MEMOIR ON THE MANUFACTURE OF GLASS IN BOHEMIA. thing of the sort which has before been manufactured. Of this, too, we are certain, that there is ample room for the operations of both companies, or indeed for any ten such companies; and that it is a great mistake, therefore, in the promoters of the Warlich Company to suppose that they have anything to gain by affecting an ignorance (which is ridiculous) of the existence of their powerful rivals, or seeking to depreciate the value of their commodity (which is incontestable). MEMOIR ON THE MANUFACTURE OF GLASS IN BOHEMIA. BY M. L. P. DEBETTE. (Continued from page 304.) The regulation of the fire requires two firemen for each furnace, who relieve each other in turn, so that there is always one at the furnace. They receive each 1.30 dollars per week, or about 20 cents per day. Each glass-pot is tended by one blower, aided by his apprentice, who brings the moulds, removes the finished pieces, &c. The pay of the blowers, as well as that of the cutters, is 9 cents per shock of glass worked. The number of pieces which form a shock, varies according to to their nature, and the rate is so arranged, that a good workman may easily gain 1 dollar in 12 or 15 hours' work. Besides this, in the establishments in which the above tariff is established, they are in the habit of giving to the workmen, so long as they are engaged in the works, a wooden cottage to live in, and a kitchen garden of sufficient size for their use, and to permit them to keep a cow, without being subject for these to any extra labour or manorial dues; so that it is extremely difficult to fix, in a precise manner, the real pay of the workmen, and of course the cost of the glass. Of the expense for fuel.-I shall give here the annual consumption of fuel in each establishment, supposing it to consist, as is 319 usually the case, of two melting furnaces, the working and repair of which succeed each other, so that there is always one in action. In the glass works of the Count of Buquoi, where they use dry wood not roasted, they consume annually 1255 cords of wood (160706 cubic feet) when they are making table glass, or fine glass, as at Silberberg, and 1507 cords (192847 cubic feet) in making window glass, as at Schwarzthal, the increase arising from the fact that the glass pots there are rather larger, and the time of working being smaller, a greater number of meltings are made per week. In the establishments of MM. Meyer, at Winterberg and Leonorenhain, where the wood is slightly roasted before employing it to heat the glass furnaces, they consume annually 1130 cords (144812 cubic feet) in making table glass and fine glass, which gives an economy of one-tenth over the consumption at Silberberg. This great economy of fuel is evidently due to the fact, that a certain quantity of heat is necessary to drive out the hygrometric moisture of the wood, and to vapourize it entirely, and that in Silberberg this heat is taken from that developed in the melting furnace, while in the works of MM. Meyer, as in those which we shall hereafter mention, it is taken from the flames which escape from that furnace. At Goldbrünn, Stachau, and Vogelfanghütte, there is consumed 40 2 cubic feet per day, or 1143 cords per year (146578 cubic feet), a result which accords in a remarkable manner with that obtained from the works of Winterberg and Leonorenhain. CHAPTER IV.-Manufacture of Table Glass and Fine Glass. As soon as the glass of the preceding casting has been worked up, each crucible is charged with about 154 lbs. of materials previously fritted, taking care to put the arsenic first, at the bottom of the crucible. This mixture varies, in a very notable degree, in different establishments, as may be seen from the following table : 60 Carbonate of potassa Caustic lime.... Carbonate of lime.... Arsenious acid...... Peroxide of manganese Old glass broken and sifted.. 350 THE MANUFACTURE OF GLASS IN BOHEMIA. (1) White table glass, first quality, from Schwarzthal, a little white arsenic, and a very little peroxide of manganese are added. (2) White table glass, from Neuwelt, (M. Perdonnet,) a small quantity of nitre, oxide of manganese, and white arsenic are added. (3) Very white table glass (M. Penhok.) (4) Common table glass (M. Hermbstädt.) (6) (7) (8) (9) Fine glass, called Bohemian crystal, from various establishments. To (6) (7) and (9) a little white arsenic is added. As soon as the glass pots are charged, the fire is increased by putting a very little more wood frequently upon the grate; gradually the mixture contained in the glass pots melts, and soon very small bubbles of gas begin to be disengaged from the midst of the fluid mass; the temperature of the furnace is continuously raised, and from time to time the melted mass is stirred with a piece of wood, in order to facilitate the disengagement of the bubbles, which gradually augment in size. The workman judges that the fusion is nearly completed, when the bubbles are formed but rarely, and of large size. He then ceases to stir the fluid mass, and suffers it to rest for a full hour, the fire being suffered to fall slightly, so that the glass may take sufficient consistency to be worked. The melting is then finished, and the working, properly so called, commences. Each melting pot is then served by a blower (blaser) and an apprentice (lehrjunge), as we have already said. The iron tubes which they use are nearly 5 feet (1.5 metre) long, weigh from 8 to 11 pounds, and are provided with a handle of wood about 13 inches (33 centim :) long, to assist in the manipulation. As the working of glass is a thing very difficult to explain, and one which must actually be seen in order to be well understood, I suppose that I may dispense with details upon this subject, feeling certain that in the remarks which I have to make I shall be understood by those who have studied the art of manufacturing glass. The forms, or moulds, employed are generally made of two pieces, except in very particular cases where extremely simple articles are to be made, such as ordinary drinking glasses, to which a handle is often afterwards added, as in beer glasses, while the glass is still sufficiently soft to weld. These forms are of wood, clay, brass, or copper; those of cast-iron being not yet employed in Bohemia. Those most used are of wood, which the apprentice takes care to moisten very frequently, so as to prolong their duration by preventing them from taking fire. In these arrangements it will be seen that there is no division of labour, and the same workman begins and finishes the pieces, so that the work is executed rather less rapidly than in France. In fine, the melting of the glass lasts from 18 to 20 hours, the working properly so called, from 14 to 15, making in all 32 to 35 hours for the whole operation. The loss by volatilization is from 15 to 20 per cent., and consists of water, carbonic acid, and alkali; there is obtained from 88 to 110 pounds per pot of finished glass, not including the loss, during the manipulation. The annealing of the glass is performed by placing them, while still hot, in clay crucibles, ths of an inch in thickness, placed in the annealing furnace annexed to the melting furnace. The interior dimensions of these crucibles are as follows: Diameter at the mouth.... 15.68 inches. 66 bottom 66 .... ... 15.68 19.6 ..... Depth When one of these crucibles is entirely filled, it is withdrawn by one of the doors of the furnaces, constructed for this purpose, and suffered to cool slowly in a corner of the establishment; the cooling being retarded as much as possible by covering it with a sheetiron lid. It may be easily seen how imperfect this process is, when compared with the constant annealing furnaces now in use in France, the use of which has not yet extended to Bohemia. CHAPTER V. Of the Manufacture of The bottle glass of Bohemia is very slightly coloured, and would sell very badly in that country, if it had the deep green, or yellowish green colour which our glasses present. In most of the glass establishments they make it by re-melting old glass with that which runs out upon the hearth of the furnace when a pot breaks by age, or accident. In some other glass works, such as that of Gross-Luckawitz, near Chrudim, the bottle glass is made from a very friable quartzose sandstone, belonging to the quader sandstein formation of Bohemia, and sufficiently white for this purpose, from a very calcareous clay, a kind of tertiary marl, very recent, and very often covered with a formation of turf, and from glauber-salts, (sulphate of soda,) the residue from the preparation of nitric acid in the manufactory of chemicals established at the same spot, and belonging to the same proprietor, the Prince Auersperg. There is added besides these a certain quantity of charcoal dust to reduce the sulphate of soda. This establishment possesses but one circular glass furnace, containing six pots, the charge of each of which is about 177 pounds. The working THE EARL OF DUNDONALD AND THE season of this furnace is six months ; the respite necessary for the repairs two months, and the blowers are not paid by the piece, as is the usual custom, but receive each one 1032 francs (206 dols. 5 cents.) for the working season. They are besides exempt from all rent, or manorial dues, for the small portion of land which is allotted for their use. The melting of the glass takes place exactly as I have described it in the preceding chapter. Then the blower takes upon the end of his tube a quantity of glass sufficient to form a bottle, by dipping it two or three times in the glass pot, and blows through the tube, which he turns, guiding it by a bar of iron, while the apprentice presses upon the glass a block of wood, which he dips in water from time to time, when he sees it take fire. Near the blower there is placed a tub full of water, from which he takes it from time to time in the hollow of his hand to cool his tube, when he finds it heat too much. When the piece becomes too cold, he reheats it, introducing it into the furnace by the opening which is above the glass pot, then resting his tube upon an iron hook which projects from the embrasure, he gives it a continuous motion of rotation, in order to prevent the glass from bending or inclining to either side. As soon as it has acquired nearly the desired form and size, he finishes it by placing it in a wooden mould, formed of two pieces, which is held by the apprentice, turning it, and blowing into it continually. Sometimes, however, a mould of a single piece is used, as is practised almost always in France, but here far more rarely. The bottles have ordinarily their bottoms entirely flat. As soon as the bottle has taken the desired form, the workman withdraws it from the mould, and his apprentice takes it by the bottom by means of a rod having a drop of melted glass upon it. The workman then detaches it from his tube, and forms the head by applying a cold body, or, in case of necessity, even by letting fall a drop of cold water upon the place which he wishes to cut. It is then slightly reheated by his apprentice, and a glass band wound around the neck to strengthen it. The bottle is then finished, and nothing remains but to transport it to the annealing furnace, which is sometimes joined to the melting furnace, sometimes separated, as at Gross-Luckawitz. In the latter case the furnace is kept at a dull red heat for four or five hours after it is full, then all the openings are closed, and it is left to cool spontaneously. To clean his tube, the workman dips it, while yet hot, into cold water, the glass at the end crumbles, and is detached by a single blow of a ham mer. To conclude, in the manufacture of bottle glass the melting lasts from 18 to 20 hours, the working 8 to 10 hours, in all from 26 to 30 hours. (To be continued.) THE EARL OF DUNDONALD AND THE "JANUS" STEAM SLOOP. We quote the following articles of "Naval Intelligence" from the Times : "Chatham, May 2.-The Janus steam sloop is still in the hands of the engineers, and is likely to be so for some time; for the last three days several efforts have been made with the engines to make them work without success. On Thursday, the Ruby steam sloop took her in tow, and pulled her against a strong tide, which had the effect on her rotary engine of making the wheels turn round two or three times." a.m., "Chatham, May 17.-The Janus steam sloop.-Yesterday morning, at 4 o'clock, another experiment was made by the engineers with the rotary engine, in the presence of Captain W. H. Shirreff, the superintendent of the dock-yard; and after many hours' trial, without making any revolutions, it was given up. This vessel has already cost 33,0007., out of which sum 9,000l. is for the engine. Since the above estimation of the expenses of this untoward vessel has been given in, there has been a considerable outlay incurred in alteration, fuel, &c., amounting, it is supposed, to upwards of 1,000%." So much for amateur engineering and Government favouritism! When the Lords of the Admiralty thought fit to make a trial of rotary engines, the fair and judicious course would have been to appoint a scientific commission to enquire into the subject, and report which of all the numerous engines of this class are most deserving of being tested at the public expense; but, instead of that, without making any enquiry at all, or at least without making enquiry of any persons more qualified to give an opinion on the subject, than that respectable peerof-all-work, Lord Brougham (who is generally understood to have been the prime instigator and adviser of their lordships on the present occasion), they select that of the Earl of Dundonald, as being alone worthy of their high countenance. The result of this sensible and faithful mode of administering the resources of this country is now before us. A sum of 10,000l. has been thrown away to no purpose,-thrown away on a scheme for which nothing else than failure was ever anticipated by the most competent judges; a sum, too, which, properly applied, might have defrayed the cost of testing every invention of the sort which was worth testing. So much, too, for legislating for individual cases, and for the sake of private interests! The rotary engine which has thus failed so signally is the same which gave rise to the late Act empowering the Privy Council to prolong letters patent for a second term of 14 years, and the patent for which was the first actually prolonged under that Actthe same which Lord Brougham was SO apprehensive would be pirated by all and sundry, before his noble friend, the Earl of Dundonald, could reap those advantages from it, to which its exceeding ingenuity so eminently entitled him, but which there were others (ourselves among the number) who thought to be as little in danger of such a fate as any invention ever patented-the same which, in the judgment of his eccentric lordship, (after "much thinking on the matter,") could be only suitably rewarded, by granting to the noble inventor, a monopoly of it for double the term, for which any such monopoly was ever granted since the days of Watt!! had her steam up for four hours before, and started off at full speed; the Vesuvius only 14 hour, and made for a while but thirteen revolutions per minute instead of sixteen, her more usual number. In the course of between five and six hours steaming, through an extremely smooth sea, the screw-propelled vessel gained on her paddle-wheel competitor about two miles. The Vesuvius then bore out to sea, expecting that as the Rattler was sent in company, for the express purpose of testing her deep sea-going qualities, she would take the same course; but for some reason, which remains to be explained, the Rattler kept in shore-gave the other vessel literally the slip-and so gained full 30 miles of distance in the run to the Firth of Forth. When next fallen in with, she was coming out of the Firth; she returned back with the Vesuvius, and for about an hour there was a neck and neck race between them; but, at length, the Rattler shot a-head, and went fairly round her antagonist. And so this further trial ended-perhaps, the most unsatisfactory of all the trials which have been yet made. The Vesuvius, we find, is a vessel of 280 (nominal) horses power, and, therefore, superior in this respect to the Rattler; but she has been always a slow-goer-drawing 13 ft. 9 in. forward, and 13.1 aft, and but seldom attaining a mean speed of more than 7 or 8 knots an hour. THE FALL OF THE YARMOUTH SUSPEN BRIDGE. The Coroner's jury have returned the following verdict on this case: "That the deceased came by her death by the falling of the suspension bridge across the River Bure in this borough, on the 2nd of May, 1845. That the falling of the bridge was attributable immediately to the defect in the joint or welding of the bar which first gave way, and to the quality of part of the iron and workmanship being inferior to the requirements of the original contract, which provided that such should be of the first quality. Although the jury do not wish to add more to their verdict, they wish to express the fullest concurrence in what had fallen from the coroner as to the facilities which had been afforded by the Messrs. Cory in the prosecution of this enquiry, which had been so scientifically conducted by Mr. Walker, who had been deputed by Sir J. Graham to come down and examine into the cause of the accident. They are of opinion that every possible precaution has been taken by the original proprietor of the bridge, and that had the clerk of the works performed his duty in the proper examination of the work, the calamity which they now deplore would have been prevented. They beg also to express their sympathy with the present proprietors of the bridge, whose entire conduct has reflected the greatest credit upon them, in the kindness they had shown to the survivors of those who had been lost by the sad event." We shall give the full particulars in our next. LONDON: Printed and Published by James Bounsall, at the Mechanics' Magazine Office, |