It may be remarked that the top-sight in general use in the navy, is raised above the axis of the piece somewhere about a foot, so that strictly speaking, the centre of the shot should strike a foot below the point aimed at. The sight might easily be adopted to correct this error by computing the angle subtended by one foot, (supposing that to be the space betwixt the gun's axis and the sight,) at various distances, but it may be safely neglected in practice. Indeed, for short distances, it is provided for, by the adoption of the alteration mentioned above. In number II. III. of the "Annales Maritimes for 1831," M. Roche has investigated the subject of pointing naval ordnance, and founding his calculations on experiments inade at Brest in 1824, with a French 30-pounder gun, (equivalent to about thirty-two and a half English,) has given various tables of ranges, which I shall transcribe. The charges used were one-third and one-fourth of the weight of the shot, and M. Roche remarks, that the increase of range due to the larger charge, was about one-thirty-second part of the whole. The initial velocity which M. Roche obtains is 1230 feet per second: now the usual velocity with which shot are discharged in our practice from long guns, is generally between 1500 or 1600 feet per second; consequently, the following ranges may be considered as erring in defect for the corresponding elevations. I have, however, thought it better not to increase them, as in the first place the ratio of the range to the initial velocity is not correctly known;* and secondly, as I conceived it to be the safer side to err on, owing to the great probability of using in practice gunpowder which is deteriorated by keeping, or shot whose windage is increased from the same cause. The French measures have been reduced to English, assuming the French foot to be equal to 1.0658 English. Table II. gives various angles of elevation and the corresponding ranges in yards. TABLE II. Showing angles of elevation and the corresponding ranges in yards; the gun being 4.25 yards above the horizontal plane on which the ranges are measured. -1° 0′-0°40′ -0°20′ 0° 0′ 0° 20′ 0° 40′ 1° 0′ 1° 20′ 1° 40′ 2° 0′ 2° 20′ 2° 40′ 3° 0′ 176-1 215-6 268-3 338-8 425-3 525-3 633-4 746-0 859-3 971-1 1080-41186-61288-9 The negative sign indicates depression. Table III. is formed from Table II. by simple proportion, and gives the elevations corresponding to various distances. TABLE III. 200 300 400 500 600 700 800 900 1000 1100 1200 1300 -0° 48′ -0° 11' +0° 14' 0°35' 0°54' 1°12′ 1°29′ 1°47 20 62°24′ 2°42′ 3° 2′ 14/0°35' Tables II. and III. are adapted to throw a shot to strike the enemy's Assuming the ranges to vary as the square roots of the initial velocities, those given in this paper should be increased by about their eighth part. hull at the water-line, which is assumed to be nearly thirteen feet below the gun; the following table shows the requisite elevation when the point to be struck is in the same horizontal plane as the gun. TABLE IV. Showing the angles of elevation required to strike a mark situated in the same horizontal plane as the gun. 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 0° 11° 23′0° 35'0 47 1 1 10 15 1° 30′ 1° 46′ 2° 2′ 2° 18′2° 34′ 2° 52′ 3° 9′ The three foregoing tables can only be used when we possess some means of measuring the angle of elevation, such as a pendulum, or by our knowing the point in the enemy's hull, which is at the same height from the water as the gun, and pointing at it after having adjusted the sight to the proper angle. To modify them so that they may be used when we possess no such means, we must calculate the angle subtended by the height of the gun at the given distance, and add it to the tabulated angle from Tables II. and III. then adjusting the sight to this newly obtained angle, aim must be taken directly at the water-line, when it is obvious that the axis of the piece will be at the proper elevation. These corrections are in the following table. TABLE V. Showing the corrections to be added to the angles from Table III. 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1°13' 0°49' 0°36' 0029' 0°24' 0°21′ 0°18′ | 0°16′ 0°15' 0°13′ 0°12′ 0°11'] Thus, for example, if it be wished to strike the water-line of a ship distant 800 yards, the gun being placed 4-25 yards above the water, we must seek in Table III. for the proper elevation which we find to be 1° 29'. In Table V. we find the corresponding correction to be 0° 18′. Their sum equalling 1° 47′ is the angle which must be adjusted on the sight, to enable us to direct the gun properly by pointing at the water-line. In the same manner, we find that to strike a point the same height as the gun, the distance being 800 yards, we must adjust the sight to 1° 46′ 0° 18' 2° 4′ and then take aim also at the water-line. It will be seen that the angle from Table III. corrected is nearly identical with that from Table IV. whence we may conclude that the latter table will serve for the purpose of pointing to hit any object, situated thirteen feet below or above the gun; the error committed by using it being very far within the uncertainty of practice. Should the guns be only fitted with a fixed sight, it will be useful, in These tables are adapted for long guns. From some late practice with a 32-pounder carronade, charge one-twelfth the weight of the shot, its ranges reckoned on the same horizontal plane as the gun, appear to be nearly as follows: deed necessary, to calculate tables which are known by the rather uncouth name of " Tangent Practice Tables," similar to those given by Churruca, and more lately by Sir Howard Douglas. Putting e for the elevation from Table IV., e for the fixed elevation of the " point-blank sight," d for the distance, and h for the height of the gun above the water, then the height above the enemy's water-line of the point to be aimed at = x = d. tan. (e—e') + h. Aiming, therefore, at a point in one of the masts (the dimensions of which may be estimated pretty accurately) which is a feet above the water-line, the shot should strike h feet above that line. Should it be wished to strike higher or lower than that point by a few feet, the aim must be altered by nearly the same quantity. There is an additional advantage (already noticed by Sir Howard Douglas) in aiming by the enemy's masts, because even if the shot strike above or below the intended aim, the chance of taking effect is of course increased. Table VI. shows the values of x, in feet, the fixed sight being at an elevation of 0° 20′. TABLE VI. Showing the heights above the water-line to be aimed at, sight fixed at 0° 20′. 200 300 400 500 600 700 800 900 1000 1100 1200 1300 13-3 16-7 22-230 6 41 5 55-572-893-1 115-8141-4 172-0 204-6 From Table I. we learnt that the ratio of the depressions of round to double-headed shot was as 2: 3. Now, from the best published experiments, the range of the former to the latter is about as 3:2. Hence it appears the depressions are inversely as the ranges. In Following the same analogy, it is not improbable that the depression of grape-shot (by which is meant the depression of the centre of effect) is double that of round-shot, the ranges being nearly as 1 : 2. creasing, therefore, the values of x-h in these ratios, we may calculate the elevations for double-headed and grape-shot for various distances, by reversing the process given above. Therefore putting b equal to the increased value of x-h; tan. (e—e)=√ TABLE VII. b No use, however, can be made of these or any other tables of a like nature, unless we are provided with the means of measuring distances * Instruction sur le Pointage de l'Artillerie, &c. Treatise on Naval Gunnery, First Edition, p. 231. accurately at sea. h If the dimensions are known of the masts of the vessel, whose distance is required, the process usually employed is simple. Measure the angle a subtended by any known height h, then Distance= Many persons when measuring this angle bring down the reflected image to the water-line, and not to that part of the vessel corresponding in height with their own eye; and although this error needs only mentioning to be acknowledged, the fact that it is not unfrequently committed may serve as an apology for noticing it. tan. a It often happens that the dimensions of the distant vessel are unknown, and this inconvenience suggested the following method which is believed to be new. Measure the angle subtended by the space betwixt the horizon and the water line of the distant vessel; calling this angle a and the dip of the horizon d, it is plain that a+ is the angle subtended at the distant vessel by the height of the observer's eye, which is known. h Calling it h, Distance = A small correction is due for tan. (a + d) the spherical form of the earth, which for this purpose may be safely disregarded. It must be recollected that all the foregoing tables of ranges depend on the accuracy of the Brest experiments, and also, that as they were made with a different species of ordnance than is in use in the British service the results are not immediately applicable to our practice; the ranges too, although given for angles of elevations which are tabulated to minutes, have no pretensions to that degree of accuracy. It is often remarked, when attempts are made to introduce improvements in Naval Gunnery, that it is quite useless refining too much, as the errors arising from the ship's motion are so great as to render all others trifling in comparison. To reply to this we should recollect that we can only reach perfection by distinguishing between unavoidable inaccuracies and the errors arising from imperfect knowledge of the subject. In conclusion, I shall take leave to remark on the vast importance of the foregoing subject in a national point of view, and to venture to express a hope that before long, experiments may be instituted on a larger scale than heretofore, which may afford to naval officers some data on which they may regulate the practice of the various natures of guns with which men-of-war are armed. They themselves often have it in their power to make trials, which if recorded faithfully, with all the attendant circumstances (even those which may appear at the moment to have little or no connexion with the subject) might add materially to our stock of knowledge, the more so as these experiments would be made under circumstances similar to those in which their ships would be fought. D. REVIEWS AND CRITICAL NOTICES. COLONEL NAPIER'S HISTORY OF THE WAR IN THE PENINSULAVOL. III. * IN the notices which we have been heretofore called upon to take of Colonel Napier's History of the Peninsular War, we have endeavoured, as far as possible, to divest ourselves of every thing like partiality, favour, or affection, and to speak of the performance in such terms as its merits alone seemed to require. Upon these grounds, and upon these grounds only, we have pronounced it to be by far the ablest and most eloquent account that has yet been given of any portion of the great contest. Clear in its details, animated in its descriptions, and abounding with marks of deep (we wish that we could add always of) sober thought, no person, however unaccustomed to unravel the intricacies of military history, can find himself at a loss in following its narrative; while the professional reader discovers at almost every page some great lesson recorded, from the study of which he rises, if not a better," certainly " a wiser man.' This is very high praise we are aware, so high, indeed, that we could scarcely name a second work of the kind on which we should be disposed to bestow it,-yet it is fully and richly earned by Colonel Napier. We do not say that he is the best narrative-writer of his day-we do not profess to go along with him in all his arguments, nor even to assent to the whole of the postulates on which his reasoning is founded. We do not acquit him of faults either in style or arrangement, for the former, though vigorous and clear, is not wholly devoid of affectation, nor is the latter always such as we imagine that it might have been, but we repeat, that take it for all in all, the History of the War in the Peninsula stands, and deserves to stand, at the head of all similar productions which have yet appeared, either in England or elsewhere. No doubt other accounts of the Peninsular war will be given,-some of them, (one of them at least,) advance still loftier pretensions to public favour, but we are greatly deceived if any other shall succeed in consigning Colonel Napier's elaborate volumes to the oblivion which must necessarily overtake the great mass of similar performances. Entertaining an opinion so exalted of Colonel Napier's work, and as a necessary consequence of the genius and talents of its author, it is exceedingly painful to us that we are compelled to notice in the volume now under review, proofs more and more glaring of the baneful influence of party and political prejudice over minds the most honourable and the most cultivated. If there lives the man whom we could have expected to triumph over such feelings, that man is Colonel Napier. Unconnected, as far as we know, by family or personal ties with any political faction whatever, and educated in a school from which the curse of faction is for the most part shut out,well read, moreover, in classic lore, and of course not unaccustomed to weigh the effects of party spirit both in public and in private, we cannot so much as divine a cause why he should descend from the proud eminence of impartiality, and surrender up a judgment naturally sound and clear, to the guidance of a principle for which we are at a loss to devise an appropriate name. It is to no purpose that Colonel Napier may assure us of his intention to advance no statement which shall not be fully borne out by facts. We do not doubt this-we are sure that he never wrote a line or uttered a sentence which he himself did not believe to be correct. We are convinced • History of the War in the Peninsula and in the South of France, from the year 1807 to the year 1814. By W. F. P. Napier, C.B. Colonel H. P. 43rd regi. ment, and Member of the Royal Swedish Academy of Military Sciences.-Vol, iii. |