And calculate the length of the "dangerous" space or error which can be allowed in estimating the distance, when 5.-What is the effect of the following projectiles on the unarmored side of a ship of the Shannon class? .65-inch Gatling bullet. 64-pdr. common shell. 64-pdr. shrapnell. 9-inch case. 6.-How are the perforating powers of guns compared in this country? In what ratio do the resisting powers of armor plates vary when fired at direct? 7.-What properties are most desirable in the iron for armor plates? What is the use of an iron skin? Explain the peculiarity of the Palliser armor bolt. 8.-Explain, with diagrams, the general distribution of the armor in the Dreadnought, Inflexible, and Nelson. 9.-In what plane is it necessary to lay the deck on which a turret revolves? Give reasons for your answer. Explain the method of marking a turret in degrees. 10.-Show how to calculate a correction table for concentrating slide guns. Investigate, in terms of (d) and (0), an expression for the error arising from using the table when trained before or abaft the beam (d being the distance from the center gun and the angle of training). Of what use are converging plates? 11.-Investigate an expression for the error in direction due to the sights being inclined, in terms of (0) the inclination of the sights and (a) the angle of elevation. 12. What adjustments are necessary when placing the director in position? Explain fully how to test their accuracy. 13.-Investigate the horizon method of determining the distance of an object. Are there any objections to its use? If so, what? GUNNERY LIEUTENANTS. (February, 1877.) FIRST PAPER. 1.—Explain the meaning of the terms "stress," "ultimate tensile strength," and "limit of elasticity." 2. Distinguish between cast iron and wrought iron. Give a brief description of a method of obtaining wrought iron. 3.-Define the term "steel." Distinguish as clearly and fully as time permits between wrought iron and steel. What have been hitherto the chief obstacles to an extended use of the latter? 4.—No possible thickness can enable a cylinder to bear a pressure from within greater on each square inch than the ultimate tensile strength of the material; prove this. 5.-Explain, with diagram, the principal parts of a 9" M. L. R. gun with two double coils. Describe the bushes with which guns are vented. How are vents examined? 6. With the uniform twist compare the pressure required to produce rotation with that necessary to give translation. Distinguish between uniform and increasing twist. Which absorbs the most work? 7.-Describe the elevating gear proposed for the guns of the Inflexible. What are its advantages? Point out the disadvantages of the capstan-head elevating gear. 8.—Explain, with a figure, the forces which act on the discharge of a gun mounted on a carriage and slide; also point out the advantage of a low carriage, 9.—When a charge of powder is exploded, what are the proportions by weight of gases and solid products? Give an outline of the method by which the volume of gas was determined. 10. Establish a relation between the pressure and density when a charge of powder is exploded in a closed vessel. 11.-Calculate the velocity of a projectile whose weight is 180 lbs. when fired from an 8" M. L. R. gun: 12.-What is the meaning of the term "factor of effect"? Explain fully the object of "air-spacing" the charge, and of chambering the gun. Fourteen days allowed for this question. Give your opinion about the mounting, working, and use of machine guns1. On board the ship. 2. In the boats. 3. In landing operations. GUNNERY LIEUTENANTS. (April, 1877.) FIRST PAPER. 1.-Explain the meaning of the terms elasticity and elastic limit, as applied to metals. How are they respectively measured? 2. Summarize the properties of wrought iron. 3.-Explain the meaning of the term steel. 4. In cylinders of metal, the power exerted to resist pressure from within by the different parts varies inversely as the square of the distance of the parts from the axis; prove this. 5.-The angular velocity imparted to a projectile depends upon the length of twist and the muzzle velocity of translation; prove this. 6.-Explain, with diagram, the principal parts of a 64-pdr. Mark III gun. What considerations determine the length of the bore of a gun? 7.-Calculate the angle of deflection corresponding to a speed of 14 knots, when firing at an object distant 1,000 yards, time of flight 2.5 seconds. Does the amount of deflection required to counteract the effect of the wind vary with the distance? Explain your answer. 8.—Find the mean resistance offered by the compressor to the recoil of 9-pdr. 8-cwt 9.-State the conditions which must be satisfied by a good elevating arrangement. 0.-Explain fully how a projectile is propelled from a gun. 11.-Calculate the velocity of a projectile whose weight is 89 lbs. when fired from a 12.-What means have been successively adopted to reduce the pressure in the bore? And how is it that it has been possible to combine increased velocity with a lower maximum pressure? Question set on April 6, and papers given in at 9 a. m. on 5th May. Examine the question of the armament of the unarmored steel corvette Mercury, whose displacement is 3,700 tons. It is supposed that she will be classed as a fifth-rate, that her complement will be 250, and that the weight allotted to armament is 112 tons. GUNNERY LIEUTENANTS. (April 1, 1878.) FIRST PAPER. 1.-Explain the terms, "tenacity," tensile strength," "limit of elasticity" as applied to metals. How are they respectively measured? 2.-Give a description of the manufacture of a steel tube for a heavy gun from the time the ingot leaves the manufacturer's hands until it is ready for the B tube. How is the temperature at which the A tube shall be toughened determined? 3.-Explain the meaning of the term "initial tensions and varying elasticities" as applied to gun construction. How is the principle carried out (a) at Woolwich. (b) by Whitworth. (c) by Palliser. 4.-Enumerate the general properties of wrought iron, and give a description of the process at Woolwich by which it is obtained from obsolete cast-iron material. 5.-What is meant by the term "jump" of a gun? A 9-pounder was laid accurately horizontal for a wooden target 200 feet distant; the height of the level of the axis of the gun was marked on the target; on firing the gun, the shot struck 10 inches above this level. The mean velocity was found to be 1,370 f. s.: Calculate the angle of departure or the "jump" of the gun. 6.-How is the velocity of rotation of a projectile measured Find approximately the number of revolutions per second and also the angular velocity of the projectile of the 7-inch 62-ton gun at the muzzle: Muzzle velocity.. Caliber Twist 1,525 f. s. 7 inches. 1 in 35 calibers. 7.-What means have been adopted to ascertain the pressure, volume of gas, temperature of explosion, and products of combustion, when a charge of powder is exploded in a closed vessel? 8.-What is the actual work realized by 110 lbs. of B. powder, in the 12 inch 35-ton gun; length of bore=16.5 calibers; gravimetric density of powder=1; factor of effect 93.1. Hence find the muzzle velocity of projectile; weight 700 lbs. Total work that gunpowder is capable of realizing per lb. burnt, in foot-tons. Number of volumes of expansion. 9.-What is considered the limiting angle of penetration of our service projectiles? Give approximately the percentage of work lost on impact, owing to the conversion of work into heat in the case of projectiles made of— (a) Wrought iron. (c) Hard-tempered steel. In recent experiments, what material appears to recommend itself most as a metal for projectiles? 10.-State briefly what experiments have been made in England with gun-cotton shells, and with what results? 11.-What method was adopted by the Italian commission in their recent experiments at Spezia, to determine the velocity of shock actually necessary for perforation? If V-velocity of shock on impact with target (as observed) v=velocity of exit after perforation Show that Velocity of shock actually necessary just to perforate=√ √2 — v2° GUNNERY LIEUTENANTS. (April, 1878.) SECOND PAPER. all 1.-Define, with diagrams where necessary, the following terms: "Angle of fire," " gle of descent," "line of sight," "terminal velocity," "high angle fire." 2.-Describe the effect of the resistance of the air combined with the rotation of projectiles of the service form. What theories are advanced to explain the deviation of these projectiles to the right? 3.-Explain, with diagram, the principle of the Boulengs chronograph, and describe how a velocity is obtained with it. What advantage has it over the Bashforth chronograph? 4. An experiment is made with a Bashforth chronograph to ascertain a velocity at one of the screens distant (x) from the muzzle of the gun. The time (t) is end off from the diagram on the cylinder, and also the time of passing the intermediate screens, which are a known distance (h) apart. Show how an equation may be formed, giving the velocity required. 5.-The velocity of the projectile of the experimental 16-in. 80-ton gun was found to be 1,480 f. s. at 400 yards from the muzzle of the gun. Calculate its initial velocity, using Bashforth's tables. 6. Assuming that the second differences of the times between the Bashforth screens. are constant, and that the resistance of the air varies as the (velocity). Prove. Helie's formula: distance from muzzle in feet. c = constant, depending on form, weight, and velocity of shot. 7.-What influence has the form of the base of a shot on the total resistance offered to it by the air? Calculate the resistance offered by the air to the motion of an "ogival-headed. shot." w= weight of projectile ..180 lbs. .1,200 f. s. 7.92 inches. 109.5. Explain how you would test the accuracy of the director and racers. State the advantage of the— (1) Correction plates. (2) Correction tables. (3) Both plates and tables. 9.—Calculate the total horizontal correction to be applied to the director when placed on the starboard side. 10.—The charges of the guns of the Bacchante have been altered from full to battering; why is it necessary to alter the correction tables for her director? 11.-State the advantages of the Dreadnought over the Thunderer, as regards her offensive and defensive strength. Give a diagram of the former's armor plating. NOTE J. QUESTIONS SET AT THE EXAMINATION FOR ADMISSION TO THE FRENCH NAVAL SCHOOL IN 1878. WRITTEN EXAMINATION. FRENCH COMPOSITION. (June 11, 8 to 10 a. m.) Siége de Gergovie par César. Vercingétorix n'ayant pu sauver Avaricum, la capitale des Bituriges, ni empêcher César de passer l'Allier, était allé s'établir à Gergovie, la capitale des Arvernes, pour |