« AnteriorContinuar »
It is said, that the idea of a right-line range is revived, because, towards the close of the seventeenth century, such an idea was very prevalent. Anderson, in the year 1713, published a work, in which he contended, that the first part of the course of a shot was actually in a right line ; that this right-line projection was equal at all angles, and that from the end of it, the trajectory bent into a parabola. However inconsistent with a right-line projection, he was equally strenuous in support of the parabolic system, but it would be difficult, in the present day, to produce many practical gunners who would attempt to maintain either one theory or the other.
That a cannon-shot does not descend in the ratio which the laws of gravity would ascribe to it has been long admitted. J. H. properly observes, that it cannot be adequately accounted for," from the resistance produced by the velocity of the shot's descent," by gravity, and he suggests the idea that it may be attributable to the density of the air by compression, arising from the great velocity with which shot are projected, and the resistance opposed to this dense air by the unyielding material of the earth's surface. It is very possible to imagine that the cause here suggested may influence the trajectory of the shot; if established, it would, in a great measure, account for the difficult and uncommon, though well-attested fact, that persons when standing near some unyielding material, as the mast of a ship, have been killed by what has been termed the wind of a shot ; the shot having passed between them and the unyielding substance.
In addition to the ordinary resistance of the air, it may be considered, that at the velocities with which shot are commonly projected from long guns, a vacuum is created behind the ball, which, as it advances, will occasion a rush of the particles of air at a velocity exceeding 1300 feet; and, when attempting to make any inference from the laws of gravity, it may be well to remember that the theory which supposes that spaces descended are as the squares of the times of descent, also premises that the body descends freely by its own weight, and that the motion commences from a state of rest.' Now it cannot be contended (setting aside the ordinary resistance of the air) that a projectile descends freely by its own weight when urged in any direction with the velocity given to cannon-shot; neither can it be asserted that the motion commenced from a state of rest, since it is certain that the gravitating force commences when the shot possesses the utmost velocity with which it is discharged from the gun. Notwithstanding the great advances made by Mr. Robins and Dr. Hutton in ascertaining the true trajectory of the shot, the truth of the assertion of the Genevese philosophers must still be admitted: “Veræ trajectoriæ descriptionem adeo perplexam esse, ut ex illa vix quidquam ad usus philosophiæ aut mechanicos accommodatum possit deduci.” Dr. Hutton has no doubt gone far to fix the laws of the resistance of the air, and to establish rules by which we may obtain very near approximation as to the velocity and range of shot, but he does not appear to have entered upon the movement of shot horizontally, in connection or combined with the vertical descent by gravitation.
From the practice on Sutton Heath in 1810, under that best of good fellows, Sir George Adam Wood, which was conducted, as to ascertaining the exact range, with more than ordinary care, each ten yards being pegged on an horizontal plane, it appears, by the average, that the point-blank range, or first graze of a 24-pounder, at 0 elevation, is 297 yards. The gun being loaded with the weight of the shot, the initial velocity may be taken at 1610 feet, which, at 297 yards, would be reduced to about 1300; the time of tlight may be considered 1% of a second; the vertical descent by gravity due to which would be 5775 feet : but as the gun was mounted on a garrison carriage, the height of its axis above the plane on which the graze was measured was only 34 feet. Again, the flight of the shot would be, as before observed, very near or of a second, whereas the time corresponding to the vertical descent of 31 feet, is somewhat less than 40. It is very easy to show aided by the discoveries which have been made as to the velocity
of shot, and the resistance of the air, that a shot does not move in a parabola, but the endeavour to trace its true course and to reduce it to fixed rules is beset with very great difficulties ; it has bafiled such men as Newton, Galileo, Bernouilli, Halley, Robins, Euler, Lombard, Hutton. It is not on this account to be despaired of, but ought rather to excite the inquiry and to stimulate the exertions of men of science; and it is in the power of practical men, de nous autres, to aid their endeavours, by affording minute and correct returns of practice, such as, it is to be regretted, do not now exist.
The practice at Sutton Heath, however carefully the ranges might have been determined, may, notwithstanding, be quoted to illustrate the little advantage which can be derived from the data commonly afforded by practice-tables, and may corroborate the opinion formerly offered in this Journal, that the windage and the éprouvette strength of powder, as well as other particulars, should be noted. We have seen, that the point-blank-range of a 24-pounder, charged with ; weight of shot, is 297 yards; now the pointblank of an 18-pounder, also charged with 1 weight of shot is, by the same authority, 385 yards. By theory, and indeed by actual experiment, guns alike charged, that is where the weight of powder for cach gun is in the same ratio as their shot, should have equal velocities : how then is this difference in the range to be accounted for? It may be conjectured, perhaps relied on, that it arose from a difference of windage. The old and new guages for 24-pound shot vary • 109 of an inch; the 18-pounder only .031. The windage of a 24-pounder, with old or new pattern shot, may vary from • 239 to 348; of the 18-pounder, from .218 to 249 only. Unsatisfactory as the information afforded by the practice in question is, in some respects, it tends very powerfully to confirm one principle of considerable importance : heavy shot with less velocities may, with certain elevations, range farther than lighter shot with greater velocity. The following is an abstract of the media of the practice of the 24-pounder and 18-pounder, the charge being one-third the weight of shot; the metal on garrison-carriages, and therefore equally, or nearly so, above the plane on which the ranges were measured; the length of each gun nine feet six inches.
At 5° it may be observed, that the range from each gun was equal; at 10° that of the 24-pounder exceeded more than 200 yards; at 15° more than 300 yards; and at 21°, nearly 400 yards. These results are perfectly accordant with theory, and depend upon the well established rules, that the resistance of the air is as the surfaces or as the squares of the diameters of shot; but the weights of shot (or their power to oppose the resistance of the air) as their cubes.
U, S. JOURN. No. 58, Sept. 1833,
The rules for the practice of artillery are distinguished by horizontal and oblique planes ; practice upon horizontal planes applies to gunnery at sea.
A fluid surface is so nearly horizontal within a circle of l} mile radius, that the following hypothesis may be safely assumed: two bodies floating at sea, and not exceeding the distance of 5000 yards from each other, are in the same horizontal plane ; and if right lines be drawn from one to the other at corresponding heights from their lines of Hoatation, such lines, being parallel to the surface of the water, are in a horizontal position.
The horizon, when visible, is, to the naval gunner, a correct guide by which he can determine the direction of a gun with respect to its elevation above, or depression below, the horizontal line; and it is by the horizon that a ship's artillery may be pointed preparatory to action, so that, when the guns are brought to bear, they will require none, or at most a trilling adjustment.
It is suggested, therefore, that upon approaching an enemy's vessel, to lay the guns by the horizon ; if, for instance, it be intended to engage within the right-line range of the guns, level them by their dispart-sights at the horizon ; for it will be found when they are brought to bear, that they are directed at such parts of the enemy's vessel as are the same height as the guns from the surface of the water; and, consequently, if the two vessels be of like dimensions, the guns on the respective decks will point at those on the corresponding decks of the enemy. Recourse may be had to the horizon should the distance exceed the right-line range; elevation in such case being necessary, the index of the tangent scale must be placed to the height required, and the aim directed to the horizon, as in the case of the right-line range. If the distance at which action is likely to commence cannot be accurately judged, it will be better not to elevate to hit the object at first graze, but try the effect of ricochet.
When the horizon, from darkness or other causes, is not visible, perhaps the following expedient may be resorted to: make, with a piece of chalk or pipe-clay, two marks, exactly on the middle of the base-ring, one nearly on the top, and the other as low down as it can be seen by a person standing about three feet from the side of the gun ; let such person be supplied with à plumb-line, which must be held so that the plumb hangs freely and perpendicularly, the sight being directed by the line to the base-ring: when, by the roll of the ship or movement of bed or quoin, the two marks on the base-ring are brought to coincide with the plumb-line, the axis of the gun will point horizontally. This simple method may be as correct a guide as any that has hitherto been proposed to obtain accuracy of fire under certain circumstances, as when an enemy's ship is hidden by smoke, and her position determined only by the flashes of her guns; in such case the bearing may be known, and the guns can be accurately trained; but there is no other guide for the elevation than that which can be obtained by some pendulous instrument. In using the means here suggested, the horizontal direction of the gun can be ascertained without reference to a detached instrument. The person intrusted with the management of the plumb-line should, at the instant the gun attains a horizontal direction, (the gun being previously trained to the object,) give the word “ fire !" to the man appointed to pull the lock-lanyard or to apply the match,
OBSERVATIONS ON THE HANOVERIAN KNAPSACK.
BY CAPTAIN KINLOCH, 68TH LIGHT INFANTRY, In the United Service Journal for October, 1830, we gave a full and accurate description of the improved knapsack invented by Captain Heise, of the R. H. Jäger Guards. The subject has been lately taken up by Capt. Kinloch, 68th Light Infantry, who, having recently visited Hanover, has had a good opportunity of judging of its advantages,- advantages which have induced him, at his own individual expense, to fit out his own company with these knapsacks. We have therefore much pleasure in laying before our readers the result of that officer's experience; and shall, no doubt, also stand excused for repeating the description and other particulars as furnished us by Captain Kinloch.- Ep.
In the course of a military tour in Germany, last year, I was struck with the appearance of the knapsacks of the Hanoverian infantry; and on learning from the officers that they had found them much superior to those worn by the British troops, -and which they had, until lately, made use of themselves,
- I was induced to bring over one of them to this country, as a pattern worthy of imitation.
This knapsack met with the most unanimous approbation of the Colonel and officers of my regiment, also of many other most distinguished and experienced officers in Dublin; and the knapsacks I found in use appeared so much inferior, after being accustomed for some time to see the Hanoverian, I requested permission of the General commanding-in-chief to allow a trial of the Hanoverian knapsacks to be made by my company of the 68th Light Infantry, which his Lordship was pleased to accede to. His Lordship was further pleased to grant me leave of absence to go to Hanover, and order the knapsacks to be made; and I took this opportunity to institute the most minute and particular inquiries respecting the wear of these knapsacks, of the material of which they are made; and, at Hamburg, made further inquiries as to the supply of that material.
The result of these inquiries was, in every way, most satisfactory, and I am most sanguine in my opinion that the experiment will prove equally so; and that the advantages of the Hanoverian knapsacks being now beyond doubt established, our gallant infantry will be relieved from the oppressive and unsightly pack with which they are at present burdened, and that by this means the health, comfort, and efficiency of the soldiers will be mainly benefited.
The very great inconveniences of our present regulation knapsack are well known to all our officers of infantry ; and although many alterations and improvements have, at different times, been made, and many others suggested, it still possesses many faults; the most, if not all of which may now be obviated by at once adopting the excellent knapsack of the Hanoverians, and such as may be seen in wear by my company in the 68th Light Infantry.
Those persons who carry the knapsacks must be the proper judges of which is the best method of carrying them. Our soldiers must carry theirs according to regulation, however inconvenient they may find it.
In Germany, pedestrianism with knapsacks is practised to a much greater exterit than in this country; every tradesman must, during his apprenticeship, travel a certain distance, and visit certain parts of the country to learn and practise his trade, before he can set up shop and work for himself. These persons cannot afford any means of travelling but on foot, and they carry their goods, clothes, or other necessaries in knapsacks. They can, of course, wear their packs in whatever manner they please; but one mode of carrying them is universally adopted, as being found by long experience to be the easiest for carrying a load any long distance on foot. This mode of
carriage, principally owing to the arrangement of the shoulder-straps, has been closely imitated in the knapsack now adopted by the Hanoverian infantry. It was first proposed by Captain Heise, of the Hanoverian Jäger Guards, an experienced and gallant officer, who has seen much service in the campaigns during the Peninsular war, and those of 1814 and 1815, in the Ist Light Battalion of the King's German Legion, to whom I am much indebted for the interest he has taken in my introducing this knapsack into the British army; and he has rendered me the greatest assistance in superintending the manufacture of the knapsacks for my company, and afforded me every information on the subject. This knapsack was submitted to a board of officers at Hanover, appointed to fix upon a new regulation pattern for the infantry, and it was approved by the board, after having been tried for some time by experienced non-commissioned officers and privates, who unanimously declared its very great superiority to the old regulation knapsack, the same as that still worn by our infantry; and eight years' experience has realized, beyond their most sanguine expectations, all the advantages that were expected from it.
I cannot better describe the peculiar merits of this knapsack, and the details of its construction, material, &c., than by quoting principally from a pamphlet written by Captain Heise, and addressed to “ the AdjutantGeneral of the British Army," in 1828, when he proposed a knapsack to the notice of the Commander-in-Chief, but a new regulation pattern having at that time been fixed upon, it was not tried in our service. The pattern which was then chosen, however, not having answered all that was expected from it, being still very faulty, and the Hanoverian knapsack being now further improved, from some alterations suggested by experience, and adopted with advantage, I trust that its superiority will entitle it to an early and universal adoption in the British army, where an improved knapsack is so much required and looked for by the infantry.
“ Although experience has fully supported the judgment of the board, and the pattern might simply be referred to in proof of its good qualities, I shall proceed to detail the reasons which influenced me to suggest so considerable an alteration in the material and construction; and I trust you will feel satisfied that the design has not been founded upon any crude theory, or untenable hypothesis, but upon principles deduced from practice, and facts established by experience.
“ The fundamental properties of a good knapsack appear to me to be three in number :
1st, The exterior construction. • 2d, The interior construction. “ 3d, The material.
“ 1st. Of the exterior construction. The shoulder-straps form the most important part: these should be such as to enable the soldier to carry his knapsack without impediment to his action, or injury to his health.
“ 2d. The interior construction should be such as to enable the soldier to pack and unpack his knapsack with the greatest ease, and in the least possible time.
3d. The material ought to combine the qualities of durability on service, and imperviousness to wet and damp, to the highest possible degree.
“ The shoulder-straps are fastened to the upper part of the knapsack in such a manner as to prevent it moving from its proper position, either by lowering itself or hanging back, at the same time their construction renders the breast-strup superfluous,--an effect which may be considered as the most important advantage of this construction.
• In order to ascertain the comparative facility of carriage of the knapsack proposed by me, and those already in use, the board of otticers at Hanover, to whom the investigation was entrusted, directed a detachment, consisting