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ENGINEER DEPARTMENT, UNITED STATES ARMY, 
 
 PROFESSIONAL NOTES 
 
 CAPTAIN EDWARD MAGUIRE, 
 
 CORPS OF ENGINEERS, U. S. A. 
 
 WASHINGTON: 
 
 GOVERNMENT PRINTING OFFICE. 
 
 1884. 
 
ENGINEER DEPARTMENT, UNITEOTATES ARMY, 
 
 PKOFESSIONAL NOTES 
 
 THB ' ^ 
 
 TJ'NIVEESITY 
 
 CAPTAIN EDWARD MAGUIRE, 
 
 CORPS OF ENGINEERS, U. S. A. 
 
 16100 
 
 WASHIJSTGTOST: 
 
 GOVERNMENT PRINTING OFFICE. 
 1884. 
 
OFFICE OF THE CHIEF OF ENGINEERS, 
 
 UNITED STATES ARMY, 
 Washington, D. C., May 20, 1884. 
 
 SIR : Capt. Edward Maguire, Corps of Engineers, has submitted to this 
 office a short series of papers containing information procured by him 
 while on leave of absence in Europe during the summer of 1883. 
 
 The papers contain information which it is thought will be useful to 
 officers of the Army generally, and I respectfully recommend that author- 
 ity be granted to have them printed, with the accompanying plates, at the 
 Government Printing Office, and that 1,000 copies be obtained for the 
 Engineer Department upon the usual requisition. 
 The papers are transmitted herewith. 
 
 Very respectfully, your obedient servant, 
 
 JOHN NEWTON, 
 Chief of Engineers, Brigadier and Brevet Major General. 
 
 Hon. ROBERT T. LINCOLN, 
 
 Secretary of War. 
 
 Approved. 
 
 By order of the Secretary of War : 
 
 JOHN TWEEDALE, 
 
 Chief Clerk. 
 r AR DEPARTMENT, May 28, 1884. 
 
CONTENTS. 
 
 Page. 
 
 Perforation of Armored Walls 8 
 
 Remaining Velocity IS 
 
 Vienna Electrical Exposition, 1883 21 
 
UNITED STATES ENGINEER OFFICE, 
 
 Buffalo, N. F., December 24, 1883. 
 
 GENERAL : I have the honor to forward herewith a short series of 
 papers containing information procured by me while on leave of absence 
 in Europe during last summer. 
 
 I submit them simply as possible additions to the professional notes 
 collected in the office of the Chief of Engineers. The subjects of which 
 they treat were interesting to me, and I hope may prove so to some one 
 else. 
 
 I found that an officer traveling in Europe without official letters has 
 but few opportunities of seeing or learning anything of military or any 
 other governmental work. 
 
 I am indebted for politeness to Geheim-Finanzrath Glaus Kopcke and 
 to Wasserbau-Director M. W. Schmidt, of Saxony ; to Capt. I. Trauzl, 
 formerly of the Austrian Engineers, and to the secretary of the American 
 legation at Paris. To our minister to Austria, Judge Alphonzo Taft, I 
 am particularly indebted for great courtesy. He did all that he could to 
 assist me in making ray visit to Vienna profitable and pleasant. 
 Very respectfully, your obedient servant, 
 
 EDW. MAGUIRE, 
 Captain of Engineers , U. S. A. 
 To the CHIEF OF ENGINEERS, U. S. A., 
 
 Washington, D. C. 
 
PERFORATION OF ARMORED WALLS. 
 
 [From the French of M. Rodier, capitaine d'artillerie de la marine, 1882.] 
 
 The English and French formulae for the perforation of armored walls 
 are given in Vol. Ill of the Memorial de P Artillerie de la Marine, 1875, 
 pp. 84 et seq. 
 
 They are accompanied by 
 
 (1 .) Tables containing numerical data and results of computations, which 
 are useful for solving problems relating to the perforation of walls. 
 
 (2.) Three plates of curves giving graphical solutions of a great num- 
 ber of problems. 
 
 (3.) Numerous examples of the use of the curves and tables. 
 
 Since that time numerous experiments have tieen made in France by the 
 Department of the Marine and progress has been made. At the Polygon 
 of Gavre the thickness of wrought-iron plates, which in 1875 did not 
 exceed 30 centimeters, has since attained 44 centimeters, and in the firings 
 the ratio of the thickness of the plate -to the diameter of the projectile has 
 risen from 1 to 1.5. Furthermore, guns of greater caliber than those em- 
 ployed up to that time'have been adopted. Finally, metallurgical indus- 
 try has made great advances in the manufacture of plates as well as in 
 that of projectiles. 
 
 The new conditions of fire against armored walls have led Mons. Helie 
 to modify somewhat the constants of the formula for perforation in use at 
 Gavre, and so the curves and tables mentioned above are no longer entirely 
 in accordance with the actual state of things ; furthermore, they are not 
 sufficiently extended, to be serviceable in every case which may arise in 
 consequence of the increase in the caliber of the guns and in the thickness 
 of the plates. 
 
 We will give, under a new and simple form, tables, to replace the former 
 ones, deduced from the results of the most recent experiments at Gavre, 
 and which apply to all thicknesses of plates and all calibers of guns actu- 
 ally in use. 
 
 The following will explain the method pursued in the calculations of the 
 tables. 
 
10 
 
 It is known that the various formulae for the perforation of isolated 
 plates, of backed plates, and of even wood walls may be placed under the 
 following form : 
 
 v V 2 
 
 - = K.E* 
 
 a 
 in which 
 
 p = the weight of the projectile. 
 
 V = that component of the velocity of the projectile which is 
 
 normal to the plate at the point of impact. 
 a = the diameter of the projectile. 
 
 E = the thickness of the plate. 
 
 K and x = two quantities to be determined by experiment and which 
 
 depend upon the form of the head of the projectile, and 
 
 on its quality as well as upon the quality of the plate. 
 
 If, now, we represent by n the ratio of the weight of the projectile to 
 
 that of a spherical shot of the same caliber, the formula becomes 
 
 n V 2 a 2 = K' E* 
 
 from which we see that with reference strictly to the perforation of plates 
 of the same thickness, 
 
 (1.) For projectiles having the same form of head the product -\/"~n Va 
 is constant. 
 
 (2.) For similar projectiles ( n constant) the product Va is constant; that 
 is to say, the velocity is inversely proportional to the caliber. 
 
 It is, then, evident that if in a table we write in the first column the 
 increasing thicknesses of the plates, and opposite to them the velocities 
 necessary for a projectile of 1 decimeter, for example, to perforate plates 
 having those tabular thicknesses, we may by simple divisions obtain the 
 velocities necessary for a similar projectile of any caliber whatever to 
 perforate the same thicknesses. 
 
 Conversely, knowing the thickness of the plate and the caliber, we may 
 obtain the velocity. 
 
 We may also just as simply obtain the caliber, knowing the velocity. 
 
 That being the case, we will examine, in reference to the ogivo-cylin- 
 drical projectiles of the Navy, which may be considered as similar, the case 
 of different walls which may be encountered, and we will give for each an 
 example of the use of the tables, so as to pass in review the different 
 problems which may present themselves for solution. 
 
 But first we will recall the two following hypotheses, verified by experi- 
 ments at least within the limits of practice, and which are useful for the 
 solution of problems of perforation. 
 
11 
 
 (1.) The resistance of a wall is independent of the velocity of the pro- 
 jectile, so that the perforation should in all cases absorb the same amount of 
 living force. Thus F being the velocity of impact, W the velocity neces- 
 sary strictly for perforation, U the velocity remaining after the perfora- 
 tion, we have 
 
 F 2 = W 2 + U 2 . 
 
 (2.) When a shot having a velocity, F, strikes a wall in a direction 
 making with the normal an angle, i, the normal component of the velocity 
 is F cos. i. If V be the normal velocity necessary strictly for perfora- 
 tion, the shot will pass through the wall only when 
 
 Fcos. i> F. 
 
 In what is to follow, weights will be expressed in kilogrammes, veloc- 
 ities in meters, the thicknesses and diameters in decimeters. 
 
 "We may, without appreciable error, substitute for the diameter of the 
 shot the caliber of the gun. 
 
 Finally we will assume N= 2.80. It is generally assumed, it is true^ 
 that the weight of the ogival projectile is three times that of the spherical 
 shot of the same caliber, the latter being the ordinary cast-iron shot of an 
 average density of 7.1. That is true for medium calibers if we suppose 
 the spherical shot to have a windage equal to that formerly assumed for 
 spherical shot of smooth-bore guns. But if we suppose the diameter of the 
 spherical shot to be exactly equal to the caliber of the gun the ratio of the 
 weights descends from 3.0 to 2.80. 
 
 In what follows steel or compound armor will not be considered, the 
 data at hand, even at the present time, not being sufficient for the deduc- 
 tion of a law of penetration. 
 
 1. UXARMORED WOOD WALLS. 
 
 The first experiments made at Gavre with ogival shot on an oak wall 
 and with a 14-centimeter gun, gave rise to the following formula : 
 
 pU 2 
 
 a 
 
 = 9025 E\ 
 
 which is still used by the Commission of Gavre. 
 
 Applying this formula to the 10-centimeter gun, and assuming p = 2.80 
 times the weight of a spherical shot of the same caliber, we have 
 
 U= 29.44 E. 
 
 Table No. 1 contains for every 5 centimeters of the value of E, from 1 
 to 1 2 decimeters, the corresponding values of U and U 2 . 
 
12 
 
 Examples of the use of Table No. 1 . 
 
 (1.) Required the caliber of theogival projectile capable of strictly per- 
 forating, in a normal direction, with a velocity of impact of 350 meters, a 
 wood wall 8 decimeters thick. 
 
 Let a be the caliber sought expressed in decimeters. 
 
 According to the table the wall in question is perforated by the project- 
 ile of 1 decimeter caliber, when the latter has a normal velocity of 235.5 
 meters. 
 
 We have, then, 
 
 a X 350 = 235.5 X 1 
 
 a = 0.673 decimeter. 
 
 (2.) Required the velocity necessary for a 24-centimeter ogival pro- 
 jectile to perforate normally and successively two wood walls 70 and 
 centimeters thick, respectively. 
 
 The velocities U' and U" necessary for the 1-decimeter projectile 
 pass through each of those walls are given in Table No. 1 . 
 
 To successively pass through the two walls that projectile should hav< 
 a velocity given by the formula 
 
 " 5 
 
 U= j/U' 2 + Ef 
 
 since the living force expended in the passage is independent of the ve- 
 locity. 
 
 Hence it results that the 24-centimeter projectile requires a velocity 
 
 ~2A~ 
 
 As Table No. 1 contains the values of U 2 the result is almost immedi- 
 ate, and we find 
 
 x = 140 meters. 
 
 (2.) WROUGHT-IRON ARMOR PLATES. 
 
 It is a well known fact that the depth of penetration of a projectile in 
 a medium of very great thickness is less than that thickness of the same 
 medium which can be strictly perforated by the same projectile. For this 
 reason, in determining the thickness to be given to an earthen parapet, it 
 is a generally admitted rule that the thickness should be 1.5 times the 
 penetration in the earth forming the parapet. The thickness to be given 
 to wood walls in order that the projectile may be completely arrested ij 
 1 J times the penetration of that projectile. 
 
 It is known, further, that the living force necessary for a projectile 
 perforate a plate with a backing is greater than the sum of the livii 
 forces required for the perforation of each separately. 
 
13 
 
 In firing at an armored wood wall it is difficult to determine exactly the 
 increase of resistance due to the union of the plate and backing; but 
 generally the resistance of the wood is very small in comparison to that 
 of the armor, and we may, with sufficient accuracy, assume as the resist- 
 ance of the plate the difference between the total resistance of the wall and 
 the known resistance of the wood-backing supposed isolated. 
 
 That is the method constantly employed by the Commission of Gavre. 
 
 Assuming such to be the case, now, if we consider armored wood walls, 
 the resistance of which has been determined at Gavre, and after having 
 deducted the resistance of the backing, we calculate the coefficients K and 
 x of the formula 
 
 a 
 
 We may form the following table : 
 
 Thickness of plates in decimeters 
 
 1 . 2 
 
 1.5 
 
 2.0 
 
 2.2 
 
 2.5 and 3.0 
 
 Values of x 
 
 1 .71 
 
 I. 5 8 
 
 1 .44 
 
 1.40 
 
 1.36 
 
 Values of K . 
 
 
 
 
 
 
 I0 3 
 
 
 
 
 
 
 Monsieur Helie satisfied these different results by the following for- 
 mula : 
 
 V V 2 
 
 = 2755600 E 3 
 
 But the results since obtained with the 44-centimeter plate have led to 
 a slight modification of the coefficients and to assuming definitively 
 
 Assuming as before a 1 decimeter and p = 2.80 times the weight of 
 a spherical shot of the same caliber, we shall have 
 
 V= 506.7 E ' 7 
 
 by means of which we have calculated Table No. 2. 
 
 It happens sometimes that the armor consists of several superposed 
 plates. Let E f , E", E'" be the thicknesses of the plates composing the 
 armor, V, V", V" the velocities with which the projectile perforates each 
 plate supposed isolated, Fthe velocity which the projectile should have to 
 perforate the armor. 
 
 Assuming that the living force necessary for the perforation of the armor 
 is equal to the sum of the living forces necessary for the perforation of 
 each of the individual plates, we shall have 
 
 Y 2 V f2 4- V" 2 -\- V'" 2 
 
 But this expression will give too small a value for F, for the reason that 
 no account is taken of the relations which in an armored wall exist between 
 
14 
 
 the different parts ; if those relations are unimportant in so far as they con- 
 cern the backing or the thin iron plates which form the frames on account 
 of their feeble resistance, such is not the case when we consider the plates 
 themselves. 
 
 In the most ordinary case the armor is composed of only two plates; the 
 comparative experiments made at Gavre with 32-centimeter projectiles on 
 44-centimeter plates and on two 22-centimeter plates united by a system 
 of bolts supply the data for calculating the thickness of a single plate, 
 equivalent to a system of two superposed plates. 
 
 Let 
 
 E f , E" = the thickness of the two plates 
 E = the thickness of the single plate. 
 
 Monsieur Helie, taking the results of the above-mentioned experiments, 
 deduced the following formula: 
 
 E=(E' + E") (10.102') 
 
 which is to be used for the case of an armor formed of two superposed 
 plates. 
 
 Examples of the use of Table No. 2. 
 
 (1.) Required the thickness of a wrought-iron plate which can be strictly 
 perforated by a 42-centimeter ogival projectile, having a normal velocity 
 of impact of 455 meters. 
 
 This 42-centimeter projectile should have the same perforative force as 
 a 10-centimeter projectile having a velocity, 
 
 F=455 X 4.2 = 1911 meters. 
 
 Table No. 2 gives 67 centimeters as the thickness sought. 
 
 (2.) Required the velocity of impact necessary for a 27-centimeter ogi- 
 val projectile to pierce a 20-centimeter wrought-iron plate under an angl< 
 of incidence of 30. 
 
 For a 1 -decimeter projectile this velocity is equal to 
 
 823 xJ_ r = 960.1. 
 cos. 30 
 
 We have then the equation 
 
 x X 2.7 = 960.1. 
 Hence 
 
 x = 355 meters. 
 
 (3.) Required the thickness of a single plate having the same resistan< 
 as three superposed plates of the respective thicknesses of 30 centimeters, 
 centimeters, and 20 millimeters. 
 
15 
 
 We commence by determining, by means of the formula given above, 
 the thickness of a single plate having the same resistance as two plates of 
 30 centimeters and 20 centimeters thickness, respectively. The calcula- 
 tion gives 4.66 decimeters as the required thickness. 
 
 According to Table No. 2 the 10-centimeter shot should have a velocity 
 of 1,488 meters to pierce a plate of 4.66 decimeters, and a velocity of 164 
 meters to pierce a plate of 20 millimeters thickness. 
 
 Let V represent the velocity necessary for the same projectile to per- 
 forate the system of the three plates, and we have without sensible error, 
 on account of the comparatively feeble resistance of the third plate, 
 
 F 2 =(1488) 2 + (164) 2 = 2241040, 
 and hence 
 
 V= 1497 meters. 
 
 From Table No. 2 we see that a 47-centimeter plate is equivalent to an 
 armor composed of the three plates of 30 centimeters, 20 centimeters, and 20 
 millimeters thickness. 
 
 3. ARMORED WALLS. 
 
 The resistance of an armored wall being equal to the sum of the resist- 
 ances of its component parts, we may by means of the tables which give 
 the resistances of the different parts, obtain the total resistance of the wall. 
 
 Among the different armored walls in use at Gavre there is a type known 
 specially as the " Gavre Wall," and which consists of a wood wall 84 cen- 
 timeters thick, protected by armor plates. This wall is one of the strong- 
 est and most frequently used in the experiments. 
 
 It has been deemed advisable, therefore, to calculate by means of Tables 
 Kos. 1 and 2 a third table (No. 3) of perforations of this wall for every 
 centimeter of thickness of plates from 1 decimeter to 1 meter by a 1 -deci- 
 meter projectile whose weight is 2.80 times that of a spherical shot of the 
 same caliber. 
 
 The velocities thus calculated will generally be a little greater than those 
 necessary for the perforation of armored walls with wood backing assem- 
 bled and framed in iron under the condition of taking into account the 
 thickness of the frame. Consequently the use of Table No. 3 may be ex- 
 tended to the armored sides of ships without fear of underestimating. It 
 may be extended also to walls whose armor is formed of several plates 
 directly superposed or separated by a wood filling, but in those cases it will 
 be necessary to substitute for the superposed plates the single plate which 
 has the same resistance. 
 
 Examples of the use of Table No. 3. 
 
 (1.) Required the velocity necessary for a 37-centimeter ogival projectile 
 to perforate a ship's side protected by a 45-centimeter wrought-iron plate. 
 
16 
 
 According to Table, No. 3 the 1 -decimeter projectile requires for this per- 
 foration a velocity of 1,473 meters. The velocity sought is then 
 
 n = 398.1 meters. 
 
 (2.) Required the thickness of armor of a wall which will be strictly per- 
 forated in a normal direction by a 37-centimeter projectile having a velocity 
 of 398 meters. 
 
 The thickness is that corresponding to a velocity of 398 X 3.7 = 1473 
 meters for a 10-centimeter shot, that is to say, according to the table, 45 
 centimeters. 
 
 (3.) Required the velocity necessary for a 34-centimeter ogival projectile 
 to perforate normally an armor of superposed plates of 30 centimeters, 20 
 centimeters, and 20 millimeters thicknesses. 
 
 We commence by determining, by the process indicated in the preceding 
 paragraph (third example), the thickness of a single plate having the same 
 resistance as the three plates. The calculation gives 47 centimeters as the 
 thickness sought. 
 
 According to Table No. 3 the velocity necessary for the 10-centimeter' 
 projectile to perforate a wall whose armor is 47 centimeters thick, is 1,517 
 meters. The velocity sought is then 
 
 = 446.2 meters. 
 
 The tables are calculated for the oblong projectiles in use in the French 
 Navy, whose weights are on an average 2.80 times those of spherical shot 
 of the same calibers, but they may easily be extended to all oblong projec- 
 tiles of any weight whatever by means of the remark given above. 
 
 " 1 . For projectiles having the same form of head the product V n Va is 
 constant." 
 
 The product i/n Va being in effect constant for the same thickness of 
 plate perforated, it results that, to solve the problem, it is sufficient to con- 
 sider the projectile as one of those in use in the French Navy, and then 
 
 /2~8 
 multiply the result thus obtained by -J - - if it be a question of velocity 
 
 or caliber. If, on the contrary, it be a question of thickness of wall, we 
 must first multiply the velocity by ^j ; and then make use of the 
 
 tables as if we had to do with a French naval projectile. 
 
 In order to facilitate the calculations by a rapid determination of n, we 
 have given in Table No. 4 the weights of spherical shot for each centimeter 
 of caliber from 10 to 45 centimeters. 
 
 
17 
 
 In order to calculate the penetration of a projectile for any range we 
 must determine its velocity of impact at that range, and for that purpose 
 must make use of the tables or formulae for remaining velocities. 
 
 TABLE No i. -WOOD WALLS. 
 
 Values of 
 
 Values of 
 
 Values of 
 
 Values of 
 
 Values of 
 
 Values of 
 
 E, in 
 
 U, in 
 
 U*, in 
 
 , in 
 
 7, in 
 
 t/ 2 , in 
 
 decimeters. 
 
 meters. 
 
 meters. 
 
 decimeters. 
 
 meters. 
 
 meters. 
 
 .0 
 5 
 
 29.44 
 44.16 
 
 867 
 Z ,95Q 
 
 7.0 
 7-5 
 
 206. i 
 
 220.8 
 
 42,477 
 48,752 
 
 .0 
 
 58.9 
 
 3.467 
 
 8.0 
 
 2 35-5 
 
 55,46o 
 
 5 
 
 '. - 
 
 ll:l 
 
 5,417 
 7,800 
 
 85 
 9.0 
 
 250.2 
 264.9 
 
 62,600 
 70,172 
 
 5 
 
 103.0 
 
 10 , 609 
 
 9-5 
 
 279.7 
 
 78,232 
 
 t .0 
 
 117.7 
 
 '3,853 
 
 10. 
 
 294.4 
 
 86,671 
 
 5 
 
 132.5 
 
 *7,556 
 
 10.5 
 
 309.1 
 
 95,543 
 
 5-o 
 
 147.2 
 
 21,668 
 
 II. 
 
 323.8 
 
 104,846 
 
 1;! 
 
 161. 9 
 176.6 
 
 26,211 
 31,187 
 
 "5 
 
 12.0 
 
 338.5 
 353-2 
 
 114,582 
 124,750 
 
 6.5 
 
 i9 I -3 
 
 36,596 
 
 
 
 
 TABLE No. 2.-WROUGHT-IRON ARMOR-PLATES. 
 
 Values of 
 , in 
 decimeters. 
 
 Values of 
 F, in 
 meters. 
 
 Values of 
 F, in 
 meters. 
 
 Values of 
 E, in 
 decimeters. 
 
 Values of 
 F, in 
 meters. 
 
 Values of 
 y\ in 
 meters. 
 
 s 
 
 5^ 
 
 2, 601 
 
 S-i 
 
 ,585 
 
 ,512,225 
 
 .2 
 
 164 
 
 26,896 
 
 5-2 
 
 ,607 
 
 ,582,449 
 
 3 
 
 218 
 
 47,524 
 
 5-3 
 
 ,628 
 
 ,650,384 
 
 4 
 
 267 
 
 71,289 
 
 5-4 
 
 ,650 
 
 ,722,500 
 
 . 5 
 
 312 
 
 97,344 
 
 5-5 
 
 ,6 7 
 
 ,792,241 
 
 .6 
 
 354 
 
 
 5-6 
 
 ,692 
 
 ,862,864 
 
 7 
 
 395 
 
 156,025 
 
 5-7 
 
 ,713 
 
 ,934,369 
 
 .8 
 
 433 
 
 187,489 
 
 5-8 
 
 ,734 
 
 3,006,756 
 
 9 
 
 .0 
 
 507 
 
 221,841 
 257,049 
 
 5-9 
 6.0 
 
 ,755 
 ,776 
 
 3,080,025 
 3,154,176 
 
 . i 
 
 542 
 
 293,764 
 
 6.1 
 
 ,797 
 
 3,229,209 
 
 .2 
 
 576 
 
 331,776 
 
 6.2 
 
 ,817 
 
 3,301,489 
 
 3 
 
 609 
 
 370,881 
 
 6-3 
 
 ,838 
 
 3,378,244 
 
 4 
 
 641 
 
 410,881 
 
 6.4 
 
 ,858 
 
 3,452,164 
 
 5 
 
 673 
 
 452,929 
 
 6-5 
 
 ,878 
 
 3,526,884 
 
 .6 
 
 704 
 
 495,616 
 
 6.6 
 
 ,898 
 
 3,602,404 
 
 7 
 
 736 
 
 . 541,696 
 
 6-7 
 
 ,918 
 
 3,678,724 
 
 .8 
 -9 
 
 765 
 794 
 
 585,225 
 630,436 
 
 6.8 
 6.9 
 
 ,939 
 ,959 
 
 3,759,72i 
 3,837,681 
 
 .0 
 
 823 
 
 677,329 
 
 7.0 
 
 ,978 
 
 3,912,484 
 
 .1 
 
 852 
 
 725,904 
 
 7.1 
 
 ,998 
 
 3,992,004 
 
 .2 
 
 880 
 
 774,400 
 
 7-2 
 
 ,018 
 
 4,072,324 
 
 3 
 
 908 
 
 824,464 
 
 7-3 
 
 ,037 
 
 4,149,369 
 
 4 
 
 935 
 
 874,225 
 
 7-4 
 
 ,057 
 
 4,231,249 
 
 . c 
 
 962 
 
 925,444 
 
 7 * 5 
 
 ,076 
 
 4,309,776 
 
 .6 
 
 989 
 
 978,121 
 
 7.6 
 
 ,096 
 
 4,393,216 
 
 7 
 
 .8 
 
 ,015 
 ,042 
 
 ,030,225 
 ,085,764 
 
 n 
 
 ,"5 
 , I 34 
 
 4,473,225 
 4,553,956 
 
 9 
 
 ,068 
 
 ,140,624 
 
 7-9 
 
 ,153 
 
 4,635,409 
 
 3- 
 
 ,93 
 
 ,194,649 
 
 8.0 
 
 .172 
 
 4,717,584 
 
 3- 1 
 
 ,119 
 
 ,252, 161 
 
 8.1 
 
 ,191 
 
 4,800,481 
 
 3-2 
 
 ,144 
 
 ,308,736 
 
 8.2 
 
 ,210 
 
 4,884,100 
 
 3-3 
 
 ,168 
 
 ,364,224 
 
 8-3 
 
 ,229 
 
 4,968,441 
 
 3-4 
 
 IQ3 
 
 ,423,249 
 
 8.4 
 
 ,2 4 8 
 
 5,053,504 
 
 3-5 
 
 ,218 
 
 ,483,524 
 
 8-5 
 
 ,266 
 
 5,134,756 
 
 3-6 
 
 ,242 
 
 ,542,564 
 
 8.6 
 
 ,285 
 
 5,221,225 
 
 3-7 
 
 ,266 
 
 ,602,756 
 
 8-7 
 
 ,304 
 
 5,308,416 
 
 3-8 
 
 ,290 
 
 ,664,100 
 
 8.8 
 
 ,322 
 
 5,391,684 
 
 3-9 
 
 
 ,726,596 
 
 8.9 
 
 ,340 
 
 5,475,600 
 
 4.0 
 
 ',337 
 
 ,787,569 
 
 9.0 
 
 ,359 
 
 5,564,881 
 
 
 ,36o 
 
 , 849 , 600 
 
 9.1 
 
 ,377 
 
 5,650,129 
 
 4-2 
 
 ,383 
 
 ,912,689 
 
 9.2 
 
 ,395 
 
 5,736,025 
 
 4-3 
 
 ,407 
 
 ,979,649 
 
 9-3 
 
 
 5,827,396 
 
 4.4 
 
 ,429 
 
 ,042,041 
 
 9-4 
 
 !432 
 
 5,914,624 
 
 4-5 
 
 ,452 
 
 ,108,304 
 
 9-5 
 
 ,45 
 
 6 , 002 , 500 
 
 4.6 
 
 ,475 
 
 ,175,625 
 
 9.6 
 
 ,468 
 
 6,091,024 
 
 4-7 
 
 ,497 
 
 ,241,009 
 
 9-7 
 
 ,486 
 
 6,180,196 
 
 4.8 
 
 ,519 
 
 ,307,361 
 
 9.8 
 
 ,504 
 
 6,270,016 
 
 4.9 
 
 
 ,442,969 
 
 9.9 
 
 ,522 
 
 6,360,484 
 
 
 $3 
 
 
 10. 
 
 ,540 
 
 6,45* ,600 
 
 16100- 
 
18 
 
 TABLE No. 3. ARMORED WALLS. 
 
 Values of 
 
 Values of 
 
 Values of 
 
 Values of 
 
 Values of 
 
 Values of 
 
 , in 
 
 F, in 
 
 E , in 
 
 F. in 
 
 E, in 
 
 r, in 
 
 decimeters. 
 
 meters. 
 
 decimeters. 
 
 meters. 
 
 decimeters. 
 
 meters. 
 
 .0 
 
 564 
 
 4.1 
 
 ,382 
 
 7.2 
 
 ,033 
 
 .1 
 
 595 
 
 4.2 
 
 ,405 
 
 7-3 
 
 ,052 
 
 .2 
 
 627 
 
 4-3 
 
 ,428 
 
 7-4 
 
 ,072 
 
 3 
 
 658 
 
 4-4 
 
 ,450 
 
 7-5 
 
 ,091 
 
 4 
 
 687 
 
 4-5 
 
 ,473 
 
 7-6 
 
 ,110 
 
 .5 
 
 717 
 
 4.6 
 
 ,495 
 
 7-7 
 
 ,129 
 
 .6 
 
 746 
 
 4-7 
 
 ,517 
 
 7.8 
 
 ,148 
 
 7 
 
 767 
 
 4-8 
 
 ,539 
 
 7-9 
 
 ,167 
 
 .8 
 
 804 
 
 4.9 
 
 ,56o 
 
 8.0 
 
 ,186 
 
 9 
 
 832 
 
 5-0 
 
 ,582 
 
 8.1 
 
 ,205 
 
 .0 
 
 859 
 
 
 ,604 
 
 8.2 
 
 ,224 
 
 . i 
 
 887 
 
 5-2 
 
 ,626 
 
 8-3 
 
 ,243 
 
 .2 
 
 914 
 
 5-3 
 
 ,647 
 
 8-4 
 
 ,262 
 
 3 
 4 
 
 967 
 
 5-4 
 5-5 
 
 ,668 
 ,689 
 
 8-5 
 8.6 
 
 ,280 
 ,298 
 
 5 
 
 993 
 
 5-6 
 
 ,710 
 
 8-7 
 
 
 .6 
 
 ,019 
 
 5-7 
 
 
 8.8 
 
 !335 
 
 7 
 
 ,045 
 
 5-8 
 
 ^752 
 
 8.9 
 
 ,353 
 
 .8 
 
 ,071 
 
 5-9 
 
 ,772 
 
 9.0 
 
 ,372 
 
 9 
 
 ,096 
 
 6.0 
 
 ,793 
 
 9.1 
 
 ,39 
 
 3- 
 
 ,/2I 
 
 6.1 
 
 ,814 
 
 9-2 
 
 ,408 
 
 3.1 
 
 ,M6 
 
 6.2 
 
 ,834 
 
 9-3 
 
 ,426 
 
 3-2 
 
 ,I 7 
 
 6-3 
 
 ,854 
 
 9.4 
 
 ,444 
 
 3-3 
 
 ,194 
 
 6.4 
 
 ,874 
 
 9-5 
 
 ,462 
 
 3-4 
 
 ,218 
 
 6-5 
 
 ,894 
 
 9.6 
 
 ,480 
 
 l:l 
 
 ,242 
 ,266 
 
 6.6 
 6-7 
 
 ,934 
 
 9-7 
 9.8 
 
 ,498 
 
 3-7 
 
 ,290 
 
 6.8 
 
 ,954 
 
 9.9 
 
 ,'534 
 
 3-8 
 
 ,3 Z 3 
 
 6.9 
 
 ,974 
 
 IO.O 
 
 ,552 
 
 3-9 
 
 ,337 
 
 7.0 
 
 ,993 
 
 
 
 4.0 
 
 ,359 
 
 7- 1 
 
 ,013 
 
 
 
 TABLE No. 4. WEIGHTS OF SPHERICAL SHOT OF DIFFERENT CALIBERS. 
 
 Caliber in 
 decimeters. 
 
 Weight in 
 kilograms. 
 
 Caliber in 
 decimeters. 
 
 Weight in 
 kilograms. 
 
 Caliber in 
 decimeters. 
 
 Weight in 
 kilograms. 
 
 .0 
 
 3-718 
 
 2.2 
 
 39-585 
 
 3-4 
 
 146.114 
 
 .1 
 
 4.948 
 
 2-3 
 
 45-231 
 
 3-5 
 
 159.390 
 
 . 2 
 
 6.424 
 
 2.4 
 
 Si-39 1 
 
 3-6 
 
 I73-446 
 
 3 
 
 8.167 
 
 2 '5 
 
 58.086 
 
 3-7 
 
 188.305 
 
 4 
 
 IO.2OI 
 
 2.6 
 
 65-34 
 
 3-8 
 
 203.989 
 
 .5 
 
 12.546 
 
 2-7 
 
 73-173 
 
 3-9 
 
 220.522 
 
 .6 
 
 15.227 
 
 2.8 
 
 81.607 
 
 4.0 
 
 237.923 
 
 7 
 
 18.264 
 
 2.9 
 
 90.667 j 
 
 4-i 
 
 256.218 
 
 .8 
 
 21.680 
 
 3-o 
 
 100.374 i 
 
 4 2 
 
 275.426 
 
 9 
 
 25.499 
 
 3-i 
 
 110.749 j 
 
 4-3 
 
 295-572 
 
 .0 
 
 29.740 
 
 3-2 
 
 121.817 
 
 4.4 
 
 316.676 
 
 .1 
 
 34. 4 28 
 
 3-3 
 
 133-595 
 
 4-5 
 
 338.762 
 
 DETERMINATION OF A GENERAL FORMULA FOR REMAINING VE- 
 LOCITY, 
 
 In view of the discrepancies in the results given in the tables and by 
 the various formulae for remaining velocities, and also the complicated 
 form of the latter, it is difficult to decide as to which one to adopt. A 
 formula, simple in form and susceptible of quick and easy application, 
 which will give sufficiently approximate results, would appear to be de- 
 sirable. With this in view the following determination of such a formula 
 was made. 
 
 From the table of velocities, given on page 41 of Professional Papers 
 
19 
 
 No. 25, Corps of Engineers, United States Army, we will deduce the 
 equation for remaining velocity for each gun. Having obtained these 
 equations the general equation for all of the guns will be of the same 
 form as the individual equations, the coefficients being the means of those 
 of the latter. 
 
 For example, the table gives for the 100-ton Armstrong gun 
 
 Feet. 
 
 Velocity at mnzzle 1, 832 
 
 Velocity at 600 yards 1,765 
 
 Velocity at 1,200 yards 1,699 
 
 Velocity at 1,800 yards 1, 637 
 
 Velocity at 2,400 yards 1, 577 
 
 Velocity at 3.000 yards 1,518 
 
 Velocity at 3,600 yards 462 
 
 Velocity at 4,200 yards ,408 
 
 Velocity at 4,800 yards ,355 
 
 Velocity at 5,400 yards ,305 
 
 Velocity at 6,000 yards ,259 
 
 Now let 
 
 V the initial velocity, 
 v = the remaining velocity, 
 
 x = the range at which the projectile has a remaining velocity v. 
 Assume the general equation 
 
 v= F + Ax + Bx 2 . (I) 
 
 Substituting in this equation the values given above we shall have the 
 observation equations 
 
 1765=1832+ 600 A+ 360000 B 
 16991832 + 1200 A+ 1440000B 
 1637=1832+1800 A+ 3240000 B 
 1577=1832+2400A+ 5760000B 
 1518 1832+3000 A+ 9000000 B 
 14621832+3600 A+12960000 B 
 1408 1832+ 4200 A + 17640000 B 
 1355 1832 +4800 A +23040000 B 
 13051832 + 5400 A+29160000 B 
 1259 1832 + 6000 A+36000000B 
 
 Performing the necessary operations we shall obtain the following nor- 
 mal equations : 
 
 13791 138600 A + 653400000B 
 
 -644022 6534000 A+31831 568000 B 
 From which we have 
 
 j3 +0.000006 J 0.127 
 
 Substituting these values in the general equation (1) we have 
 
 v== V 0.127Z+0.000006Z 2 
 By a similar process we shall obtain a similar equation for each gun. 
 
20 
 
 The equations are : 
 
 For 100-ton Armstrong : 
 
 v= V 0. 
 For 81 -ton Woolwich : 
 
 v=V 0.111#+0.000006o; 2 
 For 38-ton Woolwich : 
 
 v= V 0.1252' -j-0.000006z 2 
 For 71 -ton Krupp : 
 
 v= V 0.114o;-j-0.000006^ 2 
 For 51 -ton Krupp: 
 
 v= V 0.121^4-0.000006^ 
 For 18-ton Krupp : 
 
 v= V 0.13l-|-0.000006a; 2 
 
 Taking the mean of these equations we have as the general equation 
 for all of the guns 
 
 v= V 0.12150? -f-0.000006a; 2 
 
 In order to compare the results given by this equation with those given 
 in the table on page 41 of Professional Papers No. 25, we have the follow- 
 ing table. The upper line opposite each gun gives the latter results while 
 the lower line gives the former. It will be seen that the results agree 
 quite closely : 
 
 TABLE OF VELOCITIES. 
 [Velocities in feet per second, x = Range in yards.] 
 
 Gun. 
 
 At 
 muzzle. 
 
 600 
 yards. 
 
 j 
 S 
 
 i 
 
 ,200 
 ards. 
 
 j 
 J 
 
 ,800 
 r ards. 
 
 
 .,400 
 r ards 
 
 3,000 
 yards 
 
 i 
 
 [,6oo 
 r ards. 
 
 i 
 
 3 
 
 ^200 
 
 rards. 
 
 4 
 5 
 
 ,800 
 ards. 
 
 e 
 
 i 
 
 , 4 oo 
 
 ards. 
 
 6, 
 ya 
 
 000. 
 
 rds 
 
 zoo-ton Armstrong, -j 
 
 1,832 
 
 ,765 
 ,761 
 
 
 ,699 
 ,695 
 
 
 ,637 
 , 6 33 
 
 
 ,577 
 ,575 
 
 ,5i8 
 ,5 22 
 
 
 ,462 
 ,472 
 
 
 ,408 
 ,428 
 
 
 ,355 
 
 ,387 
 
 
 ,305 
 ,3s 1 
 
 
 259 
 3!9 
 
 8i-ton Woolwich... -j 
 
 1.657 
 
 ,601 
 ,586 
 
 
 ,546 
 ,520 
 
 
 ,494 
 ,458 
 
 
 ,443 
 ,400 
 
 ,393 
 ,347 
 
 
 ,346 
 , 2 97 
 
 
 ,300 
 > 2 53 
 
 
 ,258 
 
 ,212 
 
 
 ,218 
 ,176 
 
 
 181 
 144 
 
 38-ton Woolwich. . . < 
 
 i,59o 
 
 
 ,5*8 
 
 ,519 
 
 
 ,449 
 ,453 
 
 
 ,33 
 ,39i 
 
 
 ,322 
 ,333 
 
 ,266 
 ,280 
 
 
 ,213 
 ,230 
 
 
 ,166 
 ,186 
 
 
 ,125 
 
 , J 45 
 
 
 ,089 
 ,109 
 
 
 058 
 077 
 
 yi-ton Krupp \ 
 
 1,703 
 
 ,646 
 
 6^2 
 
 
 ,59 
 egg 
 
 
 ,536 
 
 
 ,484 
 446 
 
 ,434 
 
 
 ,385 
 
 
 ,338 
 
 
 ,293 
 
 org 
 
 
 ,251 
 
 
 III 
 
 5i-ton Krupp -j 
 
 1,645 
 
 ,58o 
 
 
 ,5i7 
 508 
 
 
 ,457 
 446 
 
 
 ,399 
 088 
 
 ,344 
 
 
 ,292 
 2 8c 
 
 
 ,244 
 
 
 ,I 9 8 
 
 
 >*59 
 164 
 
 
 IT, 
 
 i8-ton Krupp -I 
 
 1,688 
 
 ,6x4 
 ,617 
 
 
 ,544 
 .55 1 
 
 
 ,477 
 ,489 
 
 
 ,412 
 ,43i 
 
 ,35i 
 ,378 
 
 
 , 2 94 
 ,328 
 
 
 ,241 
 ,284 
 
 
 ,192 
 ,243 
 
 
 ,i49 
 ,207 
 
 
 III 
 
 175 
 
 Capt. Orde Browne has given the following simple rule of thumb 
 " The penetration of projectiles into wrought iron is one caliber for evei 
 thousand feet of striking velocity." 
 
21 
 
 In the following table are given the penetrations for certain guns as de- 
 termined by Browne's rule, the striking velocities having been determined 
 by the general equation just deduced. Comparing the results there given 
 with those given in Professional Papers No. 25, the value of the rule may 
 be appreciated. 
 
 TABLE OF PENETRATIONS INTO WROUGHT IRON. 
 
 
 loo-ton 
 Armstrong. 
 
 8i-ton 
 Woolwich. 
 
 38-ton 
 Woolwich. 
 
 7 1 -ton 
 Krupp. 
 
 5i-ton 
 Krupp. 
 
 i8-ton 
 Krupp. 
 
 Caliber inches 
 
 
 
 
 
 
 
 RANGE. 
 
 
 
 
 
 
 
 At muzzle inches . . 
 
 32-52 
 
 26.51 
 
 19-87 
 
 26.82 
 
 23.03 
 
 J5-95 
 
 At 600 yards do . 
 
 31 .26 
 
 25.38 
 
 18 99 
 
 
 
 
 At i 200 yards do 
 
 
 
 x 18 16 
 
 24 66 
 
 
 
 
 At i, 800 yards do. 
 At 2,400 yards do. 
 
 28.99 
 27.96 
 
 23-33 
 22.40 
 
 I 7-39 
 16.66 
 
 23-69 
 22.77 
 
 20.24 
 J 9-43 
 
 14.07 
 
 At 3,000 yards ... . do . 
 
 27.01 
 
 21.55 
 
 16.00 
 
 21.94 
 
 18.69 
 
 13.02 
 
 At 3,600 yards . .. .do. 
 
 26. 13 
 
 20.75 
 
 15-38 
 
 21.15 
 
 17.99 
 
 12.55 
 
 At 4,200 yards do.. 
 
 25-35 
 
 20.05 
 
 14.82 
 
 20.46 
 
 17.36 
 
 12.13 
 
 At 4,800 yards ... .do.. 
 
 24.61 
 
 19.39 
 
 J 4-3 r 
 
 19.83 
 
 16.80 
 
 11.74 
 
 At 5,400 yards do . 
 
 23.98 
 
 18.82 
 
 3-86 
 
 19.25 
 
 16.29 
 
 11.40 
 
 At 6,000 yards do . . 
 
 23.41 
 
 18.30 
 
 '13.46 
 
 18.74 
 
 15-85 
 
 II. 10 
 
 VIENNA ELECTRICAL EXPOSITION, 1883. 
 
 I had laid my plans to visit Vienna at such a time after the opening of 
 the Electrical Exposition as to find it in full operation. I discovered, how- 
 ever, on reaching that city, that the opening day had been postponed to a 
 week later than my arrival. I therefore had but little time at my disposal 
 to devote to the Exposition. But even when it was opened the general dis- 
 play was comparatively small and, as far as the application of electricity 
 to military purposes is concerned, the variety of apparatus was very lim- 
 ited. The Austrian War Department was behindhand, and there was very 
 little that was new in its display. There was, it is true, a large assortment 
 of fuses and batteries, but they were all of well-known models. 
 
 There was, however, on exhibition one of Baron von Ebner's Light- 
 Projectors, and, in view of the important part which the electric light will 
 play in future operations of war, it is thought that a description of some 
 of the apparatus used for military purposes will not be out of place. 
 
 Fig. 1 is a drawing of von Ebner's apparatus. It consists of a large 
 parabolic concave mirror having an electric lamp in its luminous focus. 
 The lamp is connected with a spring clock-work at the back of the mir- 
 ror, by means of which the carbon points are kept at the proper distance 
 apart and the light thus regulated. 
 
 In order that there may be no loss of light through side radiation, a 
 Fresnel lens, L, with three circular prisms, is placed in front of the lamp, 
 and thus the rays are concentrated into a cylinder parallel to the axis of 
 the mirror. 
 
22 
 
 The mirror is supported by a strong iron frame on three wheels which 
 run around a central turning point. The iron circle UUU on which 
 the wheels run is divided into degrees in order to determine the horizon- 
 tal pointing. The apparatus is revolved by means of the arm G. 
 
 The vertical inclination of the mirror is produced by means of a crank 
 and endless screw, K K, which is geared into a toothed quadrant, Z. The 
 inclination may be read on a graduated half-circle, R, which is attached to 
 the right support. At the same place there is also a telescope clamped to 
 the horizontal limb, with its axis parallel to that of the mirror, thus mak- 
 ing it possible to observe the object illuminated by the mirror. 
 
 In 1878 experiments were made with such an instrument at Olmutz in 
 connection with the siege manoeuvres, and the results obtained were gen- 
 erally satisfactory, notwithstanding the fact that the light produced by an 
 Alliance machine was relatively of very small power. 
 
 The effectiveness of such large projectors is beyond question, and yet 
 they are more or less excluded from general use, partly on account of their 
 great cost and partly on account of the difficulty of moving them, due to 
 their great weight, five to six hundred weight. Furthermore, their size 
 renders the possibility of their being hit by an enemy's shot far from un- 
 certain. 
 
 For these reasons it is generally considered better to use small, handy 
 reflectors of but little weight, such as Mangin's, Sautter-Lemonier's, 
 Siernens's, &c., the positions of which may be constantly shifted, and con- 
 sequently the chances of being hit much reduced. 
 
 Mangin's projector, Fig. 2, contains, in a well-ventilated cast-iron case, 
 Tj T, the aplanatic mirror A, which is silvered on the convex side, and a 
 Sautter-Lemonier hand-lamp. On the front side at G is the projector- 
 frame closed either by a pane of glass with parallel faces, or by a divergent 
 lens. 
 
 The radii of curvature of the mirror, the power and refraction-co-efficient 
 of the glass having been determined by mathematical calculations there 
 was given to the mirror a rather large diameter, while at the same time 
 there is less spherical aberration than is ordinarily the case with spherical 
 mirrors of the same dimensions. 
 
 When the electric arc is placed in the luminous focus of the mirror a 
 beam of almost perfectly parallel rays passes out from the projector. If 
 the lamp be shifted from the luminous focus in either direction then the pro- 
 jector sends forth a divergent or only partially concentrated light. By the 
 use of the divergent lens the light may be dispersed for only the breadth 
 most frequently desired for lighting up the coast as well as surrounding 
 objects. The whole apparatus may be turned in any desired direction and 
 immediately clamped in any position. 
 
23 
 
 This projector intensifies the light nominally two thousand fold, which 
 amount, however, holds only for certain conditions and distances. 
 
 A full description of Siemens' projector is given in Sleeman's "Torpe- 
 does and Torpedo Warfare." 
 
 Comparative experiments made by the Imperial Royal Permanent Ar- 
 tillery Commission in Pola with the Mangin and Siemens projectors showed 
 that the latter caused a divergence of at least 5 40', while the Mangin ap- 
 paratus gave a divergence of only 2 to 4, as well as affording a somewhat 
 better use of the light. 
 
 Bustyn's Auxilliary Projector is intended to extend the illumination of 
 objects by a Mangin apparatus. By means of it pencils of light may be 
 turned off at any desired angle from the main beam, and, without percepti- 
 ble diminution of the latter, lateral objects can be illuminated and followed 
 at the same time as the main object. It consists essentially of a metal tube, 
 containing a plane mirror with a universal motion, placed in the side of 
 the projector. The light obtained by reflection illuminates objects lying 
 to the right or left of the main beam without interfering with the latter. 
 
 The following are some of the results obtained with a Mangin projector: 
 
 Experiments made at Fort Mont Valerien by a commission of French 
 officers showed that, with a light of 19,000 standard candle power in a 
 Mangin projector, houses, wagons, and military manoeuvres were plainly 
 visible at a distance of 5,000 meters. At a distance of 2,700 meters a sin- 
 gle soldier could be distinguished and observed at bayonet exercise. The 
 observer was in this case stationed near the projector. The lateral range 
 of the light is, however, very considerably increased if the observer station 
 himself at some distance from the instrument. 
 
 It was shown by experiments at Toulon that by the use of a divergent 
 lens a field 200 meters broad at a distance of 3,000 to 5,000 meters was 
 sufficiently illuminated to enable artillery to shoot into it. The barracks 
 at Mont Faron, a distance of 9,500 meters, could be seen from Toulon by 
 an observer standing near the projector. 
 
 The Sautter-Lemon ier hand-lamp, Fig. 3, consists of a metallic case, 
 g g, the upper plate of which makes an angle of 30 degrees with the 
 horizon. Perpendicular to the plate are a conducting-rod, Z Z, and a 
 spindle, A A ; the latter is turned by the wheel P>. The two carbon- 
 carriers K M, which are supported by the rod Z, may be moved up and 
 down on the spindle A by means of the nuts D D f . 
 
 In order to start the lamp the carbon points are first brought into con- 
 tact by turning the wheel B and then by a reverse motion separated to a 
 distance of 2 to 3 millimeters. An occasional movement of the carbon 
 points towards each other as they diminish by combustion is sufficient to 
 keep the light going. 
 
24 
 
 The lamp is arranged for uniform electrical currents. The positive 
 carbon travels for a single turn of the spindle A twice the distance moved 
 by the negative carbon, the thread of the nut D having twice the pitch of 
 that of D r . 
 
 The centering of the light-arc is accomplished by means of the screw C. 
 The upper or positive carbon may be given any desired position by means 
 of the articulations n and m of the carrier. 
 
 A small screen, S, of blackened plate-brass serves to intercept the cen- 
 tral ray; its proper place in the apparatus is fixed by means of a clamp 
 on the rod Z. 
 
 The conducting wires are inserted through the opening -\-p and a cor- 
 responding clamp-screw, p, on the opposite side. 
 
 In the section of the Exposition set aside for Denmark there was an 
 interesting display by the " First Division of the Royal Danish Torpedo- 
 Corps." I was not allowed to look at the detailed drawings, but I obtained 
 from the officer in charge of the apparatus the following general informa- 
 tion: 
 
 1. THE CURRENT-DISTRIBUTION TABLE FOR ELECTRICAL CONTACT 
 
 MINES. 
 
 All of the mines in one set are connected with the firing-battery on the 
 current-distribution table. The circuit is closed through the cable of the 
 mine struck by a hostile ship. The firing-battery is two-fold. A small 
 battery, the relay-battery, is connected with the cable when an attack is 
 expected. At the instant of contact it operates a firing-relay, which breaks 
 the relay-circuit, closes the direct firing-circuit, and then quickly breaks it 
 again after the charge is fired. The whole operation is automatic. Each 
 cable attached to the table is connected with a numbered dial, which indi- 
 cates the mine struck. 
 
 The relay-battery is connected with the mine by means of the armature 
 of the firing-relay. After the firing current has passed through the relay 
 the latter returns to a state of rest, when it closes a local circuit for a small 
 alarm-battery on the table : the bell connected with this latter battery 
 rings and announces a contact. 
 
 For testing the electrical condition of the mines and cables use is made 
 of a small testing-battery or several metal plates (carbon, copper, zinc) im- 
 mersed in sea-water, a delicate alarm, a galvanometer, and a test-circle, that 
 is to say, a circle of insulated contacts which can be connected with the 
 axis of the circle by means of a movable radial arm. 
 
 In order that several mines, arranged in a group, may be operated by 
 means of a single cable attached to the table, the branch-cable attached to 
 mine struck must be cut out of the system after the explosion. For this 
 purpose there is placed at the junction of the branch-cables a submarine 
 
 
25 
 
 relay whose armature is removed by a special cut-oat battery as soon as 
 the apparatus on the distribution table announces that an explosion has 
 taken place. The cut-out battery is connected with the cable by means of 
 a key firmly screwed to the table. If the key be pressed the cut-out bat- 
 tery is set in action through the connection established with the water in 
 consequence of the explosion and closes the submarine relay belonging to 
 it, by which means the corresponding cable is cut out of the system. 
 
 Leclanche" batteries, either with or without earthen cells, are used for 
 operating the mines. 
 
 2. SUBMARINE RELAY. 
 
 By means of this electro-magnetic relay a cable, after the explosion of 
 the mine to which it is attached, is cut out from the rest of the mines in 
 the same group and from the entire system. 
 
 This cutting out is effected by means of a revolving contact-ring, which 
 is held fast, when the relay is at rest, by a hook in such a manner that the 
 group and mine cables are connected with each other through the coil of 
 the relay. If the cut-out battery be set in action the armature of the relay 
 is attached, the hook is freed, and a spring turns the contact-ring whereby 
 the connection is cut out. 
 
 The relay stands in a water-tight box on the bottom of the sea. 
 
 3. CIRCUIT CLOSER. 
 
 The electrical circuit is ordinarily open in the sea-mine. A ship strik- 
 ing the mine closes the circuit by means of a circuit closer in the mine. 
 
 The closing is effected by means of about one cubic centimeter of mercury 
 situated in the bottom of a small iron cylinder which forms one contact. 
 The cover of the cylinder, which is insulated from it, forms the second con- 
 tact. This apparatus is suspended in the mine-case by chains. If the 
 ship upset the case the mercury runs out and makes the connection between 
 the two contacts. 
 
 4. PLATINUM-WIRE FUSE. 
 
 Platinum-wire fuses are used in the mines. The wire has a diameter of 
 -TJH to 2- tjtf millimeter, and can be brought to a red heat by a very light cur- 
 rent, only 0.05 to 0.07 ampere. 
 
 N 
 
 5. CARBON MINE. 
 
 The galvanized -iron mine-case and a carbon plate immersed in sea-water 
 constitute, with the connecting cable, a galvanic cell which is capable of 
 developing a current of sufficient strength to fire two of the fuses de- 
 scribed above. 
 
26 
 
 If the connection between the case and the carbon be maintained un- 
 broken the combination constitutes a simple contact mine. In this state 
 it is as dangerous to the defense as to the enemy. If, however, a polarized 
 relay be inserted between the carbon plate and the cables of all the mines 
 to be operated by it, the connections between the carbon and the mines may 
 be made or broken at will ; that is to say, the mines may be operated as if 
 they were ordinary non-automatic contact mines. A number of mines may 
 be operated by means of a single carbon plate. 
 
 The relay is therefore connected with the station by a leading cable. By 
 a positive current sent through the cable and the coil of the relay the cir- 
 cuit through the carbon and the mine is closed and by a negative current 
 it is opened. 
 
 By the aid of two plates (carbon and zinc), immersed in the water, and 
 a galvanometer, the electrical connection between the carbon and the mines 
 may be tested ; that is to say, the operator may determine with certainty 
 whether the mines are charged or discharged. 
 
 The apparatus (commutator, cut-out, tester, and galvanometer) needed 
 for the service and testing of the relay are arranged on the service table 
 for carbon mines. 
 
 6. CURRENT DISTRIBUTOR FOR OBSERVATION MINES AND COMBINED 
 OBSERVATION AND CONTACT MINES. TRUELSEN SYSTEM. 
 
 By the aid of this apparatus a large number of mines, especially obser- 
 vation mines, may be operated with only two cables. 
 
 At the bottom of the sea, in a water-tight iron case, lies a rheotome, 
 whose arm can, by means of a galvanic current from the station, be brought 
 into contact with the contact-plate corresponding to any particular mine. 
 That is done through the operating-cable. The arm stands in continue 
 contact with the firing-cable, so that the mine corresponding to the coi 
 tact-plate against which the arm presses may be exploded. 
 
 A test may be made of the correct position of the arm by means of tl 
 operating-cable and a system of resistance-coils ; a certain resistance coi 
 responds to each contact-plate. A similar system of resistance-coils, bt 
 in inverse order, is placed at the station. The sum of the two resistam 
 must always be the same when the arm is correctly placed. The resi* 
 auces are determined by a differential-galvanometer. 
 
 With several water plates (copper, carbon, zinc), the electrical conditioi 
 of the individual mines may be tested. 
 
 A dial at the station indicates the number of the contact-plate agaim 
 which the arm presses. 
 
 The following is a translation of a portion of an article by Dr. Fi 
 
27 
 
 Wachter, published in No. 23 of the " Internationale Zeitschrift fur die 
 Elektrische Ausstellung in Wien, 1883" : 
 
 The sea-mine apparatus of the Danish Navy consists of a large set of 
 very ingeniously combined, but also very complicated instruments. The 
 first to be mentioned is the current-distributor for observation, and com- 
 bined observation and contact mines. This apparatus, which is mounted 
 on a special table the current-distribution table operates a large num- 
 ber of mines by means of only two cables. 
 
 It consists of two similar current distributors, formed of as many con- 
 tact plates, arranged in a circular manner, as there are mines to be oper- 
 ated. Over the contact plates moves a metallic arm in such a manner that 
 it is never in contact with more than one plate at a time. Between each 
 two contact plates is inserted a resistance-coil of Siemens' units, but the 
 arrangement of the latter on the second distributor is in reverse order 
 from that on the first. 
 
 Suppose, now, the contact plates arranged in a circular manner on the 
 table and numbered from 1 to 30, from left to right; then we shall have 
 between Plates 1 and 2 on the first distributor a resistance coil of 1 Sie- 
 mens' unit ; between 2 and 3 a coil of 2 Siemens' units, &c. On the 
 ,second distributor the plates are numbered in the same order, but between 
 1 and 2 there is a coil of 31 Siemens' units ; between 2 and 3 a coil of 
 30 Siemens' units, &c. 
 
 The first distributor is on the current-distribution table at the obser- 
 vation-station ; the second is in a water-tight metal box on the bottom of 
 the sea. The two distributors are connected by the so-called "Afficirungs " 
 cable. If, now, the pointer at the observation-station be moved from the 
 contact-plate 2 to 25, then the pointer of the rheotome at the bottom of the 
 sea also moves from 2 to 25. In that case, then, only mine No. 25 is in 
 the circuit, all the others being cut out. It may happen that the pointer 
 jumps one or more contact-plates, or hitches, and in that case the number 
 25 of the station-distributor will not correspond to the same number of the 
 submarine rheotome, but to a higher or lower, or at all events, some un- 
 known number, and it would be necessary to raise the apparatus from the 
 bottom of the sea to set it right. But to avoid that infeasible operation the 
 above-mentioned resistance-coils between the contact-plates are used. 
 
 In consequence of the arrangement of the two distributors they must 
 offer a constant resistance, no matter on which number the pointers may 
 be, provided both are on the same number. If the pointers were on No. 
 5 the resistance would be 5 + 27 = 32 Siemens' units ; if on No. 8 the 
 resistance would be 8 -j- 24 = 32 Siemens' units, &c. Consequently a 
 constant battery would always give the same result on the galvanometer. 
 
28 
 
 As such a battery are used large copper and zinc plates immersed in sea- 
 water ; for measuring the strength of the current a differential-galvanom- 
 eter is used. ' 
 
 With these the rheotomes are tested from time to time. If a wrong re- 
 sult be given it shows that the two pointers are not on the same numbers. 
 In that case, by measuring the resistance, a calculation may be made of the 
 error of the submarine pointer without the necessity of raising the appa- 
 ratus. For such calculations a Siemens 7 universal-galvanometer is 
 mounted on the current-distribution table. 
 
z. 
 
14 DAY USE 
 
 RETURN TO DESK FROM WHICH BORROWED 
 
 LOAN DEPT. 
 
 o?iVS? d ie% e $&!* ESSU-S5- 
 
 Tel. No. 642-3405 
 
 
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 SEP IB 1976 
 
 LD21A-50m-2,'7l 
 (P200IslO)476 A-32 
 
 General Library 
 
 University of California 
 
 Berkeley 
 
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