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whole of the water in it was renewed. During the whole time of the trials the pressure of the secondary steam was maintained uniformly, and this pressure preserved a certain relation to that of the steam in the boiler; on increasing the latter the pressure was increased in the evaporator and vice versa. When the steam in the heating coils was maintained at a certain pressure by means of the feed valve, the variation of the pressure of the steam in the boiler did not produce a fluctuation in that of the secondary steam, which constitutes an advantage of this evaporator as an apparatus for effecting the pulverization of naphtha. The necessary regulation is easily effected by feeding in a constant and uniform supply of fresh water.* It is to be noted that the variation of pressure in the secondary steam did not depend upon the amount of naphtha consumed; the Petrashevsky and Shtchensnovitch burners did not smoke. During the feeding in of the feed water the pressure fell 3 or 4 pounds, but upon stopping the feed pump it immediately ran up again.

On blowing out all the water the pressure fell 10 pounds; on extinguishing the burner the feed valve was closed immediately and the formation of the steam stopped at once. The regulation of the supply of steam to the burners may be controlled either by the valves on the burners themselves or else by the feed valves to the hot water heater coils. This capability increases the efficiency of this evaporator as an apparatus for effecting the pulverization of the naphtha.

The torpedo-boat rolled heavily at the time of the trials of the evaporator, but the rolling exercised no influence upon its performance; the level of the water in the gauge glass showed that the foaming did not increase. During the second day of the trial the foaming of the water in the evaporator diminished, and the projection of salt water into the burners ceased nearly altogether; on the third day this projection was hardly noticeable. It should be noted that the foaming stopped when the surface of the heater coils became covered with a layer of scale, that is, when the quantity of heat and its speed of delivery to the water were reduced. After 30 hours' trial the evaporators and the feed water heaters were opened, when it was found that the surface of

* Unfortunately the Viborg's feed pump was too large, in consequence of which it became necessary to stop it from time to time, so that the

the heater coils was perfectly clean, while the evaporator coils were covered with a layer of scale of a thickness of 1 mm. for the upper spirals, of mm. for those in the middle, the lower coils showing scarcely a perceptible amount of deposit. This deposit did not impair the evaporative efficiency of the apparatus, and the fires continued to effect a smokeless combustion and to burn the same quantity of naphtha residue as they had burned at the beginning.

The scale can be easily removed from the upper spirals by jarring them with the hand, and from the lower ones by cleaning; to effect this, the spirals are removed from the evaporator, which may be done easily and quickly. Speaking in general terms, the Krug evaporator, as an apparatus for effecting the pulverization of naphtha by steam, accomplished its purpose successfully during the whole of the experiments, and delivered to the burners a quantity of steam sufficient for the smokeless combustion of about one and one-half times the quantity of naphtha required by the torpedo-boat for running under forced draught.

Mr. Krug proposes to make certain improvements in later apparatus of this kind, such as (1) constructing the shells of the feed water heater and evaporator of steel instead of copper, as they will then stand greater pressure and, besides, will weigh less; (2) fitting both these vessels with salt water blow cocks, the need of which was felt from the beginning of the experiments; (3) introducing the feed water at the top instead of at the bottom after blowing completely through, so that the hot coils will cool throughout simultaneously and, through their change of form, will effect their own cleaning; (4) constructing the tubes of elliptical instead of circular section, so as to effect maximum deformation on contraction and expansion, etc.

Summarizing what has been stated above, the advantages that have been developed by trial for naphtha residue for fuel for ships of war are its safety as a combustible; its numerous advantages over and its superiority to coal as a fuel; the superiority of pulverization by steam over that effected mechanically or by use of air; and the accomplished development of a successful type of steam pulverizer, etc.

However, certain problems of secondary, yet of great importance remain to be solved, and experiments must be repeated

obtained. One of these questions, propounded by Captain, 2nd rank, Gavriloff is worthy of a special mention. It relates to the effect of a submarine explosion upon the walls of a reservoir entirely filled with naphtha in which the pressure of the liquid is distributed equally in all directions. Systematically conducted experiments can alone determine how disadvantageous liquid fuel would prove in such a case and to what extent this difficulty may be overcome.

Further experiments will be made during the present summer with liquid fuel in the Baltic on board the Viborg, which has been definitely assigned to the work, and upon one torpedo-boat supplied with a Yarrow boiler. On the Black Sea a torpedo-boat is being fitted out for the use of naphtha residue (formerly the Novorossisk); and trials may be made on board the torpedo cruiser Kazarski and the ironclad Rostislav.

U. S. NAVAL INSTITUTE, ANNAPOLIS, MD.

DEVELOPMENT OF ORDNANCE AND ARMOR IN THE IMMEDIATE PAST AND FUTURE.*

By P. R. ALGER, Professor of Mathematics, U. S. Navy.

The object of my paper to-day is to bring to your attention and to discuss recent developments in ordnance and armor, and to point out the direction of probable further advances. Enormous strides have been taken by both the offense and the defense in naval warfare since the days of smoothbores and wooden walls, but there is room for further progress, and although this will probably consist almost entirely in the perfecting of details, yet to the navy most successful in doing this may come the reward of a decisive superiority.

It is an axiom that the success or failure of any mechanical device, complex or simple, lies in greater or less perfection of details, and this is perhaps truer of ordnance than of anything else. The best guns and mounts are useless if the primers or sights are defective; the best projectiles are of little value if their fuses fail. Of course the prime factors for success are skill and zeal on the part of those who handle the guns, but these qualities granted, then the difference between perfection and inefficiency lies in the working out of details.

Let us commence then with the gun and consider what is being done to increase its efficiency and what more can be done. The desirable qualities in a gun are safety, power, accuracy, rapidity of fire, and cheapness. Safety and cheapness depend upon material and method of construction; power depends upon

The first of two lectures delivered before the Naval War College,

size of chamber, caliber, and length of bore; rapidity of fire depends principally upon the system of breech closure; accuracy depends, as far as the gun itself is concerned, on workmanship.

Forged steel as a material and the built-up methods of construction are now in almost universal use, and the records of proving ground and service firings show that they furnish an ample margin of safety. Wire-wound guns are coming somewhat into use, but their superiority over built-up guns, either as regards safety or cheapness, is trifling or non-existent. I suppose no experienced person doubts that an efficient, safe and cheap gun can be made of cast steel or can be forged in one piece, but the manufacture of such guns can only be defended on the score of cheapness and rapidity of production, and they cannot be regarded as in any sense equal to guns built on the present system. It would appear, therefore, that there has been no important progress made in the art of gun-building in the recent past, nor is there likely to be any in the immediate future, and I think we need have no fear of our present guns becoming obsolete before they are worn out.

The power of any gun depends on its caliber, length, and the size of its powder chamber. Taking a gun of any given caliber, we can increase its power almost indefinitely by increasing the size of its powder chamber so that it will contain more and more powder, and at the same time increasing its length of bore so that the powder may have time to burn; but this method is so expensive, both as regards weight and money cost, besides involving increased difficulties in handling and supplying ammunition, that development along its lines ceased some years ago.

Universal practice has fixed the size of the powder chamber of modern guns at a point which permits the use of a brown powder charge of about half the weight of the projectile, which itself weighs in pounds about half the cube of the caliber in inches, and the serious disadvantages which would attend any very marked departure from this practice render a radical change improbable. The plan of increasing power by lengthening the bore, however, has of late been followed to an extent which seems to me to be unwise; based, as it appears to be, on mistaken notions as to the action of the new powders, whose introduction has been followed by the manufacture of guns of sixty and even eighty-caliber

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