Gill process, with gas containing as high as 75 per cent. of combustible gases, which we take cum grano salis.

What, let us now ask, is the present state of the puddling process, and what relation does its welded product sustain to the fused product of the Bessemer converter and the Siemens furnace? Will steel supplant iron?

In a paper on the Separation of Phosphorus from Pig Iron, read before the Iron and Steel Institute of Great Britain in 1878, by I. Lowthian Bell, occurs the following:

"The elimination of this metalloid from pig iron is, doubtless, a subject of great interest and importance to British smelters, having regard to the fact that nearly five-sixths of the metal obtained from their native ores contains so much of this impurity as to unfit it for the manufacture of steel, that form of iron which bids fair to supersede, in a great measure, the product of the puddling furnace."

If phosphorus cannot be removed, the question is easily settled; the production of steel is a limited one; and in the future, as at present, it will be made from the highest grades of our pig irons, and be used for certain special purposes, such as rails, etc., for which it has shown its great superiority over iron.

But, no doubt, many will at once say: phosphorus can be removed, the Thomas & Gilchrist process, with its basic lining, has overcome this difficulty. That phosphorus has been removed experimentally there can be no question; that it has been expelled successfully, from a commercial point of view, is open to doubt. Of the three processes established for its elimination, the Bell, the Krupp, and the Thomas & Gilchrist processes, the second has, from an economical standpoint, produced the best results.

There are some points in regard to all of them which, in the published results of experiments, have not been very fully touched upon, though they are of great importance. Is the increased cost of working greater than the difference in price between inferior brands of pig iron and those suitable for steel-making? This is, of course, a secondary consideration if the demand for such pig exceeds the supply, but it will be of vital importance if the reverse is the case. Is the removal of phosphorus uniform or does it vary, giving us results differing from day to day? What is the percentage of bad blooms made by these processes as compared with the usual method of working? How aniform is the quality of the final product as furnished to the con

sumer? It will, perhaps, be said that sufficient experience has not yet been obtained to answer these questions, but until they are disposed of we must be very cautious in accepting the announcement made by inventors or operators to the effect that success has been achieved. Granted that a method of dephosphorization may be established upon a commercially successful basis (and present indications seem to point to such a conclusion), what will be the resulting product, and how well will it be fitted for its intended uses?

In advocating the use of high qualities of steel, and enumerating the advantages to be gained by employing it, the fact is frequently: lost sight of that this superior metal is made from the highest grades of pig, obtained with the greatest care from the purest ores, and that the succeeding processes are worked out with the aid of the most improved plant. The metal is followed through all details of manipulation with the most thorough inspection and rigid chemical and. mechanical tests. Material thus obtained is compared with wrought iron made from anything and everything. No chemist mixes thecharge or analyzes the product, but a puddler is left to guard the interests at the most vital stage of the process. It is his aim to produce the greatest weight, with the least labor, in as short a time as. possible, and with such work no one can blame him. It is not astonishing that under such conditions iron is so much inferior in its physical qualities to steel. Even taking the same grade of pig metal for the manufacture of wrought iron as is now used for steel, the mild. grades of the latter suitable for structural purposes will, no doubt,, give higher results by mechanical tests, but the difference between the two will not be as great as many are apt to think.

On the other hand, if in the future, by means of dephosphorizing: processes, we shall use all sorts of pig iron for steel, shall we not introduce a dangerous element of uncertainty into its manufacture: which we do not have to deal with at present? When it is considered. how very slight a change in the percentage of some foreign substancemay produce a considerable variation in the quality of steel, uniformity in a metal derived from such impure raw materials must be difficult to attain. The homogeneous nature of steel, as compared. with the many-pieced structure of iron, is claimed as one of its advantages. Homogeneity in steel may be a cause of weakness, and the lack of homogeneity in iron a source of strength. A steel bloom, to all external appearance perfect, may be within entirely bad, either

from piping in the moulds, or from other causes of a similar nature. Chemical analysis will not show this defect, and a bar produced from the same, although sound as far as can be seen, may fail in service suddenly and without warning. On the other hand, the possibility of a wholly bad iron bar diminishes just in proportion as the number of pieces in the pile from which it is made increases.

For a material for structural purposes the term uniformity should take the place of homogeneity. A material exposed to abrasion, such as a rail receives, requires the latter quality, but one subjected to strains of compression and extension, tension and bending, wants uniformity more than any other property. If one bad member is contained in a structure the strength and homogeneity of the whole is of no avail. For many purposes in construction steel may be used to very good advantage, notably for members liable to wear and parts running in bearings. But whenever it is applied in parts of varying outline, where sudden changes in form take place, planes of weakness are developed at all those points at which anything like a corner occurs, unless large fillets are used and great care is taken. It must not be forgotten that the structures hitherto erected of steel, have been, as it were, experimental, and have therefore been put up with the closest inspection, and caution. If it should be generally adopted, this same care could not be exercised unless an entire revolution in existing modes of manufacture takes place. The rough handling which iron for structural use receives in manipulation would be fatal to steel. Existing plant and methods of working must be abolished, and workmen be educated in the proper handling of the new products.

Looking upon the above objections as a few of the more important ones yet to be met before a more general use of steel can take place, it will be apparent that its substitution for wrought iron will be very slow and gradual. The puddler and his furnace yet have many years before them. No one could regret it more than the writer. No other process in iron metallurgy requires so much work per ton of metal produced. It seems absurd to think that the labor of two men for ten hours is necessary tr produce a ton of wrought iron, and that for one ton of pig iron used one ton of coal is consumed! It is not worth while to consider those methods which aim merely to lighten but do not do away with the labor of the puddler. They may have some advantages, but they will never come into general use. What is needed is a method which is governed by intelligence, but which requires only

ordinary labor for its working. The rotary furnace process is the only one which at present aims at this result, but its complete success is open to doubt. The wear and tear of the complicated mechanism and revolving surfaces is a source of expense, and the lining is composed of a material not well calculated to resist heat. The quality of the iron, however, is good, and counterbalances many of the attending disadvantages, although it will not, as was at one time hoped, answer for making bars without weld. It must be cut and piled as ordinary iron, or the work upon it will not suffice for good results.

We are now in the midst of an epoch of uncertainty; a few years more and the success or failure of steel to supplant wrought iron will be established beyond a doubt. Its success depends upon the results which shall be obtained from the working of all grades of pig iron; and its failure is certain if uniform quality cannot be produced. For the present, therefore, the system of puddling must continue as of old; but every ironmaster, not only of this but of other countries, will most gladly welcome the process, whether it be of steel or of iron, which shall do away with the weary toil of so many thousands, and usher in a brighter and a better era than could ever be accomplished by the puddling process as invented by Henry Cort.

Relation of Spectral Rays to the Constitution of Nebulæ. -Ch. Fievey has made the spectral rays of hydrogen and of nitrogen the subject of a special careful investigation. By attaching to the spectroscope a contrivance which enables him to regulate at will the quantity of light received, he observed that the spectrum of hydrogen was modified and simplified in proportion as the brilliancy diminished. The H line first disappeared, then C, and finally only F was left. It is well to remember that the F line is the only one of the hydrogen lines which has been observed, in a large number of nebula that have been examined by the spectroscope. The spectrum of nitrogen gave results similar to that of hydrogen. It is, therefore, not strange that we should meet, in nebulous spectra, only the rays which are most persistent in diminished light. Such rays may suffice to establish the presence of the body to which they belong, and the disappearance of the others may be explained by their extinction in traversing the intervening spaces.-Bull. de l'Acad. Belg. C.

SLAG CEMENT.

We have on several occasions directed attention in this Journal to the very important question of the satisfactory utilization of the slag produced from blast furnaces. In past years this product has been accumulating to a vast extent, and the ironmasters have been put to enormous expense and inconvenience in providing places of deposit for many millions of tons of this, until very recent date, comparatively useless article. It is true that in some few instances it has been employed in filling up shallow bays, and even for making roads in the immediate vicinity of the works where it is produced, and where other more suitable material cannot be conveniently supplied, but for both these purposes the demand has been extremely limited, and in the vast majority of cases it has been got rid of as so much rubbish.

One very important use to which blast furnace slag has been proposed to be put has been in the production of bricks for building purposes, and for this application Mr. Charles Wood, the manager of the Tees Iron Works, Middlesbrough, obtained a patent in the year 1873, and full description of the processes employed by Mr. Wood have -appeared in our columns. More recently we had occasion to speak of a patent obtained by Mr. Frederick Ransome (who for nearly forty years past has been prominently before the scientific world as the inventor of several ingenious and valuable processes for the manufacture of artificial stone) for the production of an eminently hydraulic cement, in which the slag sand from the blast furnaces forms a conspicuous and very important feature, and of this cement we have now something more to say. Good Portland cement, which now enters so largely into the construction of all hydraulic and substantial building operations, is, as our readers are aware, a compound of silicate of lime and alumina, and contains about :