usual form of lap-welded joint. The welds were not always perfect, as is probably the fact with all such pipe; but this pipe, buttwelded, would have borne very much higher pressures than those to which it was subjected in ordinary work, by the steam carried on the line. It cannot be asserted that these lengths of pipe did not split under pressures less than those to which they were afterward subjected in the tests, as it is very possible that the first blow may have found a weak part of the pipe, and the split may, in some cases, have extended to a stronger portions. Nevertheless, the writer is inclined to believe that this was not the case in all instances, and is convinced that, in one case at least--that of the 8-inch crack, which was accompanied by a decided bulge in the pipe-the water pressures, at the test, were, at least approximately, equal to, and are very likely to have exceeded, those obtained at the later test. It seems very certain that we may consider it as proven that the pressures produced by "water-hammer" are often enormously in excess of those familiar to us in the use of steam, and that they have, in many cases, exceeded 1,000 pounds per square inch. It is, then, evident that it is not often safe to calculate upon meeting these tremendous stresses by weight and thickness of metal, but that the engineer must rely principally, if not solely, upon complete and certain drainage of the pipe at all times as the only means of safely handling steam in long pipes, such, especially, as are now coming into use in the heating of cities by steam led through the streets in underground mains.

The facts here presented have been, to the writer, something of a revelation, and have seemed to possess unusual interest and importance to the engineer using steam under such conditions as are here referred to. It is a fact which has long been well known, that these suddenly produced pressures are often very great. The write has occasionally, for many years, known of serious and sometimes fatal, accidents due to this cause; but that these stresses are often as great as is here indicated has probably been little realized by engineers generally.

DISCUSSION.

Mr. Chas. E. Emery.-Last fall the New York papers were filled with accounts of explosions of steam pipes, and in spite of all protests they refused, except in their advertising columns, to call attention to the fact that there were two steam companies in that city, and that the difficulties complained of were on the lines of but one of them.

WATER-HAMMER

Few read the advertisements, and the press outside of New York copied only the news items; so to this day there is a general impression all over the country that steam enterprise in New York has been a failure. While, ordinarily, engineering facts are valuable, without reference to time, place or persons, the above statement, with some explanations farther on, show the necessity in this case of stating at the outset that the New York Steam Company has been supplying steam continuously since April of the year 1882, while another company, viz., the American Heating and Power Company, upon whose plant, as is well known, Professor Thurston reported, actually ceased operations early in the winter of 1882-83, after a few months' abortive trial, and is now in the hands of a receiver, who is endeavoring to sell the property in the interest of the bondholders.

The phenomena of the water-hammer is familiar to most steam engineers, particularly those who have had to do with the large pipes used on ocean steamers. The writer, from his connection with the New York Steam Company, had full opportunity to observe the operations of the American Company, and is surprised to find in the paper under discussion no reference to what he considers one of the chief causes of the difficulty experienced in operating the pipes of that company.

It was actually and persistently attempted to carry superheated steam in their underground pipes. The regular superheaters provided were never used, but a series of pipes in the boiler settings answered the purpose to a certain degree, superheating the steam, it was said, some 60° or 70°-probably more at times, as the demand for steam varied; for who could regulate such an apparatus, or, in fact, in regular practice, any apparatus for such a purpose? The results are evident on consideration. The branches of the line where little or no steam was used soon cooled down, so as to contain only saturated steam, and at times all the branches were in this condition. Upon opening a valve anywhere, however, a circulation would be established, which slowly but surely would bring the superheated steam into that line, and all the conditions to produce unusual strains or cause even an explosion, would be present as soon as the steam reached any collection of water; for the reason that water, which is harmless in the presence of saturated steam of the same temperature, would act as an efficient refrigerator of steam at a higher temperature, though of the same pressure as that due to the temperature of the water.

WATER-HAMMER

The reduction of volume thus caused would not be as great as if steam were brought in contact with cold water, but entirely sufficient to cause a flow of steam from both-and at junctions from several directions, some of the currents perhaps bringing more water to reduce the volume of more steam, thereby causing collision with a necessary great increase of local pressure, straining the pipes, causing the joints to leak at all sorts of odd places where there were apparently no reasons for the difficulties. The more violent explosions were undoubtedly due to a combination of the straining effects due to the reduction of volume of superheated steam, with the more potent one of direct contact of steam with water cooled during times of inaction; below the temperature due to the pressure, the forces being brought in action more strongly when the steam was conducted through one pipe to heat an adjoining one.

The conditions which brought about the bursting of the pipes undoubtedly varied with the circumstances of each particular case, and with the peculiarities of each location. Extreme business pressure prevents the writer from fully discussing the subject at this time, and its farther consideration must be left for a proposed paper on the general subject of "District Steam Systems," which it is expected will be prepared when all the problems necessary to a complete mechanical and financial success shall have been analyzed and the necessary apparatus put in practical operation.

NOTES ON STEEL.

BY

GUS. C. HENNING, M.E., PITTSBURGH, PA.

THE use of steel as a material of construction is becoming so general, that it is no longer a question whether we can obtain a material which can be relied upon, but merely when steel is used whether the sections of individual members will not become too light, when of the same strength as designs in iron, so that the structure will be destroyed by corrosion or minor accidents, rather than by use, unless unnecessary weight is added.

It is a well known fact that the sole reason why perfectly homogeneous Bessemer steel is not made in this country, is this: that there is a greater profit in steel for rails, with less work, than there is in steel for structural purposes, in addition to the fact that rails can be made in stock, but shapes cannot very profitably.

It is but quite recently that any attempt has been made to obtain a perfectly reliable and uniform material on a large scale, and then generally by using Siemens or Pernot furnaces.

In England, France, Belgium and Germany, the state of structural steel manufacture is far advanced, and for the simple reason that engineers in those countries insist upon a uniform material, and the quality of the output of any works determines its commercial success and progress, rather than location or political or personal influence. In this country the larger structures designed of steel are few in number, and the following table is a complete list to date.

The steel for these structures, as far as completed, was quite uniform in chemical analysis, as well as in mechanical properties, and

in every way superior to and more satisfactory than any grade of bridge iron from any mill.

Imperfect welds are not to be feared, as welding was in no case permitted; any hard spots could be easily removed by careful and thorough annealing.

It is true that some of this material was abused during fabrication, from waut of knowledge of and experience in the use of steel, but this could have been prevented by proper procedure; where proper care was bestowed upon the work there remains no doubt about the superiority of the structure.

The quality or uniformity of the material used in any structure depends mainly upon the kind of inspection it receives at the steel works, while the quality of the structure depends upon the experience and care of the inspecting engineer at the bridge shops; if the former performs his duty faithfully and accepts only such material as is fully up to the specification requirements, and the latter watches closely every process during fabrication and prevents all abuse, there is but little doubt that a superior structure will be obtained. This, of course, requires experienced inspectors, whose judgment must be correct and based upon fact, and who, at the same time must be on duty at the bridge shops at all hours with the men.

Below is given a table, containing a number of tests of eye-bars which were recently made at the Keystone Bridge Works, and the results of which are equal, if not superior, to anything that has been done heretofore.

The tests as given in Table No. 1 were made upon bars fabricated by the following method:

The bars were at first heated in the neck, while the end was protected from the heat by a covering of refractory material; upon reaching a bright red heat, the bar was placed in the hydraulic upsetting machine and partly upset. Whenever this upset showed any wrinkles or uneven edges, these were drawn down under a helve hammer and fullered out. Then the bar was returned to the furnace and heated nearer the end, and again upset and worked under the helve hammer. Three heats complete such an upset, when the bar is again heated to a bright red and the eye is shaped in the hammer die, from which the bar is taken to another helve hammer, under which it is drawn down to the required thickness and given the correct set. This sometimes requires another heat before the end is finished, when the eye at the other end of the bar is made in the same manner.