cleavage planes, and it is then termed spiegel-eisen. The variety known as ferro-manganese is a hard, crystalline body, but the fractured surface does not present the large cleavage planes so characteristic of spiegel-eisen. It contains from 20 to 85 per cent manganese. For further information see the author's work on Iron and Steel Manufacture (Macmillan).

§ 179. Iron and Nickel.-These metals unite together to form a series of alloys which have lately received a good deal of attention; and although the most recent productions contain small quantities of other metals, such as manganese, they will be considered under this heading. Certain native alloys, occurring in aerolites, contain from 3 to 10 per cent of nickel. Faraday and Stodard prepared alloys of iron and nickel containing 3 and 10 per cent of nickel respectively. The former appeared to be as malleable, and could be as easily worked as pure iron. The latter was semi-ductile, very tenacious, with a granular fracture, and little affected by the atmosphere. They are capable of a high polish. Bergmann states that iron and nickel combine in all proportions. Lampadius states that an alloy of 5 parts nickel and 2 parts iron is moderately hard, easily malleable, and has the colour of steel.

Mr. James Riley of Glasgow and Mr. Hall of Sheffield have independently given considerable attention to ironnickel alloys, and in a paper read by the former gentleman before the Iron and Steel Institute in May 1889, the following facts were stated: "The alloys can be made in crucibles or on a large scale in the Siemens's Open Hearth furnace, where a charge can be worked off in about seven hours. Its working demands no special care, and the composition of the resulting steel is easily and definitely controlled. If the charge is properly worked, nearly all the nickel is found in the steel, and almost none in the slag. The metal sets steadily in the mould; it is more fluid than ordinary steel when melted; it sets more rapidly, and

appears thoroughly homogeneous. The ingots are clean and smooth in appearance on the outside, but those richest in nickel are a little more piped than are ingots of ordinary mild steel. There is less liquation of the metalloids in these ingots, therefore the liability to serious troubles from this cause is much reduced. The scrap produced in hammering, rolling, shearing, etc., can be remelted in making another charge without loss of nickel.

"If the steel has been properly made, and is of correct composition, it will hammer and roll well, whether it contains little or much nickel. It must be remembered, however, that in nickel-steel we have present nickel, manganese, and iron; with carbon, silicon, phosphorus, and sulphur, and that a difference in quantity of some of these will influence the character of the alloy; in other words, the degree of purity of the nickel and iron employed will modify the result, as in the case of ordinary iron and steel.” The following table embodies the results of tests on various alloys made by Mr. Riley :

It will be seen from the foregoing table that the addition of nickel to mild steel increases the elastic limit and breaking stress considerably. In Nos. 2 and 5 tests the extreme hardness, partly due to the large amount of carbon, is also increased by the presence of nickel. In No. 9 test, with much less carbon, but with 10 per cent nickel, a very hard alloy is obtained. This quality of hardness continues as the nickel is increased, until about 20 per cent is reached, when a change takes place, and successive additions of nickel tend to make the steel softer and more ductile. With regard to the hardening effect of nickel on iron there is some resemblance to the manganese-steel previously described. The whole of the series of nickel-steels up to 50 per cent nickel take a good polish and finish, with a good surface, the colour being lighter with the increased additions of nickel.

Mr. Riley states that the steels rich in nickel are practically non-corrodible, and that those poor in nickel are much better than other steels in this respect. The 1 per

cent nickel-steel welds fairly well, but this property deteriorates with each addition of nickel. Mr. Hall states that the alloys of nickel and iron are among the most powerful connected with the magnet that he has seen or heard of. The conductivity for electricity of iron-nickel alloys is extremely low, and the electric resistance extremely high.

The alloys of iron and nickel may be prepared by melting iron and nickel together; by reducing oxide of nickel with carbon in the presence of iron; or by adding ferro-manganese to molten iron and nickel to obtain nickel-steel. Mr. Riley states that without the aid of manganese the conditions of treatment would not be successful.

$180. Iron and Cobalt.-According to the experiments of Brande and Bergmann, these metals combine in all proportions. The alloys are said to be hard, and as ductile as iron. Hassenfratz has shown that iron containing cobalt can be forged and welded, and although a little brittle when hot, it is not so when cold. According to Berzelius, the

alloys of these metals are hard and magnetic. It is probable that the action of cobalt on iron is much the same as that of nickel, judging from the similarity of cobalt to nickel in many of its physical and chemical properties.

§ 181. Iron and Molybdenum.-Dr. Thompson considers that of all the metals, molybdenum is the one with which iron unites most readily. With equal parts of the two metals the alloy is fusible with the blowpipe. With 1 part iron and 2 parts molybdenum, an alloy of a clear grayish-white colour is obtained. An alloy of 20 per cent molybdenum is whiter than iron, very hard, brittle, tenacious, and has a granular fracture. Berthier considers the alloys of molybdenum and iron to be in every respect the analogues of those of tungsten and iron. They are generally grayishwhite, hard, brittle, fine-grained, and magnetic. When the molybdenum is below 50 per cent the alloys are somewhat fusible. Copper blast-furnace bears (as the metallic masses found in the hearths of old copper blast-furnaces are termed) chiefly consist of iron and molybdenum.

§ 182. Iron and Chromium.-These metals have a strong affinity for each other and appear to form alloys in all proportions. Chrome-iron ore is somewhat abundant in nature, and when such ore is submitted to a reducing influence at a high temperature both iron and chromium occur in the reduced metal. Berthier states that when a mixture of oxide of iron and oxide of chromium is strongly heated in a carbon lined crucible, both oxides are completely reduced, and a perfectly homogeneous combination of the two metals is obtained. The alloys are generally hard, brittle, crystalline, of a grayish-white colour, and having a considerable lustre; less fusible, less magnetic, and less soluble in acids than iron; the characters are the more prominent in proportion to the amount of chromium present in the alloys. 1 In 1820 Faraday produced two specimens of chrome

1 Quarterly Journal of Science, 1820.