R-Find the mean resistance offered by the compressor to the recoil of 9-pdr. 8-ewt: gull1. When the recoil is 3 feet. 2. When the recoil is 1 inch. Given the weight of projectile. 99 lbs. Initial velocity of ditto... 1, 380 feet. Weight of carriage... 275 lbs. 9.-State the conditions which must be satisfied by a good elevating arrangement. 0.-Explain fully low a projectile is propelled froin a gim. 11.-Calculate the velocity of a projectile whose weight is 89 lbs. when fired from a 64-pr. M. L. R. gin: Given the caliber... 6.3 inches. Length of bore. 15. 5 calibers. C!:arge ... 12 lbs. Gravimetric density 1. Factor of effect 76. Number of rolumes of expansion. Total work in foot tons that the powder is capable of realizing per Ib. buned. 8.3333.. 101.00 9. 0909 103. 82 10.0000. 106.87 11.1111 110.18 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 fift h-rate, that her complement will be 250, and that the weight allotted to armament is 112 tons. GUYNERY LIEL'TEXAXTS. (April 1, 1878.) First P'APER. 1.-Explain the ter "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 tonghened 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. (a) by Rodman. -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. 1.-What is meant by the term "jump" of a gun? 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 inarked 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 gmn. 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 6f-ton gun at the muzzle : Muzzle velocity. 1,525 f. s. Caliber 7 inches. Twist 1 in 35 calibers. 7.-What means have been adopted to ascertain the pressure, voluine of gas, tem perature 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 Nunber of volumes of expansion. is capable of realizing per lb. burnt, in foot-tons. 6. 2500 91. 45 6. 6667 93. 64 7. 1429 95.94 7.6923 98. 39 8.3333 100.00 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 experi ments at Spezia, to determine the velocity of shock actually necessary for per foration ? 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=V V2 — vào GUNNERY LIEUTENANTS. (April, 1678.) SECOND PAPER. 1.-Define, with diagrams where necessary, the following terms: “Apgle of fire," “ an 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 pro jectiles 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 (l) is end off from the diagram on the cylinder, and also the time of passing the interme diate screens, which are a known distance (1) 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. 8. at 400 yards from the muzzle of the gun, Calculate its initial 1,700 lbs. 15.92 inches. 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: V 1+cVx When v= velocity at any point. V=muzzle velocity. = 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. v = velocity .. .1,200 f. s. d= diamemter ot' shot .7.92 inches. k for that velocity ... 109.5. 8.-In what plane should the racers be laid ? Explain how you would test the accuracy of the director and racers. (1) Correction plates. (3) Both plates and tables. 9.-Calculate the total horizontal correction to be applied to the director when placed. on the starboard side. d= distance abaft center gun 60 feet. R=range.... 800 yards. t= time of flight 2 seconds. 8=speed ..... 10 knots. 0 permanent angle of deflection...... 1° 10'. angle of elevation..... 1° 15'. Why will this table be inaccurate for the port director? 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. NO TE J. QUESTIONS SET AT THE EXAMINATION FOR ADMISSION TO THE FRENCH NAVAL SCHOOL IN 1878. WRITTEN EXAMINATION. Siege de Gergovie par César. laisser aux conjurés le temps de se réunir et de s'organiser avant de livrer une bataille décisive aux envahisseurs de la Gaule. Gergovie était une place très-forte, assise sur une hauteur et entouréo presque de tous côtés d'une ceinture de montagnes dont elle était séparée par une plaine étroite. Vercingétorix avait rassemblé sur ce point des forces nombreuses qui, couronnant toutes les hauteurs, dominaient entièrement la plaine. César enleva un des plateaux qui faisaient face à la ville, et lui livra plusieurs attaques, mais ne pouvant engager l'ememi à une bataille et impatient d'obtenir un succès pour prévenir la défection de ses alliés, il tenta une surprise et fit donuer un assaut; illaisse entendre dans ses Commentaires qu'il éprova un échec considérable. Snétone avoue sans détour que les Romains furent repoussés avec des pertes énormes. (June 11, 1 p. m. to 2.30 p. m.) C:esar, ut Brundisium venit, contionatus apud milites, quoniam prope ad finem laborum ac periculorum esset perventum, irquo animo mancipia atque impedimenta in Italia relinquerent, ipsi expediti naves conscenderent, quo maior numerus militum posset imponi, omniaque ex victoria et ex sua liberalitate sperarent, conclamantibus omnibus, imperaret, quod vellet, quodcumque imperavisset, se æquo animo esse facturos; pridie nonas ianuarias naves solvit, impositis, ut supra demonstratum est, legionibus septem. Postridie terram attigit Cerauniorum. Saxa inter et alia loca periculosa quietam nactus stationem, et portus omnes timens, quos teneri ab adversariis arbitrabatur, ad eum locum, qui appellatur Palæste, omnibus navibus ad unam incolumibus milites exposuit.—(Caesar, de bello civili, lib. iii, cap. 6.) ENGLISH VERSION. (June 11, 3.15 p. m. to 4.15 p. m.) On voyait la côte et le sinistre cap de Trafalgar qui a donné son nom à la bataille. Un vent dangereux commençait à se lever, la nuit à devenir sombre, et les vaisseaux anglais, manquvrant difficilement à cause de leurs avaries, étaient obligés de remorquer ou d'escorter dix-sept vaisseaux prisonniers. Bientôt le vent acquit plus de violence, et aux horreurs d'une sanglante bataille succédèrent les horreurs d'une affreuse tempête; comme si le ciel ent voulu punir les deux nations les plus civilisées du globe, les plus dignes de le dominer par leur union, des fureurs auxquelles elles venaient de se livrer. ARITHMETIC AND GEOMETRY. (June 12, 8 a. m. to 11 a, m.) 1.-State and explain the theory of the periodical fractions and apply to air and Mr. 2.-Prove that periodic fractions, 'derived from irreducible fractions of the same de nominator, have the same number of figures in a period. Take as an example Tir and is 3.—Prove that the expression for the volume generated by a circular segment is | DH; D being the chord and I its projection upon the diameter. As an application inscribe a right cone in a sphere such that its volume shall be one-half of the spherical segment in which it is inscribed. DESCRIPTIVE GEOMETRY. (June 12, 1 to 2.30 p. m.) A point situated in the first dihedral angle is situated 5 cm. from the horizontal plane and 44 cm. from the vertical plane. This point is the center of a regular hexagon, whose plane is parallel to the hori'zontal plane, and one of whose sides, parallel to the vertical plane, is 3 cm. in length: This hexagon is the common base of two regular pyramids, of which one has its vertex in the horizontal plane, and the vertex of the other is situated at a distance of 7 cm. from this plane. It is required to construct the shadow of this pyramid upon the planes of projection, knowing that there exists in the first dihedral angle a source of light which sends its rays parallel to a right line, making an angle of 190 with the horizontal plane and 33° with the vertical plane. ALGEBRA AND TRIGONOMETRY. (June 13, 8 to 11 a, m.) 1. Find the maxima and minima values of the function 2r? – 88 + 8 y= x2 – 5x +4 Examine the variation of this function for all values of x from – o to + , and trace the corresponding curve. 2. Resolve the triangle ABC, having given a=3875.475 m. 6143.877 m. Deterinine the surface in hectares. ORAL EXAMINATIONS.—PARIS. NOTE.—Three sets of questions have been selected from a large number given at the Paris examination. They have been taken at random, and they are fair examples of the questions at all the centers of examination. EXAMIXATION OF CANDIDATE A. 1.-ARITHMETIC. 1.-Let A=ap he c', a number of which, a, b, and c, are the prime factors. Find the number of divisors of A. 2.-In how many ways can the number A be decomposed into two factors which are prime to each other ? 3.-Explain the rule of simple interest. 2.-GEOMETRY OF SOLID BODIES. 4.-Give the theory of symmetrical figures. 5.-Determine the volume generated by a segment of a circle which revolves about an axis passing throngh the center of the circle. 6.—The continuous trace of an ellipse. The length of the radii vectores passing through the extremity of the shorter axis. Draw a tangent to the ellipse (1) through a point on the curve (2) through an exterior point. 3.-ALGEBRA. 9-1 7.-Give the sum of the terms of a geometrical progression. 8.-What does the formula 8 = 19—a become when q becomes equal to 1? 9.-Give the formula for computing interest. 10.- How long is it necessary that a capital, A, should remain at interest, at a given rate, in order to become C? 11.- Investigate the sum of the squares of two numbers, x and y, whose sum is a con stant. 12.-Define a maximum and a minimum. |