to.. Conditions that are regarded as likely to be dangerous are immediately reported and steps taken to correct them.

The procedure in obtaining a permit for a magazine is as follows: The contractor makes application to the Inspector of Combustibles, Fire Department, for a magazine of the desired class and forwards this to the Division Engineer, who sends it to the Chief Engineer of the Commission. The Chief Engineer forwards it to the Division of Combustibles of the Fire Department with his statement whether the work in the vicinity requires the use of explosives and whether the amount asked for is a reasonable one for the needs of the contractor. permit is issued by the Fire Commissioner until this statement of the Chief Engineer or his representative is received.

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I have always felt more concerned about the conditions during the cold weather, when with the old form of explosives it was necessary to thaw the cartridges before they could be used. With the new form of explosive, which freezes only at low temperatures, this danger is to a large extent avoided, and we feel somewhat easier in consequence. On the subway work these low freezing compounds are generally used. 40 per cent gelatine is used for the open cuts and 40 to 60 per cent for the tunnels.

Mr. MacIsaac has spoken of the methods used in loading the heading holes, and has pointed out the advantages, from his point of view, of loading all the holes in the face before any firing is done. While I do not like to differ from so excellent an authority as Mr. MacIsaac, whose practical experience in such work lends weight to anything he may say on the subject, I am still inclined to believe that the safer method is the one which was favored by the engineers on the Catskill Aqueduct, that is, loading only the round to be fired.

I heartily agree with Mr. MacIsaac's opinion of Section 188 of the regulations of the Municipal Explosives Commission, and believe it is far less dangerous to withdraw the charge from a missed hole than to attempt to drill a new hole parallel with the old one. The risk of the drill striking the old charge and exploding it is greater, I believe, than the risk of withdrawing the old charge, if this is carefully done. Of course, only careful and competent men should be employed to draw the charge.

JOHN R. HEALY.-Mr. President and Gentlemen: I think

hat the Brooklyn Engineers' Club is particularly fortunate this evening in having heard Mr. MacIsaac, General Manager of the firm of Grant, Smith Co., Hauser and Locker. Mr. MacIsaac was in direct charge of Contract 66, and his practical experience in the use of explosives was a source of assistance much appreciated by the engineers of the Board of Water Supply.

As to Mr. McIsaac's views on the matter of separate loading of headings, I disagree with him as do practically all the engineers who have had to do with such matters. Mr. MacIsaac expressed the opinion that the dynamite inspectors of the Board of Water Supply could have done more effective work if they had greater powers and could have revoked the licenses of the heading foremen and blasters when they were found violating any of the rules of the Explosives Commission. I do not agree with Mr. MacIsaac in this. Dynamite inspectors had ample authority and the same results were obtained under the existing conditions because of the fact that all the contractor's men knew that they were expected to live up to the regulations and observe every measure tending to additional safety, and they fully realized that if they were found violating any of these requirements something was bound to happen to them.

I agree with Mr. MacIsaac, as I believe do most of our engineers, in the opinion he expressed as to the handling of unexploded holes. I have never seen a drilling crew cut a hole twelve inches from a loaded one, probably because I would not remain in the heading to see them do any such trick. I have, however, seen the dynamite and exploders removed from a number of holes by means of compressed air. This is a dangerous proceeding unless the manipulation is done by an experienced and careful man. If a heavy pressure of air is blown into the hole fragments of stone may be blown against the dynamite with sufficient force to explode it. If the pressure is turned on lightly, and the nozzle of the air hose, having been inserted in the hole, is turned on slightly, the sticks of powder will follow after it just as a rod of iron would follow a magnet.

I would like to say a word or two about the work done by the so-called dynamite inspectors. I believe that their work was successful, but I do not believe the services and the difficulties of their jobs were fully appreciated even by the engi

neers associated with them in the work. These men had to know what powder was stored on the job at all times, how it was handled and how it was used; they were required to be present while the powder was being placed in the holes, and had to go back into the heading with the firing squad after the shots had been fired to see enough of the conditions to satisfy themselves that the loading of the remaining shots was done in a safe manner.

A humorous incident connected with the handling of explosives involved a new employee of the Board, who was assigned to inspect dynamite. His superior decided to try him out by taking him into the smoky heading during the shooting, and after they had been in the thick smoke from thirty to forty minutes the engineer, green with nausea, decided that he had enough and would go on top. The new man, however, said that he would like to stay down and see the shooting finished. The superior could not very well object, and went to the surface wondering what sort of man this fellow could be. It was not until sometime afterwards, that he learned that the supposed neophyte was a retired fire lieutenant who had been "eating smoke" for years.

JAMES F. SANBORN, Mem. B. E. C.-Commenting on Mr. MacIsaac's remarks regarding the advisability of separate or combined loading of the holes in the tunnel headings, I wish to call attention to what was perhaps the most serious single accident due to an explosion in a tunnel on the Board's work. This occurred at Cold Spring, N. Y., in January, 1911. Ten men were killed in this accident. At the time, the tunnel was in very tight rock, so that it was frequently necessary to shoot the cut three times to break it to the bottom. On the day of the accident the cut had been shot twice, and fifteen men of the gang had gone back to assist in the operation of reloading the cut for the third time, and to load the side rounds. Ten minutes after the gang had gone in an explosion killed ten of the gang and injured the other five

From an inspection made by Mr. Ridgway and myself, we are convinced that the explosion was due to some cause affecting the dynamite in the boxes from which the men were loading the heading. It is certain that none of the holes in the heading went off.

While it is impossible to draw conclusions from any single case regarding the advisability of separate or combined loading, it seems to me evident that in this case the accident would not have occurred if the entire heading had been loaded before shooting the cut. It is probable that the presence of powder smoke from the previous shooting and the rather bad lights used were more or less directly responsible for this accident.

No. 125

GAS ENGINES AS PRIME MOVERS FOR POWER AND ELECTRIC STATIONS, AND THEIR APPLICATION

TO THE MODERN GAS PUMPING STATION.

BY L. S. STILES, MEM. B. E. C.

PRESENTED MAY 14, 1914

A fitting introduction to the paper to be presented is given by a general description of the 10-million cubic-foot gas holder of The Newtown Gas Company, located in the Borough of Queens, on North Hempstead turnpike about 1⁄2 mile from the Hoffman boulevard. This holder, the largest steel tank holder in the world at the time of its completion in 1910, made necessary the erection of the gas pumping station, which forms the subject of this paper.

TEN-MILLION CUBIC-FOOT NEWTOWN GAS HOLDER

A gas holder of 10-million cubic-foot capacity has a tank diameter of about 251 feet and requires a plot of ground about 258 feet square, not including the space required for auxiliary apparatus, as for instance a boiler plant and coal storage for the purpose of heating the tank and holder cups in the winter time to prevent freezing, or a gas pumping station to be erected in conjunction with the holder. The average city block is 200 feet wide, and it is evident that the quest for a suitable location of a holder of this size is not very simple.

But aside from the large area required, there are other important conditions which must be fulfilled before a definite choice of location can be made.

The ground should be at a low elevation in order that the holder which reaches about 275 feet in height when fully inflated may be made as little objectionable to the eyesight as possible, and again, in order that the pressure may be maintained. It is well known that the pressure of gas increases one inch water column for every 200 feet of hight, or in other words, if the gas holder were placed high and supplied a low lying district, a pressure equal to one inch water column would be lost for each 200 feet that the supplied district is below the holder. Whereas