THE POPULAR SCIENCE MONTHLY.
Bridge or of the Eiffel Tower. If the engineers of those stupendous structures had had at their disposal a metal of forty tons strength and twenty-eight tons elastic limit, instead of thirty tons strength and seventeen tons elastic limit in the one case and, say, twenty-two tons strength and fourteen to sixteen tons elastic limit in the other, how many difficulties would have been reduced in magnitude as the weight of materials was reduced! The Forth Bridge would have become even more light and airy, and the Tower more netlike and graceful, than they are at present." And Sir Frederick Abel, in his presidential address at the Leeds meeting of the British Association, remarked, "It has been shown by Riley that a particular variety of nickel steel presents to the engineer the means of nearly doubling boiler pressures without increasing weight or dimensions."
On the other hand, it must be admitted that there are those who maintain that the future of nickel steel has been painted in too rosy colors. For example, in Stahl und Eisen for October, 1889, Prof. A. Ledebeer criticises the claims made for nickel steel, and predicts that the alloys of nickel and steel "belong to that class of inventions which crop up at intervals, finally to be buried in oblivion because of their impracticability." The criticisms of this German writer were practically answered by a report in some of the trade journals immediately after the appearance of his criticism, to the effect that there existed among steel-makers a demand for several thousand tons of ferro-nickel for use in the preparation of nickel steel; and trials of armor plate made by a board of United States naval experts at Annapolis, Md., have shown that nickel steel is superior to ordinary steel for armor plate. As a result of these tests the House of Representatives at Washington made an appropriation of one million dollars for the purchase of nickel for use in the manufacture of armor for the new armored war-ships.
Coming now to consider the source of the nickel of commerce, we find it is derived principally from two classes of ores—viz., a nickeliferous pyrrhotite and a silicate of nickel. A very remarkable deposit of the latter occurs in New Caledonia, one of the New Hebrides and a penal colony of France, and since the period when productive work was begun on these deposits it may be said that the New Caledonia mines have entirely controlled the market. The ore known as garnierite is a hydrosilicate of nickel and magnesia, and is found in beds of serpentine mixed with oxide of iron, chrome iron ore, and a little cobalt. It is especially valuable on account of its entire freedom from arsenides and sulphides. Similar ores occur on this continent—for instance, in North Carolina and Oregon—but these deposits have not been developed to any extent. The discovery of the New Caledonia deposits aroused great