iron ore, the joints being filled with a grouting of iron ore and lime. The yield in sound ingots is from 76 per cent. to 80 per cent. of the material charged, and the loss by oxidation from 12.6 per cent. to 16.5 per cent. Trials of the method have also been made at Nadjeshidinsk works in the Ural with an ore similar in composition to that of Karnowatka, about 40 per cent. of lime being required, as it is rather siliceous, about 24 per cent. of ore is necessary for the complete decarburizing of the pig-iron. As the blast-furnace was not at work the metal was added cold to the mixture of lime and ore, which was rendered perfectly fluid in 1 hour and 10 minutes. In this way the reaction, which begins as soon as the first portion of the ore is melted, is less violent, and a smaller furnace can be used than with direct metal from the blast-furnace. The largest proportion of ore used was 30 per cent. of the weight of the pig-iron, and 16.38 per cent. of dolomite, of which amount 12 28 per cent. was required for fluxing silica and 3.9 per cent. for alumina.

H. B.

New Forms of Heating Furnaces at Witkowitz, Moravia.

(Stahl und Eisen, vol. xviii., 1898, p. 988.)

These furnaces have been introduced by the inventor and manager of the works, Mr. Pietzka, for heating steel ingots and armour plates at Witkowitz. They are intended to combine the advantages of the Siemens system with a simpler form of construction by continuous heating without reversal of the direction of flame. The working part of the furnace between the fire-place and the flue-end is made movable by mounting it on a central pivot forming the ram of an hydraulic press, so that when lifted clear at the ends it can be turned half round when it is desired to bring the work charged at the flue-end into the hotter region near the fire-bridge. Gas firing is used, the coal being gasified in two producers 3 feet 9 inches square and 8 feet 4 inches deep, with forced draught produced by a Körting aspirator worked with air at 45 lbs. pressure instead of steam. The gas, delivered at a heat of about 900° C., is burnt by air previously brought to a strong heat by passing it through a "recuperator" formed of fire-clay pipes of square section, arranged in two blocks each of 120 pipes in the flue leading to the chimney, which is placed at right angles to the body of the furnace. A further portion of the waste heat is intercepted by a boiler placed between the recuperator and the chimney. The furnace-bed, rectangular in form, is 16 feet 6 inches long and 8 feet 3 inches broad, with two working doors at opposite ends of the long sides, which serve for charging and drawing alternately at each reversal. The central hydraulic pivot is 22 inches in diameter. The consumption of coal is 56 cwt. per shift of

12 hours for a production of 12 tons when in use for welding wrought-iron piles, or 22 tons when reheating steel blooms of 3 cwt. to 4 cwt. for the finishing rolls.

A furnace of the same class is used for reheating armour plates between the forging-press and the rolling-mill. It differs principally from that previously described in the arrangement of the recuperators, which are in line with the long axis of the furnace. There are three gas-producers, each 4 feet square and 9 feet 6 inches deep; and the recuperators, arranged in two rectangular blocks, contain 1,620 feet of clay pipes, giving a heating-surface of about 1,800 square feet. The furnace-bed, 29 feet long and 13 feet 3 inches broad, is carried by a plate-frame somewhat similar to a locomotive turntable upon a central ram 43 inches in diameter, the overhanging ends resting upon stops when the furnace is in position. There are four charging-doors, with a clear aperture of 32 inches square on the long sides, which are opened and closed by racked rods and pinions like those of the Bessemer converter. The coal consumption is 6 tons in 12 hours when heating a pressed armour-plate block of 30 tons, which requires about 24 hours to bring it up to the proper temperature for the rolling-mill.

H. B.

The Electric Driving of Accessory Machinery in Rolling Mills. MAX MEIER.

(Stahl und Eisen, vol. xviii., 1898, p. 1028.)

In a new girder rolling mill at Micheville Villerupt electric motors have been adopted for working the live roller trains of the mills, the charging cranes for heating furnaces, saws and finishing machines, carriers to the hot beds, and the machinery in the roll turning and fitting shop. The mills, which are arranged with their axes in the same transverse line, include a cogging mill with a clear length of 38 metres to the hydraulic bloom shear, and four roughing and finishing trains driven by a three-cylinder reversing mill at one end of the line, the cogging-mill engine being similarly placed at the other end. The power produced in a central station by three 250-HP. tandem compound condensing engines, directly coupled to the dynamos and making 85 revolutions per minute, giving a current of 450 volts tension, is distributed to the different motors in the following manner :

An electro-motor, of 110 HP., drives the bloom feeding rolls and the front and rear part of the girder mill. A second, of 150 HP., adjacent to the large three-cylinder mill engine, drives the feed rollers of the third and fourth pairs of the mill and the carriers for shifting the work sideways from the roughing to the finishing pairs. The two saws are driven each by an electro-motor of

80 HP., and their roller trains on either side by one of 60 HP., and the carriers to the hot beds are served by another of 75 HP. Besides these the fan blowing the gas-producer takes 25 HP., a billet shear and delivery train 75 HP., and the cold finishing machines 150 HP. In addition to these there are two of 60 HP. in the roll turning shop. In all cases the grouped machines are driven by belts from the electro-motor and the reversing is done by hand-gear. The power actually consumed by these machines during the working of the mills varies very considerably. With a constant tension of 450 volts the amount of current varies from 30 to 200 amperes, or from 18 HP, to 122 HP. Detailed examples are given of observations made during the rolling of joists 9 inches high from blooms weighing 30 cwt., requiring an average time of 327 seconds for passing through the mill.

DYNAMO No. 1.-DRIVING THE TRAVERSERS AND DELIVERY ROLLERS OF THE FINISHING TRAIN.

DYNAMO No. 2.-DRIVING THE FEED-ROLLERS OF ROUGHING TRAIN.

From five to six saw-cuts are made through each bar, each consuming about 75 to 80 amperes for 10 seconds, except in the last two, when the metal has become harder by cooling, and 89 amperes are taken for about 14 seconds.

The maximum current required by all the machines is summed up as follows:

The power supplied by the central station under ordinary conditions, with two of the three generators at work, varies between 400 and 700 amperes.

H. B.

The Influence of Arsenic on the Mechanical Properties of Steel.

J. MARCHAL.

(Bulletin de la Société d'Encouragement pour l'Industrie Nationale, 1898, p. 1336.)

Though this subject has already been studied by previous investigators, the results recorded have shown considerable discrepancies, and hence the Author has judged it expedient to undertake further experiments. The steel he employed was obtained on a basic hearth by the Martin process, and he directed his principal tests to ascertain the effect of arsenic on the welding properties of the metal. The manner of taking the samples at the time of running the steel from the crucibles is explained. The Author introduced into the ingot-moulds the necessary quantity of arsenic, and in each case took simultaneous samples of the steel unalloyed for the sake of comparative tests. The mode of analysis is set forth, and the various percentages of arsenic present, from 0.02 per cent. up to 2.75 per cent., together with full analyses of each sample, are shown in a Table. Plain tests and welding tests were made of each sample, except in the case of the highest percentage of arsenic, which would not weld at all. In all cases over 0.2 per cent. it was necessary in welding to employ a flux of borax, sal ammoniac, &c. As the percentage of arsenic rose the tensile strength increased, but the percentage of elongation fell off almost in direct proportion. When a certain limit was reached

the steel broke like cast iron with a very low strain. It seems probable that the arsenic behaves in the same way as aluminium and sets free a portion of the carbon in the form of graphite. Anyhow, this appears to be the case, judging from the texture of the fractures. In conclusion, the Author states that arsenic, when present in the small quantities usually found, does not interfere with the metallurgical uses of the steel. The discrepancies in the results previously obtained are, he thinks, probably due to the other impurities present in the steel, since arsenic would tend to intensify, along with these other substances which might accidentally be included, the defective quality of the metal.

G. R. R.

The Magnetic Properties of Nickel Steel.

EUGENE DUMONT.

(Archives des Sciences Physiques et Naturelles, Geneva, vol. v., 1898, pp. 331

and 426.)

In 1889 Dr. J. Hopkinson discovered that steel containing 25 per cent. of nickel is scarcely magnetic until cooled to a temperature of -40° C. After exposure to cold it remains magnetizable at ordinary temperature, and does not revert to its original condition until heated to about 600° C.

In 1897 Guillaume showed that these nickel-steel alloys may be divided into two classes, namely the reversible, which lose their magnetic properties on heating and recover them at the same temperature on cooling, and the non-reversible, comprising alloys containing 25 per cent. or less of nickel which exhibit the phenomena discovered by Dr. Hopkinson. The Author has determined the permeability at temperatures between -78° C. and +250° C. of twelve samples of nickel steel in a field of from 14 C.G.S. units to 50 C.G.S. units. The method employed was that of Ewing. The magnetizing bobbin was wound with bare copper wire, 1 millimetre in diameter with a distance of about 1 millimetre between each turn, the layers being insulated with asbestos paper and powdered asbestos.

1

For the experiments at high temperatures the coil was enclosed in a hot-air bath, heated by gas; and for low temperatures it was put in a zinc case surrounded by a freezing mixture. The nickel steel was used in the form of wires of from 0.4 millimetre to 1.0 millimetre in diameter. Full details of the experiments are given, and the results are also expressed in the form of curves. Author arrives at the following general conclusions. An alloy containing 22 per cent. of nickel and 3 per cent. of chromium showed no trace of magnetism even at the lowest temperature. Another alloy of 35.7 per cent. nickel containing chromium lost

1 Ewing and Klaassen. The Electrician, 15 May, 1891.

The