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trials by stripping stress. Second, that the cold- punched nuts exhibited a strength never attained by the hot-pressed nuts, but that such variations in the strength of both styles occurred as to have caused the hot-pressed nuts to equal, and occasionally to excel, in strength the weakest specimens of cold-punched nuts."

IRIDESCENT GLASS.

Some interesting results of experiments upon the artificial production of the iridescent glass of the ancients, so highly prized by antiquarians, have been reported by two French chemists, MM. Frémy and Clémandot. These investigators ascertained by observation that glass, when subjected to conditions which determine its gradual decomposition, becomes covered with slender lamina which present the remarkable phenomenon of irisation. They have succeeded, according to account, in producing this irisation on glass so that it shall present the peculiar appearance of mother-of-pearl, by submitting it, under the influence of heat and pressure, to the action of water containing 15 per cent. of hydrochloric acid. Only certain kinds of glass, however, are suited for this treatment, and the conditions of composition as well as those of annealing affect the result.

It is not improbable that this observation may be the initial step to the restoration of "a lost art" or the establishment of a new one. The products of this new manufacture -ornamental vases, cups, bowls, etc.—which appear to have already been placed upon the market abroad in considerable quantity, though very beautiful, are said to be as yet much inferior to the Assyrian or Egyptian iridescent glass, in the production of which time is held to be an important factor.

MISCELLANEOUS.

Some attention was attracted among iron-workers by the announcement of the discovery, by Professor Barff, of a method by which iron may be effectually prevented from rusting, and, "however much exposed to the weather or corrosive vapors or liquids, rendered practically indestructible and everlasting." The process in question consists, substantially, in subjecting the iron to the action of superheated steam, whereby it acquires a thin but firmly adherent coating of magnetic

oxide, which, it is affirmed, by its great indifference to atmospheric and chemical agencies, effectually protects the underlying metal from further change from these causes. Dr. Percy has confirmed the importance of this method; and, in a paper read before the last meeting of the British Iron and Steel Institute, laid down the general proposition that the most effectual mode of protecting metals from atmospheric action is to impart to them "a coating of their own oxides respectively." This very rational generalization he demonstrated to be correct in the cases of iron, copper, and lead.

A new process of electroplating, which may become of great utility, has been described in Silliman's Journal, by Professor A. W. Wright, of Yale College. It is based upon the fact that the various metals may be volatilized by the electrical current. He provides a hollow vessel, from which the air has been partly exhausted, and arranges therein at proper distances apart the poles of an induction coil-the article to be electroplated being suspended between the poles. The negative pole carries a small piece of the metal that is to be deposited, and a battery of three to six or any number of cells is employed as may be necessary. The metal volatilized by the spark is condensed on the cold surface (glass, etc.), forming a firmly adherent, brilliant, and uniform coating. The invention has already been successfully applied in practice, and promises to become valuable.

The prize offered by the Prussian Minister of Commerce and Industry for a method of preparing plaster casts so that they may be washed when necessary without impairing their sharpness, was lately awarded to Dr. Reissig, of Darmstadt, who offered the following suggestions: 1st, to convert the sulphate of lime into the sulphate of baryta by washing the surface with strong baryta water; and, 2d, to convert the sulphate of lime into silicate by the application of silicate of potassa. The object to be attained is to form a surface which shall not dissolve in water and shall prevent dust from entering the pores. The above methods of treatment render plaster casts indifferent to the action of hot water and soap, but leaves them porous and capable of retaining dust, so that an additional treatment is necessary to remedy this defect. This consists in the application of an

alcoholic soap solution, which, on evaporating, leaves a layer of soap on the surface effectually stopping up the pores.

From the official decree of the Superior Council relative to the matter of awards at the coming Exposition in Paris, it appears that the sum of 1,500,000 francs has been appropriated for that purpose, which sum will be awarded and distributed by a jury composed of three hundred Frenchmen and three hundred and fifty foreigners. The foreign jurors are selected by their respective governments, and those of France by the Superior Council. This international jury is to complete its work between June 1 and September 1, 1878, inclusive. The distribution of awards is fixed for September 10, 1878. The rules and regulations for the government of the jury are the same as those of the Centennial Exhibition of 1876.

INDUSTRIAL STATISTICS.

By WILLIAM H. WAHL, Ph.D.,
PHILADELPHIA, PA.

The following compilation from the carefully collected statistics of the American iron trade for 1876 is made as nearly as possible uniform with that published in our last year's Record, to render comparison easy:

PRODUCTION OF PIG-IRON IN 1876.

The secretary of the American Iron and Steel Association reports that the production of pig-iron in the United States in 1876 was 2,093,236 net tons (a very slight variation from his estimate as furnished to our last), against 2,266,581 tons in 1875, 2,689,413 tons in 1874, 2,868,273 tons in 1873, and 2,854,558 tons in 1872. A comparison of these figures shows a decrease in 1876, as compared with 1875, of 173,345 tons, or about 8 per cent. Commenting upon his figures, the secretary says: "Since 1873 - the year of greatest production each year has shown a decrease as compared with the preceding years, the percentage of decrease being as follows: 1874, 6 per cent.; 1875, 15 per cent.; 1876, 8 per cent. From 1873 to 1876 the decrease has been 775,042 tons, or 27 per cent. This is a very great shrinkage, and indicates, with concurrent low prices, a very great depression in the pig-iron industry of the country. If the rate of decrease which marked the period from 1873 to 1876 were to be continued, the production of pig-iron in the United States would entirely cease in 1884-less than eight years from the present time; and our furnace-stacks would only be useful as observatories for the study of astronomy."

The secretary does not admit, however, that things are so bad as they at first appear, and points to the marked diminution in the percentage of decrease in 1876 as compared with that of 1875, and to the decided diminution of stocks on hand and unsold at the close of 1876 (106,110 tons less than

at the close of 1875), as strong symptoms of an early increase in the manufacture of American pig-iron. This judgment is confirmed by the following statement, politely furnished by the secretary to the writer, giving his estimate of the production of pig-iron during the year 1877, to wit: "This year [1877] we will make a little more pig-iron than last year— probably 2,200,000 net tons. The other items of production. will stand about the same in 1877 as in 1876."

Of the total production of 1876, 794,578 tons were smelted with anthracite coal, 990,009 tons with bituminous coal and coke, and 308,649 tons with charcoal. The whole number of completed furnaces in the country at the close of 1876 was 714 (against 713 in the preceding year). Ten new furnaces were built in 1876, and 9 old ones were abandoned. Of this total of 714 furnaces at the close of 1876, 236 were in blast and 478 out of blast. Of the product of 1876, Pennsylvania made 48.2 per cent. and Ohio 19.2 per cent., both increasing their percentage of production as compared with the preceding year. The other iron-making states, with few exceptions, decreased their production as compared with 1875.

CONDITION OF BLAST-FURNACES OCTOBER 1, 1877.

For comparison with a similar statement given in last year's Record, we append herewith a summary of a detailed statement published by the Iron Age of New York, showing the condition of the blast-furnaces of the United States on October 1, 1877:

Number of charcoal-furnaces in blast (weekly capacity 7887 tons).. Number of charcoal-furnaces out of blast (weekly capacity 12,957 tons).....

Number of anthracite-furnaces in blast (weekly capacity 17,067 tons) Number of anthracite-furnaces out of blast (weekly capacity 25,268 tons)....

89

176 86

140

Number of bituminous or coke furnaces in blast (weekly capacity 19,670 tons)....

77

Number of bituminous or coke furnaces out of blast (weekly capac

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A comparison of these figures with those of the preceding

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