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made of the shops in which the table glass and Bohemian crystal is cut, to which is also annexed the store house for the finished glass.

Melting Furnaces.-As the beauty and quality of the glass, other things being equal, depends particularly upon their perfect fusion, which takes place only at a very elevated temperature, not to be obtained except by a particular arrangement of the melting furnace, (schmelzöfen,) this becomes the most important part of the establishment. This furnace should be so constructed, that, Ist. A suitable and sufficiently elevated temperature may be produced; 2d. That the flame may circulate freely around the glass pots; 3d. So that the greatest useful effect may be obtained with the smallest quantity of fuel.

These conditions have led to the adoption of peculiar furnaces of an elliptical form, furnished with shelves on which the glass pots are placed. These furnaces are all nearly of the same form; but their dimensions are somewhat variable with the number and size of the pots; they hold 7 or 8. The fire-bricks which are used in the construction of these fornaces, are formed of two parts by volume of fireclay mixed with one part of the fragments of glass pots, picked and powdered. The vault is always made of a single piece of clay.

Annealing Furnaces. These furnaces are always accompanied by a kühlofen, or furnace for annealing the glass heated by means of the flame which escapes from the melting furnace. The annealing furnace is almost always surmounted by an apparatus for drying the wood, which is composed of four cubic boxes of cast-iron, 2.89 feet on each side, exposed on five of their sides to the flames which come from the annealing furnace by four apertures, and afterwards escape from the apertures by a single opening in the upper part.

The operation is conducted far too rapidly, for a complete drying, and even an incipient roasting of the wood is obtained in the course of one and a half, or at the most, two hours; and it would be evidently very advantageous to slacken it by furnishing the openings which communicate with the annealing furnace with movable registers.

The length of the season is, upon an average, twenty-eight weeks, or six months.

Glass Pots.—The glass pots (hafen) used in Bavaria, are circular, and made with the greatest care; they are of two dimensions, and have no rims.

The sinallest receive a charge of from 140 to 165 lbs. of fritted materials, and are used in the manufacture of fine glass, and table glass. Their dimensions are as follows:

above Internal diameter,

1.28 feet. below

1.11
above

1.47 "
External
below

1.38 €
Depth,

1.44 « Thickness at bottom, ; .

1.57 inches. The large pots receive a charge of about 220 lbs. avp., and are used in making window and bottle glass; their dimensions are as follows:

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Internal diameter, {

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at the mouth,

1.41 feet. at bottom,

1.25
at the mouth,

1.67
External
at bottom,

1.57
Depth,

1.7 Thickness at bottom,

1.87 inches. The paste of which these pots are made is composed of a mixture of very aluminous fire-clay, of which I have given the analysis above, and of very pure quartz pulverized in a dry state ; sometimes they employ, as a cement, the remains of old glass pots broken up and picked, and then pulverized. Aster kneading the paste with the feet, in order to make the mixture as thorough as possible, the pots are formed by means of a small wooden beater, and a mould also of wood, which allows the workmen to give them accurately the same exterior dimensions. These crucibles last very differently; at Swartzthal, they last, upon an average, six weeks; at Silberberg, Winterberg, Leonorenhain, about twelve, or sixteen, weeks, and sometimes more. These crucibles after having been sufficiently dried in the air, are baked in the annealing furnaces, or very rarely in a separate furnace. When a change is necessary, they introduce them during the working season, by one of the embrasures which is made of sufficient size for this purpose, and larger than the others. Of course the new crucibles are brought up to a white heat before being placed upon the furnace shelf.

The analysis of a selected fragment of the glass pots lised at Silberberg, gave me-Silica,

61.0 Oxygen, 31.7 Ratio, 3 Alumina, 39.0

10.8

1 Oxide of tron, a trace.

a

66

66

100. Very white particles, which appeared to be small grains of quartz, could be seen with the naked eye in the paste.

Another Bohemian glass pot, whose locality is unknown, gave M. Berthier, upon analysis, Silica,

68.0 Oxygen, 35.4 Ratio, 4 Alumina, 29.0

8.1 Oxide of iron, 2.2

.6 9.

1 Magnesia, 0.5

.3

66

}

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99.7 By use the substance had become excessively hard, of a light gray, and was filled with an infinity of small globular cavities, which indicated a commencement of fusion, and presented besides a multitude of small very white grains, which showed themselves very plainly upon the grey ground of the mass.

Flattening Kilns.—These kilns are either isolated or placed together two by two; I have been informed that there are some placed together in fours. They are always composed of a flattening kiln, (strecköfen) into which the flame comes from the fire-place by four small chim

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neys, placed at the end of the bottom of the kiln, and which communicate with an annealing furnace, into which the lame passes from the fire-place by a single opening only.

Of the Persons Employed. The persons employed in a glass works consist, Ist. Of a director, (buchhatter) who superintends the works, keeps the books, receives orders, forwards the goods, pays the workmen, &c.

2d. Of the workmen employed in transporting and preparing the raw materials.

3d. Of women who are employed to pack the finished goods. 41h. Of workmen employed in transporting the goods.

5th. Of workmen employed in the making and cutting of the glass. Among these are the firemen, the glass-blowers and glass-cutters.

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 per week, or about 20 cts. 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 92 cents per shock of glass worked. The number of pieces which form a shock, varies according to their nature, and the rate is so arranged, that a good workman may easily gain $1 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 labor or m.anorial 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.1 shall give here the annual consumption of fuel in each establishment, supposing it to consist, as is usually the case, of iwo 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 (192347 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 (144512 cubic fect, in making table glass, and fine glass, which gives an economy

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 vaporize it entirely, and that in Silberberg this heat is taken from that developed in the melting furnace, while in the works of MM. Meyer, Vo. IX, 3RD SERIES—No. 2.–FEBRUARY, 1845.

11

of tó

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 cub. ft. per day, or 1143 cords per year, (146578 cub. ft.,) a result which accords in a remarkable manner with that obtained from the works of Winterberg and Leonorenhain.

To be Continued.

FOR THE JOURNAL OF THE FRANKLIX INSTITUTE.

Mathematico-Physical Class of the Royal Bavarian Academy of

Sciences, at Munich.- Translated by Dr. H. SCHOLL. A prize of one hundred ducats is promised to the successful competitor, for a prize essay on the following subject,—the Atomic Weights of Sulphur, Iron, and Copper, are to be stated in unities of Oxygen, so that each of these atomic weights be derived exclusively from all the combinations with the other elements mentioned. A sufficiently large number of individual observations is to be made according to every method, in order to obtain a tolerably sure average value, and to find the variation of every experiment from the mean. All the results of weighings are to be reduced according to the method and table of Bessel, to the weight in the vacuum. From all the different series of observations are to be deduced, regard being paid to the relative value of the different methods, the most probable values of the elements mentioned, together with the limits of certainty of their determination according to the method of the least squares. The observations are to be communicated in their original form, so that every number that has an influence upon the result, may be traced back to the original setting down of the experiment.

The reasons that have induced the Academy to the proposition of the foregoing subject, are the following: In calculating chemical analyses by atomic weights, principally in examining organic substances, it happens frequently that the difference between the calenlation and the observation is greater than could have been presumed from the accuracy with which the observation had been made. In complicated combinations, by atomic weights, doubts even may remain wheiher the one numerical ratio, or the other next to it, comes up closer to the observation. This difference arises in part from errors committed in the experiment, in part also from the uncertainty of the determinations of the atomic weights. The uncertainty of the different atomic weights, however, being itself varying, and increasing with their number in the combinations, may have great influence on the result, though the error in the determination of the simple atom be but very slight.

In order to enable us, therefore, to distinguish what share the determination of the atomic weights may have in the difference between the calculation and the observation, and to see whether the analysis is included within this and its own uncertainty, it is requisite not only to have an accurate knowledge of the atomic weights themselves, but to know also how far their determinations may possibly deviate from truth.

The atomic weights have indeed been derived from a great number of observations, part of which had been made with great care, and very considerable improvements in their determination might be obtained, if, from all the observations made, those values were derived by calculation, that approach the nearest to all the experiments; yet the different methods of determination rest on observations of too unequal value to allow us to expect an entirely satisfactory result from the result of this important work.

This it is which has induced the Academy to set a prize on the making of new and most accurate possible determinations, in order to lay thereby the foundation for a thorough and comprehensive establishment of the atomic weights, and of the limits of their certainty. The four elements mentioned have been chosen in preference to others partly on account of their being frequently used, and capable of useful application, partly because two of them enter mutually into different fixed combinations, and may furnish, therefore, different series of equations of condition. The atomic weights forming, moreover, iminutable proportions in nature, it needs no farther explanation of the scientific value of their most thorough possible examination.

Competitors for the prize have to send in their essays, written in either German, French, or Latin, and provided with a motto, and a sealed note containing the author's name, before November the 1st, 1845, to the Royal Academy of Sciences, at Munich. The decision as to which of the essays sent in, the prize shall be due to, will be given in the public session of the Academy, March 28th, 1946.

FOR THE JOURNAL OF THE FRANKLIN IXSTITUTE.

Regulation of Paper Machines. It is found in practice to be difficult to regulate the motion of the Foudrinier, and other machines, in common use, for the manufacture of endless paper. When the flow of pulp upon any machine is uniform, an acceleration of its motion will make the paper thin, whilst a retardation will make it thick. Hence it is of the utmost importance, in order to make paper of even weight and thickness, that when the flow of the pulp is uniform, the machine shall move uniformly at the same speed. But if, by any contrivance, the flow of the pulp could be augmented, or checked, just in the same proportion as the machine moves slower, or faster, it is evident that the necessary relation between its speed, and the quantity of pulp thrown on, might be effected and maintained. Consequently, two modes of obtaining the requisite uniformity in the thickness and weight of the endless sheet of paper suggest themselves.

1. To regulate the speed of the motor driving the machine. II. To regulate the flow of pulp upon the machine.

The attention of constructors has usually been directed chiefly to the first method ; and hence we find the machine wheels of paper mills are very frequently tub-wheels, wasting a large amount of water, but nevertheless selected and used on account of the regularity of

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