could have resulted would have been due to the different surface textures of these two metals, whereby the resistance of the water per unit of their surface might have been different.

These experiments show what many others have shown when properly interpreted-that the utilizations of screws of different proportions of diameter, pitch and fractions used of the pitch, and of different outlines and inclinations of the blades applied to the same vessel, vary very little unless extreme variations of dimensions are resorted to. The outline and inclination of the blades appear to be absolutely without effect upon the utilization, which is controlled entirely by the diameter, pitch and fraction used of the pitch.

The experiments show also that the method of distributing the indicated horses-power developed by the engine, originally devised and long practiced by the writer, is correct, and that by its means the important question of the resistance in pounds of the hull, per se, of a vessel at a given speed may be ascertained indirectly quite as accurately as by the direct application of a dynamometer.

The true performance and distribution of the power of the Lookout with her bottom coppered, when propelled by screw E, deduced from all the experiments, is as follows for the speed of 10 geographical miles per hour, the slip of the screw being 16 per centum of its axial velocity (product of revolutions and pitch); the number of its revolutions, 1341711 per minute; the indicated pressure on the piston of the large cylinder, 23-4175 pounds per square inch, that cylinder being supposed to be used alone; the thrust of the screw or resistance of the hull, 1631-28 pounds, as herein determined; the indicated horses-power developed by the engine, 79-5393, and the pressure required to work the engine, per se, 27164 pounds per square inch of the piston of the large cylinder alone.

DISCUSSION

Of the Papers of C. P. Sandberg on "Rail Specifications and Rail Inspection in Europe," of C. B. Dudley on the "Wearing Capacity of Steel Rails in Relation to their Chemical Composition and Physical Properties," and of A. L. Holley on "Rail Patterns," at the Philadelphia Meeting of the American Institute of Mining Engineers, held at the Franklin Institute, February 17th, 1881.

(Continued from page 36.)

66

WILLIAM METCALF, Pittsburg, Pa.: In rising to discuss Dr. Dudley's paper, I feel somewhat as I did at the Baltimore meeting— that a "crucible" man has no right to interfere in a Bessemer" discussion; yet having read the paper very carefully, I feel impelled to say something, for two reasons: First, because I believe Dr. Dudley is entirely on the right track, and having undertaken and partly accomplished a great work, he is entitled to the help of all who have experience in these matters; and second, because the data given force me to concur in Captain Jones' opinion that the analyses are incomplete, since they ignore sulphur, copper, nitrogen, and possibly other injurious elements.

In an experience of fourteen years, and with probably more than a hundred tests, we have never found the chemistry and the physics of crucible steel to disagree. If in any case a disagreement has appeared, it has been our invariable custom to go all over our physical tests with great care, and if we found no error, then to refer the matter back to the chemist, who has invariably found some unexpected element to account for the trouble.

It is only just to the chemist to say here, that ordinarily he is only expected to determine phosphorus, silicon and sulphur. Generally the metals, with the exception of manganese, are not looked for, although a watch is usually kept for copper and arsenic. Further, in most cases we have found our own work more liable to be faulty than the chemist's.

Having arrived then at such a degree of experience that we can predict the analysis from our tests, or our tests from the analysis, with almost absolute certainty, I can see no reason why the same results may not be attained in the Bessemer practice. But two things are

essential, neither of which we have here; first, complete analyses; and second, a record of the nature of the blow, the heat at which the ingots were bloomed, and the rails finished,-in short, a complete history of the manufacture.

This latter is quite as essential as accurate and complete analyses. Dr. Dudley ignores sulphur and copper on fair enough grounds commercially speaking, but when he announces so grave a conclusion as he has reached, in a scientific way, the omission of any elements that may affect the conclusion is hardly justifiable. His differences of phosphorus units, which I must term units of rottenness as far as phosphorus is concerned, and which I am sorry he did not name "Units of Alloys,"-are very small, and if sulphur and copper had been included they might have upset his conclusions altogether. The omission of nitrogen is not to be criticised in the same way, because it has not been usual to regard nitrogen in testing steels, yet I am forced to believe that nitrogen plays a very important part in Bessemer steel.

We had occasion recently to test some of the finest Bessemer steel that is made, in order to ascertain how far the Bessemer people were encroaching on the domain of the crucible steel manufacturers. In the accompanying table are the analyses of the Bessemer steel referred to, two samples of the very best foreign crucible steel, and one of the best American crucible steel.

All three of the crucible steels were of exceptionally good quality. It will be observed that, according to the analysis, the Bessemer steel should have been equally good. Upon a careful test of an 0-80 carbon billet it proved to be thoroughly worthless.

The case was then referred to Professor Langley, and he attributed the trouble to oxygen, and predicted that if we would melt a 0:40 carbon billet with a little ferromanganese to remove the oxygen and bring up the carbon to 0.80, and also give a little more silicon which the steel would take from the crucible, that we would have a steel equal to the others given above. To be sure of our work, we melted

the billet, the analysis of which is given above, and produced an ingot of about 0.80 carbon, as near as the eye could determine, and that is within 03 in such high steels. The remelted Bessemer steel was just as bad as the other, and of this we assured ourselves by the most careful and repeated tests.

Now we know oxygen was not the cause of the fault, for if it had been, the ferromanganese would have removed it. In the Bessemer manufacture immense volumes of nitrogen are blown through the molten mass, and by the evidence of all the most eminent chemists. who have examined the subject, we know that nitrogen does unite with iron, that the compound is brilliantly lustrous, hard, brittle, and even friable, and that it will harden like steel. We also know that there is a peculiar lustre in all Bessemer steel, which makes it easily distinguishable by an expert from crucible or open-hearth steel, provided none of them have been overheated. Is it not more than probable, then, that nitrogen is entitled to far more serious attention than it has yet received?

Dr. Dudley classes carbon with phosphorus, silicon, and manganese in making up his units, and he may be correct in his make-up in his relative values of each, but I cannot see how he has proved his formula, nor how it is to be disproved with our present knowledge.

While maintaining that carbon in steel is the great friend of the manufacturer and the only fit alloy of iron, I must admit that when it is present in quantity with phosphorus, silicon, manganese, or sulphur in quantity, it vitalizes and makes more active all of the bad qualities of these elements, and therefore if Dr. Dudley must have the quantities of these elements in his rails which he permits in his formula, he is quite right in saying that the softest rails ought to wear the best. In regard to the wearing of wire dies we have found

too soft, i. e., it wore too easily. Also steel of the composition

Sulphur,

0.091

Manganese,
0.387

Phosphorus,
0.02

Manganese,

0.26

Phosphorus,
0.02

and equally good and entirely satisfactory home-made steel contained

In this case good wear depends upon high carbon.

In steel rolls, in which we have had some experience, we have found that very soft rolls of about 0·30 carbon wore too fast from excessive flow, taking the shape shown in the accompanying cut, the overflow sometimes amounting to more than half an inch. This cuts away the brasses and involves much redressing. Rolls of about 0.70 carbon made from the same iron, neither flow nor crack to any serious extent, and will do two to three times as much work as the softer rolls.

Axis of Koll

We know that steel flows under pressure, that the milder the steel the easier it will flow, and the easier it will shear; yet in the paper under discussion flow is disregarded entirely, although there is plain evidence of it in many of the sections given. Low shearing stress is advised as conducive to high wear, while it would seem plain that chilled flanges must act as admirable shears to trim off "flowed" edges.

Dr. Dudley says low phosphorus units ought to give the best wear, and so they ought. He proceeds to prove it by grouping the 32 rails of least wear, and the 32 rails of most wear in two groups, and taking a mean of their analyses. By a happy accident this mean sustains his view, or perhaps it would be fairer to say, from this accident he draws his conclusions. These groups consist of all sorts of rails, of different make, different conditions of wear and different tonnages. Would it not be fairer to compare rails from the same part of the track, subjected to the same conditions of wear, of the same tonnage, and presumably of the same make? Arranging the 64 rails under consideration in this way by means of the history given, I find 30 groups, consisting of twos, threes, and fours. Comparing the phosphorus units and wear per million tons as given in the table, I find that in twelve groups the softer rails have shown the least wear, while in eighteen groups the harder rails show the least wear.

This gives 18 against Dr. Dudley to 12 for him, and it seems as if this mode of comparison were the fairer, if the presumption is correct, that the rails of these different groups were of the same make in each group, because in

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