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smoke are prevented from falling into it; as more than half of the glass is ground away also any fragments off the arch and “ tears" before it is in a fit state for sale ; and as the are effectually excluded. Farther, the de duty is paid upon it in the state in which it struction of the furnace cannot be so great is brought out of the annealing oven the loss as on the old principle, where the arch has is very great. first to receive the heat. But should it be
We shall proceed now to describe the preferred to leave the cistern uncovered there
accompanying engravings, and in the is no possibility of the angles of the bricks falling into it, as the patentee covers the fur
course of doing so shall have occasion to nace in the manner shown in the engray
point out several subordinate improveing, fig. 1, and afterwards more parti.
ments of a very useful character. cularly described, with a cone of fire clay
Fig. 1 is a vertical section of a platein one piece larger in diameter than the cis. glass furnace constructed according to tern. The system of heating from below has
Mr. Bessemer's plan, and fig. 2 a hori. also the advantage of considerable saving of zontal section or plan taken on the line fuel and time, as heat is much more easily A B, through the upper openings where transmitted through platinum than through the melting cisterns are introduced. fire clay.
A A is the masonry of which the fur. Another valuable improvement of Mr.
nace is composed, being built of fire-stone Bessemer's consists in placing each cis
of the usual description. B is the main tern
flue or chimney, CCCCCC six open
ings or compartments, each forming distinct in a separate chamber, whereby each cistern furnaces with fire-places, D, to each, and may be removed for casting when ready, ash-pits, E, under the same. The interior without lowering the temperature of the rest. of the furnaces C are lined with fire-brick, In the present furnaces five minutes are and at top of each is a conical cover F, comallowed for each of the six cisterns (that posed of the same materials. These coverbeing the usual number employed) being ings have holes at top communicating with cast, and if longer time were taken the last the small flues G, which lead to the main would get cold, and if it were left till the chimney B. The flues G are each provided heat was got up again, the glass would be with dampers. The peculiar form of the spoiled by the undue evaporation of the top F, of the furnaces C, is of more imsalt.
portance than may at first sight appear. The next improvement we have to notice
In the process of manufacturing plate glass, relates to the annealing oven, and con
as at present practised, a considerable eva. sists in
poration, as before noticed, takes place
during the process of melting, and from the forming at the bottom of the oven a flat usual construction of the furnace and posisurface sufficiently large for annealing one tion of the melting pots placed therein, a plate. The oven may contain many such condensation takes place on the dome of the surfaces. Each surface is composed of a furnace, which causes what are technically number of blocks or hollow tubes, of fire called “tears' to drop into the melted glass, brick or other suitable material, first sub which produce the most injurious effects. It jected to a heat at least four times greater is to obviate this serious defect that Mr. than they will afterwards have to undergo. Bessemer gives to the cover F its conical When cold they are fastened or connected form (glazing it also on the inside) so that together by bolts and nuts, or other means any fluid which may form upon it runs down (their sides being ground to fit close,) hollow to the base of the cone and drops outside the cubes being preferred for this purpose, as melting pot. H H is a circular piece of fireaffording facilities for meeting together and clay, which is moulded to fit the ledge (I) begiving the required strength with a small tween the furnace C and fire-place D, and weight of materials. These annealing tables upon which it rests, forming a stand upon or surfaces are ground to a perfect level by which the melting pots are placed whilst in the grinding apparatus now used for grind. the furnace (see figure 3, where these stands ing plate glass. Upon these tables or sur are shown on an enlarged scale); there are faces the plates of plastic glass undergo the openings h which allow the flame and heat annealing process and are allowed to cool, so from the fire-place to pass through and cir. lidifying in contact with the level surface and culate round the melting pot. J J are doors thereby becoming equally level. By this composed of fire-brick and strongly clamped means a great saving is effected, as owing to together with iron bands which close the the very uneven surface of the present oven furnaces during the process of melting. K the plate of glass is often so very much out is the refining cistern melting-pot, made of of the level, and the surface so indented, that the usual material and of the usual form, with
the exception that the bottom L is com resorted to as a means of removing the vari. posed, as before explained, of platinum, and ous impurities on the surface of the metal, made moveable to allow of its being removed, for which purpose a number of men surround as occasion may require, to other cisterns. the cistern with a long handled skimmer and This cistern is shown on an enlarged scale in take up the glass in small portions and turn figure 4.
it over the edge of the cistern. The evils of When the cistern is removed from the this system are, that they cannot see how furnace, previous to turning out the metal, much or how little they have done from the an operation called “ skimming" is usually intense light and heat affecting the eyes, and
that many air bubbles are inevitably intro metal plate Q between the rings and the pot, duced into the mass by the falling back of as shown in figure 5, the ring and the scum the metal that hangs to the skimmer. within it will remain on the top of the plate, To effect the skimming without ad
and may be readily removed from the pot. mitting air bubbles into the mass of the
All this is more clearly represented in figure
6, where the ring is shown on an enlarged melted glass, Mr. Bessemer places
scale. barred rings PP on the top of the pots, keeping the level of the glass about the junc The arrangements for exhausting such tion of the ring with the pot, and by passing a air bubbles as may not have escaped
during the refining process are shown in arrangement of having chambers ready exthe elevation and plan, fig. 7 & 8:
hausted, an almost perfect vacuum is formed
in much less space of time than if the opeAs soon as the melted glass is removed ration had to be performed by the air pump from one of the furnaces C, the cistern is in direct communication with the cylinder, placed within a metal cylinder S, which is after the cistern had been placed in the cylined with fire-brick to prevent the escape linder. The atmospheric pressure being thus of heat as much as possible, the bottom of removed from the surface of the melted glass the lining being ribbed or grooved so as to the globules of air contained therein will form a communication with the opening T become greatly expanded, and thereby acin the centre. The top edge of the cylinder quire sufficient floating power to rise to the S is accurately ground and fitted to the bot. surface, and this operation requiring only tom of the cylindrical cover U, which is sus about two minutes, the glass suffers scarcely pended over it, and as soon as the melting cis any loss of heat, and is now in a perfect tern is placed on the cylinder S, the cover U state for casting, is lowered on to it. Y is an air-pump, which is kept in action by a steam-engine, and com
The construction of the improved anmunicates with three cylindrical vessels W2
nealing oven is shown separately in figs. W2 W3 by the pipe V, which form vacuum
9, 10, 11, and 12, each of which how. chambers. To these chambers pipes Z1 Z2 Z3 ever, represents but one seventh part of are attached, which are connected to the valve
the area of the oven. It consists of a box a, and which in fig. 7 are shown closed number of square blocks,by the slide b; this slide is provided with a which are hollow and open at bottom (as spring and has an opening, C, in the centre
particularly shown in figures 11 and 12.) to form when moved over the openings of They may be made of any size to suit the the pipes 2 (by turning the handle e), a form of the oven, as may be most convecommunication between the valve box and
nient, but the patentee prefers that they the vacuum chambers; but when placed in should be about two feet square. The sides the position, as shown in fig. 7, a communica
are ground and fitted to each other, and tion is formed between the valve box and
they are connected together by screws and the atmosphere, which will allow the air to
nuts, grooves being formed in the sides of flow into the cylinder S, by means of the each block, into which clay or cement is pipe d, and the cover U to be lifted up; forced to prevent shifting, as shown at t in is a handle, the spindle of which is screwed figs. 10 and 12. As soon as the whole is fitted and works in a box f, and by this means the together it forms a surface on its upper side, valve is moved backwards and forwards.
as shown in fig. 9; and previous to its being The object of this apparatus being to extract placed in the oven it is subjected to the ordiany air or air bubbles that may be left in the nary grinding machine and made as level as melted glass after it has been removed from
possible, after which it is set in sand in the the refining furnace, previous to its forma
ordinary way. In some cases it may be detion into a plate, it will be evident that if a sirable to have moveable bottoms to the vacuum is maintained in the chambers or
annealing ovens, and for that purpose the vessels WIW2 W3, that the air contained in
patentee provides rollers k k, as shown in the cylinder S and cover U must rush into figures 13, 14 and 15, upon which it can the vessel W1 by the pipe Z1, whereby its be moved in or out as occasion may require. density
will be lessened in proportion as the Fessel Wi is larger than the vacant space in
The claim of the patentee as regards the cylinder S and cover U. The further the improvements we have described is rotation of the handle e will bring the slide
as follows:b over the second pipe Z, closing the com First, to the forming of furnaces in such munication between the cylinder S and ves manner of solid masonry in the centre and sel Wi, and establishing a communication with separate chambers and fire-places arwith the vessel W2, and cylinder S, the small ranged round that solid centre, as that each remaining portion of air left in the cylinder cistern or pot may be heated independently S again divides itself equally into the in of its neighbouring cistern or pot, and withcreased space thus formed. The still further drawn from the furnace to be emptied of its progress of the handle e brings the slide 6 contents,when the glass contained therein is over the opening of the last pipe Z3, and in a fit state for being operated upon without closes the communication with the chamber affecting the temperature of the other pots W?, whereby the minute portion of air left or cisterns in the furnace, as shown in figs. in the cylinder S and cover U again expands 1, 2, 3; as also the conical-shaped covers itself into the increased space thus formed placed over each separate furnace, and glazed between it and the chamber W3. By this inside to prevent the falling of tears into the
PROGRESS OF FOREIGN SCIENCE.
Second, the introduction of a Royal Academy of Brussels, to found a platinum bottom to the cistern or pot, and prize for the best essay on this subject. the application of a top ring thereto, as shown Government further provided the requiin fig. 4; and the perforated ring on which site funds for the publication, in a cheap the cistern or pot rests, as shown in fig. 3. form, of such of these essays upon the Third, the mode of skimming by means of
modes of working coal mines subject to the top ring and handled cutting plate, shown in fig. 6. Fourth, placing the cistern or pot
foul air, as should be deemed by the comin a vacuum, in order to exhaust the air from
mission of the academy worthy of selecthe glass contained therein, previous to its
tion for the
purpose. being poured upon the table, as shown in
The result was, that fourteen essays figs. 7 and 8. Fifth, the annealing table
were received ; some of these were by (the various parts of which the patentee pre
whose ardor scribendi outran fers to be of fire-brick, but which may be
their knowledge of their subjects; but made of stone of any suitable kind to stand others were considered, and justly, as of great heat) united together so as to form one
In May, 1840, the Acasolid mass, and ground or otherwise brought demy heard the report of M. Cauchy, to a perfectly level surface, as shown in one of the Commission appointed to exafigures 9, 10, 11 and 12, 13, 14 and 15.
mine the essays, and determined that in consequence of the publication between the time of the prize being offered and the receipt of the essays, of an elaborate
paper, by M. Courbes, in the Annales Belgian Publications on Prevention of des Mines, on the same subject, the prize Accidents in Mines-- Ventilation
of two thousand francs should not be The Safety Lamp, &c.
awarded ; but that three gold medals, of The Government of Belgium has, within eight hundred francs value each, should the last few years, set a noble example be given to the authors of the three best in endeavouring to elicit all the informa essays, and two medals in silver to the tion that science and experience can next in merit, that these five essays produce, with respect to the deeply im should be published at the expense of the portant questions to that country and to state, and fifty copies given to each of our own, which relate to the best and the authors, along with the report of the most effective and practical methods of Commission upon safety latops, instituted diminishing the dangers which beset the at Liege. The essays were all sent in miner, in coal-pits which are subject to under epigraph signatures—the names fire-damp. Much as has been effected of the authors not being known until in our own coal-fields, by the science of after the decision. The five memoirs, such men
as Davy, Clanny, and Ste together with the report upon improved phenson, and by the practical skill and safety lamps, are now published, and judgment of engineers of the class of constitute a single 8vo. volume, containBuddle, lamentable accidents are even ing a mass of systematized information yet of frequent occurrence ; but the spe that, if translated into English, could not cial conformation of our great coal-fields fail to be of the highest value to those of gives facility for ventilation (the great our countrymen who are engaged in coal antidote to fire-damp accidents), which workings, and of whom it must be adthe different structure of the Belgian, mitted, that however great and unequaland most of the other continental coal led may be their practical skill, energy, measures, does not present.
and courage, guided by a judgment the With a most laudable anxiety to meet most prescient, still, as a class, the these difficulties—to place before the amount of correct and exact scientific public, for the common benefit of all knowledge, upon the matters of their whatever had been done in Belgium or own avocations, possessed by them, is other countries, in improving the work comparatively small. ing of mines troubled with foul air, a To attempt an analysis of this closely Royal ordonnance, of the 22d of June, printed volume, so abounding in details, 1839, founded on a Report of the Mi would be impossible ; the best idea that nister of Public Works, M. Nothomb, we can give of the sort of matter it condecreed that a sum of two thousand francs tains will be by a specimen, and we should be placed at the disposal of the choose one, passim, and will take part of