sight, or to the level; but, for short or medium ranges, the cam would be used exclusively, with the certainty of thus obtaining, with all necessary accuracy, a rapidity of fire which cannot be claimed for any other method whatsoever. The new process appears then to be what would best suit the defense of comparatively narrow passes, because, in this case, rapidity of fire becomes a matter of imperative necessity. APPENDIX. Graphic Method. -The memorandum dated from Brest, December 12, 1892, contained no indication as to the construction of the eccentric. Since that time we have, thanks to the courtesy of the director of artillery, been able to procure, at that port, tables of fire, which have permitted us to fill that hiatus. The given elements of the problem are the angles of elevation supplied by these tables, and the elevation of the battery above the level of the sea. Let us take for example the Horse Shoe Battery at Brest, of which the altitude H is 27 meters, and let us seek the profile to give the cam, for the 32 c. guns constituting its armament, assuming for A, the distance of the rear sight from the front sight, a length of 11⁄2 meters. First prepare a table containing in column 1, a scale of ranges 200 meters apart; in column 2, the angles of depression i corresponding to these ranges; in column 3, the trigonometric tangents of these depressions; in column 4, the angles of fire given by the tables; in column 5, the differences between these angles and the corresponding depressions i of column 2, in other words the values previously termed a. m/m 139 21 67 65 Column 2. The depressions are calculated by the formula =27 meters). In order that the eccentric or cam may properly express the relation sought between i column 2 and a column 5 it is necessary that: +250 + 315 1. The tangents of the angles (i) of depression shall be represented by the variations of the different radii of the eccentrics. 2. The values of a shall be represented by the angles separating these various radii. To this end, we establish first the maximum and minimum ranges for the cam. For the latter, we will not go lower than 250 meters, otherwise the curve of the eccentric would be too pronounced to insure the motion of the front sight rod satisfactorily. (To fire on a target at a less distance, recourse would be had to the natural line of sight for elevation). As to the maximum distance, variable with the altitude it would be best to decide it once for all experimentally. Let us suppose it to be 4000 meters for the battery in question. To aim between these two distance limits, 250 and 4000 meters, the cam ought to make a complete turn upon itself, or 360, while the angular dis placement of the breech varying, according to our table, from -7° 40′ to → 6 16', will reach at most about 15 degrees Besides, the rotations of the breech and of the eccentric, both depending on those of the elevation cranks, are proportional. vary. Let be the constant relation according to which these two displacements This constant relation is arbitrary; but it is for our interest, in order to diminish the curvature of the eccentric, to make it as large as possible; 360 thus, in our example, we adopt k 15 24. We have now all the necessary elements for the design of the cam. It will suffice to carry out the following operations indicated by figure 6. Describe a circle with any convenient radius. Take the radius om.40, for example. From the center lay off a number of radii making with one chosen as an origin angles respectively equal to the products of ka, this is represented by 740 X 24, 3028' X 24, etc. These angles are laid off to the left of the origin if negative; to the right, if positive. Upon each of the radii thus drawn, and starting at the circumference, lay off, towards the center, distances equal to the variations 4p of the radius of the eccentric; these variations as we have said, are nothing more than the tangents of the depression (i), that is to say they are equal to the trigonometric tangents of column 3 of the table multiplied by the distance λ = 1.50 meters. We thus obtain as many points as there are radii and their number is, besides, indefinite. Join these points by a continuous line which will represent the profile of the cam. §1.-In conclusion, notice that the angles of column 4 taken from the tables of fire, are absolutely true only for a horizontal line of sight. In retaining them thus we have therefore admitted implicitly the principle of the rigidity of the trajectory. This hypothesis not being applicable to the case of elevated batteries firing at short range, it will only be necessary to make in the angles of column 4, and hence in those of column 5, a small correction, well known in artillery, to obtain the outline of the eccentric with the utmost exactness. Profile of the cam for a 32 cm. gun. Horse Shoe Battery. Reduced Scale. In order to diminish as much as possible the curvature of the eccentrics and to prevent the front sight guide rod from binding, it is our interest, as we have moreover done, to give to k and to p their maximum value. To determine p, the radius of the eccentric, we are absolutely limited only by the consideration of bulk. We can, besides, diminish the volume of the cam very much by dividing the play 4p of the front sight G, between it and the rear sight, allotting one half to each. In this case the rear sight would also become movable and be supplied with an analogous cam. §2.-The very principle of the snail shaped cam supposes the masonry platform of the gun to be perfectly horizontal. Practically this is not at all the case, and the traverse circle upon which the carriage rolls may be several minutes out. In this case, if the distance from the target is considerable, a little correction becomes necessary; to effect this, the rear sight A, instead of being Journal 53. rigidly fixed to the top carriage has a slight vertical movement. This displacement is regulated by the readings of a little level set in the chassis, This level reading and change is done by another gunner without requiring the man at the sight to stop his sighting. When the object is within short or medium distances, the error in aim, arising from this defect in the platform may be neglected and there is no necessity for taking the trouble to make the correction for it. Naiade, August 27, 1893, H. DE KERILLIS, Lieutenant. [Translated by Captain G. G. Greenough, Fourth Artillery, U. S. Army.] WAR SHIPS AND TORPEDO BOATS. Merchant Steamers as Navy Vessels. On the 21st of October the fast steamer Normannia of the Hamburg-American Line under the command of a navy captain was placed in service at Kiel for fifteen days. With this steamer the attempt was made for the first time in the German Navy to determine to what extent such reserve ships can replace cruisers and despatch boats. The special conditions of construction which the Navy Department imposed on the Hamburg-American and the North German Lloyd lines, in return for a subsidy granted them, and according to the terms of a special war contract, which guarantees indemnity against loss, are in the main as follows: The body of the ship to be made with double walls and protected by a system of compartments reaching up above the water level; for the purpose of cominunication doors to be retained, but to be such as can be closed water tight. Machinery and boilers are protected by coal bunkers; the coal in these is a reserve fuel, and can only be used in extreme necessity. In a ship of the size of the Normannia (8520 tons gross capacity) the ordinary coal bunkers hold 1750 tons. The ammunition maga zines lie protected in the ship's hold, and are so arranged (as is the case in naval vessels) that they can be put under water. For the armament there are carriages for four 2.5 cm. (4.92 inch) guns, L/30, two of which stand in the bow and two in the stern, for fore and aft firing, also others for eight 15 cm. (5.9 inch) guns, L/25, in a broadside, for two 9 cm. (3.5 inch) guns, for two 56 mm. (2.2 inch) quick-fire guns, for six 37 mm. (1.5 inch) rapid-fire guns and for eight mitrailleuses. In the way of ammunition there are 150 rounds sup. plied for each gun of medium caliber, 200 for each gun of small caliber, and 1000 for each quick-fire gun. In addition, the steamer carries two small torpedo boats of 22 tons displacement each, with special arrangements for lowering and raising. For each torpedo boat eight torpedoes are provided. Such an auxiliary steamer would rate at least as high as the third class cruiser Gefion. The question of manning these auxiliary cruisers would present no difficulties, since in our country with universal service the larger part of the men on every steamer have served in the navy. This is as true of the engineers as of the sailors, and it would be merely necessary in time of war to put on board, besides the staff, several petty officers and a few sailors of the navy. -Mittheilungen aus dem Gebiete des Seewesens, No. XII, 1895. BOOK NOTICES. Johnson's Universal Cyclopedia. A new edition prepared by a corps of thirysix editors, under the direction of Charles Kendall Adams, L.L.D. President of the University of Wisconsin. D. Appleton & Co. New York. 1893-1895. $6.00 per volume. Encyclopædias, we are told by one who made great use of them, are books "where one may learn without cost of research what things are generally known. For it is far more useful to know these than to know those that are not generally known". (Lowell, Books and Libraries). The work before us is now complete in eight volumes, containing each over nine hundred pages in which are treated from five to six thousand subjects, and in the selection of the subjects and the character of the articles it conforms in a remarkable degree to Lowell's idea of what a cyclopædia should contain. The editor-in-chief as well as his corps of assistants are each and all men prominent in the departments which they have undertaken to direct. The managing editor, Robert Lilley, had previously had the invaluable experience of being one of the editors of the Century Dictionary. Among the associate editors we find such names as Dr. William T. Harris, United States Commissioner of education, Professor Theodore S. Woolsey of Yale University, Professor Ira Remsen of Johns Hopkins University, Simon Newcomb, Editor of the United States Nautical Almanac, Professor Mansfield Merriman of Lehigh University, Ainsworth R. Spofford, Librarian of Congress, Professor M. W. Harrington, ex-chief of the United States Weather Bureau, and others of equal promience, with Rear-Admiral Stephen B. Luce as naval editor and Professor James Mercur of West Point as military editor. Such names as these are a sufficient guarantee of the excellence of the entire work. In every article of importance the first thing that strikes the reader is the pronunciation and the etymology, both of which are often of great importance, and when presented in the simple, clear and easily understood form in which they occur here it is a matter of great convenience and satisfaction to the ordinary student. The mode of treatment of the subjects is such as makes the articles the most generally useful, purely technical treatises having been carefully avoided. But perhaps the highest praise is to be bestowed on another quality, particularly valuable in this age of rapid progress, viz: the fact that an especial effort has been made to bring the record of facts in all articles up to date. In this respect we know of no work of its kind that can compare with it. A marked departure from general custom in cyclopædias is the inclusion among the biographies of brief sketches of noted living men and women. Finally, every important article is accompanied by copious bibliographical information, enumerating the best works in which to pursue the subject further. These are generally limited to English works, either original or translated, and, although this rule is departed from in several instances, the notices are often on this account unsatisfactory, because the literature of many subjects (especially in the domain of military matters), giving the latest and |