JACOB REESE, Pittsburgh, Pa.: I have been very much interested in the reading and discussion of Dr. Dudley's paper. As far as it relates to the data of work performed by the rails, and the determination of their physical and chemical properties, I have nothing but commendation of Dr. Dudley to express, as the investigation covered a greater range, and was performed with more care in detail, than any similar work which has come under my notice. But I beg leave to differ with Dr. Dudley in his conclusions.

What are the factors of hardness? Are they not carbon, silicon, phosphorus, and manganese? Now it is an undisputed fact among metallurgical experts that pure carbon and pure iron make the best steel of all degrees of carburization, and for all purposes. While carbon hardens, it also strengthens the metal, but silicon, phosphorus, and manganese, in hardening, make the metal also brittle, and are injurious any amount. Carbon should be called a strengthener; and I claim that a steel rail made hard with carbon, with the other three hardeners absent or reduced to a minimum, will carry a greater tonnage than any of Dr. Dudley's soft rails.

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But until the basic process is put into operation in this country we cannot expect to produce Bessemer or open-hearth steel without the presence of silicon, phosphorus and manganese, in considerable quantities, and I greatly doubt the possibility of reducing the percentage of any of them by the present practice without seriously diminishing the output, and correspondingly increasing the net cost of production; which is an important question, since the increased life of the rail may be more than balanced by its increased cost.

I think that the soft rails performed a greater amount of work, because they contained a less amount of silicon, phosphorus and manganese (brittlers, if I may so term them), and that carbon does not reduce the wearing capacity of rails. I believe that a rail made by the basic process, with silicon, phosphorus and manganese reduced to a minimum, and containing 0-60 carbon, will be stronger and tougher, and will carry double the tonnage of any of Dr. Dudley's soft rails. (To be continued.)

Pronunciation of Foreign Languages. The Polyglot institute at Paris proposes to try a phonograph of new construction, in order to teach its pupils how to pronounce correctly the difficult words of foreign languages.-Chron. Indust.

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BOILER EXPLOSION AT GAFFNEY & CO.'S DYE WORKS, PHILADELPHIA, JUNE 1, 1881.

By W. BARNET LE VAN.

A cast iron flat boiler head only two inches thick would not be considered by an experienced engineer strong enough for a cylinder boiler thirty-six inches in diameter, especially when the rim by which it was secured to the shell plate was only 1.625 (1) inches thick, with scarcely any fillet at its junction, and this rim being placed so as to project into the shell of the boiler, when it should have projected outside, according to the usual practice.

The insufficiency of such a boiler head was proved, with fatal results, on the 1st of this month, at the dye works of the above-named firm. The head of this boiler blew out, killing three persons and wounding eight, besides damaging property to the amount of about $15,000.

The boiler, which was new, was built by Messrs. Sidebottom & Powell, of Frankford, Philadelphia, for Gaffney & Co., and was inspected by a Steam Boiler Insurance and Inspection Company on the 2d day of March, 1881, and tested in connection with two similar ones on the 7th of the same month, by hydraulic pressure of ninetyfive pounds per square inch, and was passed by this Insurance and Inspection Company as capable of carrying a working steam pressure of sixty-five pounds per square inch above the atmosphere.

During the examination of this company's inspector, before the Coroner's Jury, he stated, in answer to a question from one of the jurymen, that "there were quite a number of boilers in this city which had cast iron heads, and that his experience had taught him that a concave cylinder boiler head was stronger than a flat head." Yet he passed this flat cast iron head without any comment at the time to the attendant owners or the insurance company in whose charge it was placed.

This disc of cast iron (the boiler head) took its full load of about 30 tons without any other support than that at tue connection of the rim with the shell of the boiler.

The cylinder head of a sixteen inch diameter engine would have

been made one inch thick, and yet this boiler head, having twenty times the area, upon which the pressure was exerted through a threefold greater leverage, was but twice as thick. A thirty-six inch engine cylinder head would have been cast hollow concave, or else stoutly ribbed on its face; yet this boiler head was a plain flat disc, only two inches thick, and the rim, which is at right angles to the head, only 1.625 (13) inches thick, with scarcely any fillet at its junction, and this rim being placed inside of the boiler the steam pressure acted on it by tension, in place of by compression, at its weakest point. Had the pressure acted by compression on the rim of the head, it would have resisted nearly twenty per cent. more pressure before parting. An examination of this head after the explosion shows that it was under internal strains resulting from bad design as to form and proportion.

It is a well-known fact in mechanics that, in casting plates of iron, if one part is less in thickness than the larger portion of the casting, especially when two surfaces join each other at right angles, as was the case with this boiler head, the difference in cooling will cause internal strains, in some cases to such an extent that when a casting becomes cool it may break by the unequal contraction of the several parts, without any pressure whatever. The effects of these strains to reduce the ultimate strength of the boiler should be taken into account as an important element, as in this case a part of the factor of safety was already expended, by reason of the improper construction of the boiler head in this respect.

Another great defect in this boiler head was that the man-hole plate was not properly fitted to its seat on the head; the seat was a planed surface, and the man-hole plate was a wrought casting, so that in making a steam-tight joint between the two a strain was induced additional to that due to the improper design and proportions of the head, as before explained. Had this boiler head been made concave, and of an average thickness of 1·25 (14) inches, with the convex side inward, with a round man-hole in place of an oval one, and thickened around the same on both sides, I have no doubt whatever it would never have given away; but, better still, it should have been made of wrought iron, dished, and with the convex side projecting from the boiler.

Now that a board of engineers is about to revise the boiler inspection laws of this city, would it not be well to add a clause providing that cast iron should be dispensed with altogether in the construction

of steam boilers, unless so employed as to conform with well-known and approved design and proportions, and so placed in the boiler as to resist the greatest amount of steam pressure with the least amount of metal?

The writer does not hold cast iron to be an improper material, but from the fact that its proper form for resisting heavy pressures is not understood by the majority of our boiler makers, and even with the most skillful moulders a perfectly homogeneous casting is the exception and not the rule. The thinner a casting is made the more homogeneous it will be, all things being equal. Assuming the form and design to be unexceptionable, the use of cast iron is attended with greater risk than that of wrought iron, and should be regulated by such judicious proceedings as will tend, as far as possible, to render its employment (which is often convenient and desirable) sufficiently safe to be unobjectionable upon the grounds above referred to. Philadelphia, June 8th, 1881.

AUCHINCLOSS' AVERAGING MACHINE.

The Averaging Machine (or Book-keeper's Assistant) gives mechanical expression to an important branch of mathematical science, and employs manual instead of brain work in the process of determining the average date on which payment falls due.

It seems odd to think of so imponderable an element as an average date being determined by material objects, such as leaden bails, or bits of metal, and being weighed out like articles of merchandise. This, however is not only practicable, but the apparatus will determine with unfailing accuracy the average dates of more than one hundred accounts per hour. It requires no skilled mathematician for its manipulation, as the same results can be secured by those who know little about the use of figures.

The machine is exceedingly simple. It consists of a grooved platform, balanced by a scale beam and pan. The pan is so coupled with a moving counterweight that the equilibrium of the system is preserved for all positions of the pan. The weights bear to each other the ratios of 1 to 10 and of 1 to 100, so that they may be used to represent units, tens, hundreds; tens, hundreds, thousands; hundreds, thousands, tens of thousands, and so on.

problem, the weights are first distributed over the platform so as to represent the several purchases made on the respective days. The scale pan is then laden with an amount exactly equal in weight to the entire load upon the platform. After the machine has been thus

The grooves of the platform represent the days of the month, and the notches on the scale beam the average dates. In solving any