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In front of each range of drying-chambers there is a small railroad, extending from the melting-room to the warehouse. An iron car takes the prepared composition, and carries it to the drying-chambers in succession. Before each door or station, an orifice, o' o', made in the floor, exerts a powerful draught, which draws the vapors into the exterior lateral tunnel. The dipping is quickly done, and the frames are immediately placed in the drying-chambers, the iron doors of which are carefully closed.

The middle portion of the building is reserved for boxing. Under the tables are also placed ventilating-openings, o" o". The filled boxes are finally put in the car and carried to the warehouse.

The main passage-ways c c and c' c' enter separately into the base of the chimney, and are kept apart there by small vertical walls, in order to prevent contrary currents and to allow them to be regulated at will. By means of these arrangements, all smell of phosphorus in the main factory is prevented, and the men who work there are no longer exposed to necrosis. By taking the additional precaution of having them frequently visited by physicians, and of maintaining proper rotation in the hands employed in the different shops, they will be completely freed from this terrible disease.

MANUFACTORIES.

72. In some manufactories, it is essential for the quality of the products that the internal temperature be not allowed to fall below a certain limit; or, in other words, that the manufactory be heated even in spring and fall, and that the windows be kept closed. From this it follows that the air, not being changed, becomes gradually saturated with vapors and cutaneous emanations, and becomes at last unhealthful.

The workmen being thus kept continually perspiring, although they take off part of their clothing, go out afterward into the cold air, and often contract serious affections of the respiratory organs.

The conditions of the manufacture may be secured at the same time with those of hygiene by a strong ventilation, which shall constantly furnish fresh air of the necessary degree of temperature and even of moisture while regularly carrying off the foul air. With this change of air, a temperature of 750 or 77° will be found comfortable, and the workmen no longer be continually perspiring in an atmosphere constantly becoming more impure.

The rules to be observed are the same as those mentioned before, and a complete change three or four times an hour will usually be sufficient. The escape-steam from the engines is in such cases usually employed for heating, and it may be so regulated as to give the desired temperature to the fresh air, and the smoke-stack of the steam-engine will, without additional expense, maintain the draught required for carrying off the foul air.

In cases where the smoke-stack would be otherwise too small, the

draught may be increased or entirely produced in it by heating it by steam, or by placing a steam-jet in it as in a locomotive.

73. Workshops in which dust more or less dangerous to breathe is produced. In a large number of occupations, the division of the raw materials produces dust, which may be fine or coarse, heavy or light, harmless or injurious, and which it is important to remove from the workman and carry out of the building.

In most of these cases, ventilation, by means of a draught produced by heat, would be insufficient, at least unless it were made extremely powerful by an intense heat. It would be sufficient for light dust of very finely-divided materials, but for heavier dust, such as that produced by grindstones, it becomes necessary to use mechanical apparatus to force, through suitably-arranged pipes, currents of air at a proper velocity, which trial alone can determine.

In winter, when artificial heat may be required, as well as in summer, when it is unnecessary, it is essential that the discharge-openings should be placed as near as possible to the machines which produce the dust or emanations, and that the openings for admission of fresh air should, in general, be far off, in order that the velocity should gradually increase from the point of admission to that of exit.

But if the shop contain few workmen, if it is naturally sufficiently well aired, and if it is only required to carry off the dust as directly and quickly as possible, it would be better that the air be admitted under the cover which should completely surround the apparatus or the machine above the point where the dust is produced, while the draught is applied below the same point and the dust is carried directly out of the building. The preceding remarks apply especially to those shops in which but a few detached instruments are used.

74. Cutlery-works.-One of the most dangerous occupations is that of the cutler. When proper precautions are not taken, the dust arising from the grindstones, which are used dry, enters into the respiratory passages.

These dangers are reduced and almost removed by the following arrangements:

75. Grindstones used wet, (Figs. 23, 24.)-The stones should be sur

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The passage intended for carrying off the dust should be placed underneath the stone, and beyond the point where the work is applied,

regarding the direction of the motion. It should have a breadth a little greater than that of the stone, and a depth of eight inches, at most, for the largest stones. A sliding door serves to close it whenever dry dust is not produced. The water-discharge pipe should also have a valve, which may be closed when water is not used, and when it is desired to carry off the dust produced when the stone is trued.

The separate air-tubes from each

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stone lead to a collecting-pipe 16 inches by 12 inches, to which they are united by couplings.

If there are only four or five stones in the works, a single collectingpipe will be sufficient, and the blower should be placed at the end. But if there are eight or ten stones in one line, it will be better to place a second collector, 16 inches by 12 inches, in the middle of the length of the first, and perpendicular to its direction. The blowing-apparatus should be placed in the extremity of the second pipe.

Finally, if there are two long parallel rows, with eight or ten stones in each, they should also be connected with the second collector, or with a third, 16 inches by 20 inches, communicating with the ventilator.

In all these arrangements, movable valves should be placed at the junction of each of the pipes, to prevent the circulation of air in those which are not used at any time for carrying off the dust, since it is not intended to ventilate at the same time all the stones of the same mill. The valves placed at the head of each pipe should also be closed when it is not being ventilated.

But the greatest difficulty in rendering these places healthful, as in most other cases, arises from the carelessness of the workmen, and in the negligence of the foremen, who do not insist on the strict observance of the regulations.

76. Application.-At Châtellerault's armory, the results obtained by Peugeot & Bros., of Valentigney, (Doubs,) in their hardware manufac tory, were made use of, blowing-machines having been placed in two shops containing each

Main stones, 8 inches in diameter...
Grooving-stones, 4 feet in diameter...

2

16

18

A fan-blower, 31 inches in diameter and 16 inches wide, parallel to the axis, and having a central opening 11 inches in diameter, making 900

to 1,000 revolutions a second, and requiring at most 8 to 10 horse-power to run it, easily removes all the dust produced during the truing of the two main stones and twelve of the grooving-stones, the other passages being closed.

The axis of the fan-blower is placed in the line of the last collectingpipe, and is closed on the side opposite that pipe; the air carrying the dust is expelled at the outer circumference, which is entirely free.

Notwithstanding the success obtained in large works by the arrangements mentioned above, it would be better in all cases to separate the workmen into small shops of two stones each, each furnished with special ventilating-apparatus similar to that which we have described. Recent trials seem to show that ventilation obtained by forcing in air would in this case prove very satisfactory.

DRYING-CHAMBERS.

77. The general arrangements which should be adopted for dryingchambers are in conformity with the rules previously given. The air should flow in at the top; and, as in this case, it is always very hot, it enters of its own accord, but it is necessary that it should be introduced uniformly. The openings for the escape of the air saturated with moisture should be placed near the floor and on the whole circumference of the room. It is sufficient to connect the ventilating-pipes with the base of the chimney of the heating-apparatus.

The temperature which it is necessary to keep up in the dryingchambers depends upon the nature of the articles to be dried. For vegetable substances and flour, it need not exceed 105° or 1100; for linen and cloth, 158°.

The particular conditions in each application may lead to some modifications of the general rules. Linen-drying rooms present a case which it is well to specify.

LINEN-DRYING CHAMBERS.

78. The arrangements for these useful accessories (Figs. 25, 26) to large bleaching-establishments have been carefully studied by Bouillon, Muller & Co. The linen is carried to the wringing-machine, which removes from it a great part of the water which it contains after having been washed; but it still retains about one-third of the total weight when it reaches the drying-room. When it is hung vertically, this water accumulates principally at the lower part, which therefore becomes hard to dry. Again, when the air enters through a single opening at the upper part of the chamber, the interruption to the circulation of hot air caused by the linen which hangs in vertical bands and the force of the draught which tends to draw the air directly toward the ventilating-openings prevents the drying from proceeding uniformly, especially in large dry ing-houses. The observation of these irregular effects has led Bouil.

lon, Muller & Co. to adopt, for their latest linen-drying chambers, the following arrangements:

The chambers of which a drying-room is composed (Figs. 25, 26) are very small, and are at most 10 feet long, 4 feet wide, and 5 feet high, or 200 cubic feet in area.

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The floor is composed of two pieces of curved sheet-iron, forming at the same time the top of the warm-air chamber of the heater below. These two pieces of sheet-iron leave an opening o between them, which extends the whole length of the drying-room, and through which the hot air is introduced, which, after having dried the bottom and dampest part, rises with the vapor it produces toward the ceiling, and descends again to the ventilating-openings, arranged near the floor along the whole length of the side-walls, the latter being made hollow and provided with pipes leading to the chimney, which also contains the smokepipe, as shown in the figures.

The linen is arranged outside of the drying-chamber on brass tubes. sliding on iron rods extending the whole length of the chamber. These rods and the tubes which they carry are placed at the middle of a narrow door of the same height as the drying-chamber, which is only opened when the wet linen is put in, or the dry taken out.

Each chamber contains 8 rods. They receive, in two charges, 106

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