"Strengflüssiger" or "Strengschmelziger"-than bisilicates:

The silicates of oxides of manganese and iron (protoxide) differ very little from each other.

The bi- and trisilicates of the different earths are formed

at a lower temperature.

Of the bisilicates those of barytes and lime form at

2100°

The temperature required for the formation of compound silicate (for instance, CaO3 Si2O3 + A103 Si203, a frequently occuring slag) from the earths composing them, is very much higher than that at which slags which have been already fused can be melted. As the slags coming from smelting processes are seldom formed by fusing together these independent components, but more frequently from a mixture of silicates already formed-partly from the ores, etc., and generally of manifold combinations of the oxides of the earths-the temperature required for the formation of the new slag or compounded silicates will lie between their point of fusion and the temperature which would be necessary to form this new slag from the separate simple substances.

Refractory slags "strengflüssige"-which are always indications of faulty working of the furnace, arise either from

insufficient temperature, or from injudicious combination of the charges, as when too much silica and too little of the bases, or the contrary, exists, or if among the bases there be an excess of alumina and magnesia. Such slags are recognized by their pasty nature, their earthy, half-fused appearance, and by the air-holes pervading them. On the other hand, the charge is a good combination when the slags flow out of a good consistency-as free from metal as possible-and when, for a given consumption of fuel, the maximum of ores can be used.

Dr. Percy, while objecting to the principle of Plattner's method-because it assumes that alloys of gold, silver, and platina fuse at the mean temperature of the component parts

-says we may accept his results as affording practical information of value. "The melting points of metals and their alloys are fixed and unvarying, except under extraordinary conditions of great pressure, and as they extend through a very wide range of temperature they may be conveniently employed in the determination and comparison of high temperature."*

Plattner himself considered that he had only determined temperatures correctly proportioned to each other, and not absolute thermometric limits.

This note is to explain what is meant by "Strengflüssige Erzen""minerais refractaire"-as used by continental

writers.

NOTE III. p. 87.

The beautiful inductive investigation of the large yield of pig-iron with small consumption of fuel in the Styrian and

*Percy, op. cit. vol. i. p. 48.

Carinthian furnaces, in section xliii. of Mr. Bell's work, is well worthy of study in reference to this conclusion of M. Ebelmen.

Also Dr. Percy, vol. ii. p. 446, quotes Ebelmen in detail as follows: "If we compare two kinds of fuel, which act with different rapidity upon the air and carbonic acid, such as coke and charcoal, it is very plain that it will be necessary to increase the mass of the least combustible of the two, relatively to that of the ore, in order that oxidation of the iron should not take place to a greater extent in one case than in another. Thus experience has proved that, on the average, twice as much coke (by weight) is required as charcoal to produce in the blast furnace pig-iron of the same amount and of the same quality. In the same manner may be explained the difference of consumption of the same furnace, working always with the same fuel, according as it is desired to produce different qualities of pig-iron. Thus, much more charcoal is consumed in order to obtain gray pigiron than white." Dr. Percy remarks-"There is no doubt about this fact, though there may be much as to Ebelmen's explanation of it." Dr. Percy's remark I do not agree with. The "fact" is open to the greatest doubt.

NOTE IV. p. 87.

The fact that charcoal decomposes CO2 (burns under a current of CO2 giving off CO) more rapidly than hard or soft coke, is proved incontestably by Mr. Bell's experiments, Nos. 818 and 819, p. 75, No. I. Part II. of Journal of Iron and Steel Institute.

NOTE V.

It is proposed in this Note to give a brief history of the "Theory of the Blast Furnace," with the view of showing how very recently correct notions on the subject were first published, even of the chemical phenomena involved; and that it is not more than ten years since any concentrated attention was given to investigate the physical phenomena, that is, the calorific phenomena accompanying the chemical phenomena, by a knowledge of which alone the natural limit to the economy of fuel can be determined. And further it is proposed to examine whether any tenable objections have been made to Mr. Bell's theory of this subject, now reproduced and perhaps rendered even more precise by Mr. Gruner in the text, §§ 4 and 5, where he defines what is, in respect of consumption of fuel, the ideally perfect working of a blast furnace.

As to the theory of the blast furnace.

In 1837-1838, Lampadius* taught his pupils that we may divide the blast furnace into four zones from above downwards, viz., into zones of calcination, reduction, smelting, and collection of products, and that therefore the charges in moving downwards must undergo the following changes. In the zone of calcination, the gaseous substances are driven off, the water, and in some part the carbonic acid of the ores

* Wilhelm August Lampadius, b. 1772, d. 1842, was chosen by the celebrated Werner, founder of the Royal School of Mines, to be Professor of Chemistry and Metallurgy at Freyberg. He introduced Lavoisier's Chemistry at Freyberg. He published his Handbuch der Allgemeinen Hüttenkunde in 1801-1810, 4 vols., and was all his life active in the publication of important works on metallurgy and chemistry.

and fluxes.

In the reducing zone, extending downwards nearly to the boshes, the desoxidation of the oxides of iron, by the carbonic oxide generated near the twyres, goes on, and the rest of the CO2 is expelled. A small portion of carburetted hydrogen also comes into play, and there is also reduction by contact with incandescent solid carbon. Towards the end of reduction the reduced iron sinters together with the substances forming the slags. The other substances present in the charges, as manganese, phosphorus, sulphuric acid, titanic acid, and such like, are only very partially desoxidized in this zone. In the zone of smelting, extending down to a point in the hearth above the twyres, the reduction of the ore is completed, and also a part of the manganese, and the acids and earths desoxidized. There are therefore formed compounds of manganese, phosphorus, sulphur, silicium, aluminium with iron, and these mix or combine with the iron, which here also takes up a certain proportion of carbon, and thus Roh eisen, cast-iron, pig-iron, fonte, is produced, a substance more fusible than malleable iron. In February, 1839, Lampadius published this statement of his views in a small work, Die Neuere Fortschritte im Gebiete der Gesammten Hüttenkunde, i. e. "Latest Progress in Metallurgical Science and Practice." That this was not the generally received theory of the process going on in the blast furnace is shown by the following abstract of a paper "On the Reduction of Iron Ores in the Blast Furnace by Hot and Cold Blast, and with Raw and Coked Fuel," published by Karsten in 1839.*

It has been asserted, says Karsten, that in cases where not

* Archiv für Mineralogie, etc., vol. xii. p. 528.