber rollers, caused by the action of the lower weight Y, is allowed to act
on the sheet so as to carry it upwards.

page_text: The operation just described is repeated after the passage of the bait C',
above each stage of the rollers. Lastly, when all the rollers, intended to
assist in the operation of spinning by raising the sheet of glass are caused to
exercise a pressure on the surface of the sheet of glass, the vertical shaft V
alone produces the rising action, and continues the spinning operation; the
bait C then becomes useless, and is removed from the endless sheet of glass
by sliding a cutting diamond along a rule placed horizontally for the purpose.
Before commencingthe operations just described, the. receiving and cutting
frame and its framework should be drawn back, as seen at. Figure 10, Sheet
11., so as to allow of bait C being raised; this latter being detached, the
frame is brought back to its original position by means of lever n, which acts
on the lower part of the framework. The sheet is then held between the
cushions of the double swing frames. When it has reached the required
height for making the sheet, the screws 9 are tightened by the crank i; the
double frames approach each other, & grip the sheet which they embrace;
a diamond is then at once slid across the length of the horizontal rule j, at
the point coinciding with the hinges; the stop o is then opened, the handle p
ia seized, and the frame also drawn together in order to determine the
breaking of the glass at the point traced by the diamond.
The hinges permit the lowering of the moveable part of the frame to the
horizontal position; in this position the sheet is taken out by opening the
double swing part of the frame; the whole is then closed, the screws loosened,
and the operation repeated to be thus continued indefiniely, taking care
that the crucibles are fed with vitrifiable matters in proportion' as they are
consumed in the manufacture.
In order that the spinning orformation of the sheet of glass may be effected,
the angles F; F1, Figure 3, Sheet I., of the wall of the arch must be below
the horizontal level of the edges of the cell o, or the heat of the interior of the
furnace will act on the sheet in formation, in which case it will not be pos-
sible to acquire the necessary consistency by cooling for removing the glass,
to which it is attached at its base; a stretching out, and consequently, a
depreciation in thickness would be produced, and the spinning of the sheet
become imperfect.
By experience I find that for spinning thick glass, the ascending motion of
the sheet of glass must be relatively less rapid than for spinning thin glass;
so that if at a given speed glass is formed or spun thin, it will be spun
thicker and thicker in proportion as the rate of ascending motion is reduced.
This manufacture of glass only requires two workmen, a spinner and a
cutter; the spinner superintends the attaching of the hook supports, and the

page_text: raising or lowering them according to the exigencies of the work; he also
regulates the width of the sheet, the cutter being required to detach the
sheet from the principal sheet or column of glass, and to deliver it to the
warehouseman.
Having described the nature of the Invention and the manner in which
the same is performed, I declare that what I claim as the Invention of im-
provements in the manufacture of sheet glass, intended to be secured by the
herein-before in part recited Letters Patent, is,-
First, the maintaining a continuous supply of glass in fusion, for the opera-
tion of spinning or forming sheet glass, by means of crucibles furnished with
ducts or passages, so formed and arranged as to allow the glass to flow away,
from the bottom, and thus always ensuring the escape of the purest glass
first.
1
Secondly, I claim spinning or forming sheet glass by the aid of supporting
hooks or by refrigerators from a cell-or chamber, having no communication
with the supply of glass from the furnace at the upper end, and surrounded
with glass in a state of fusion from which it draws the necessary supply from
below as described.
Thirdly, I claim the use of the frame or apparatus described for removing
the vertical sheet of glass, & for cutting and delivering the same.
In witness whereof, I, William Clark, have hereunto set my hand
and seal, this Nineteenth day of August, in the year of our Lord One
thousand eight hundred and fifty-seven.
25 Witness,
W. G. E. SWINNOCK.
WILLIAM CLARK. (L.S.)