ON our preceding page is a drawing of a Chain Messenger, invented by Messrs. Gordon and Co. London, which has lately been tried with complete success in the Navy, East India Service, &c. The following short description will render the subject quite clear; we must refer to the inventors for detailed particulars. At the lower part of the capstan, a wheel (B) is firmly fixed, the cogs of which take into each link of the chain messenger for about half the circumference of the wheel, thus having a very powerful hold; and while, by an ingenious method of shaping the links, the cogs come into action in the most advantageous manner, the chain messenger is at the same time prevented from twisting round. Two rollers (CC) support the slack part of the messenger before the nippers, and upon these it is carried round the fore part of the deck: these rollers being moveable in a slide on the block (D), allow the messenger to be brought to the required degree of tension. It is unshackled after use in the same manner as chain cables. E. Shows the manger on the new plan. F. The hawse holes. G. H. Shows the cable connected as usual to the Messenger. I. K. The main-mast. L. The main hatchway. M. N. Shows the mode of shackling the messenger. The advantages of this messenger consist in its convenience for stowage, both as it respects room and time; its keeping the cable tiers always clear for use; the rope messenger in ships-of-war being stowed in the heart of one bower tier, and the spare one in the heart of the other, both of which must, therefore, be hauled on deck before the cables are ready for running. It requires no shifting; after one anchor is hove up, the other may be immediately brought to. It requires no holding on, or lighting forward, nor any lighting round the manger; thus placing forty or fifty men and boys in a 74 at disposal for other duties. This point will prove a great convenience to the East India Service, who have full work for all their crew. The troublesome and dangerous operation of surging every three or four minutes while heaving-in, is entirely avoided; in fact, the official reports invariably state that no stop takes place from first to last, if the capstan is sufficiently manned. In addition to this it is to be noted, that by hanging the veering cable, in unmooring, to the chain messenger, it rouses it up the hatchway, and carries it entirely along the deck; by which the labour of thirty more men is saved in a line-of-battle ship. In surging for catting, the cable only is stoppered before all, and it is then surged through the turns of the stopper. When this messenger is applied to their improved patent capstan, this department of nautical mechanism seems complete. Messrs. Gordon and Co. have given in a Pamphlet all the details, accompanied by Official Reports to the Admiralty, &c. These Messengers have been lately fitted to the Alfred, Barham, and Hebé. A POPULAR VIEW OF FORTIFICATION AND GUNNERY. NO. IX. Retrenched Camps.-There are few fortresses capable of receiving within their walls 20,000 or 30,000 men; indeed, such places would require an enormous expense, both in their construction and in their repairs, stores and garrison. Vauban proposed to make fortresses of a moderate capacity, fit to serve as a shelter for an army or some divisions of an army, to aid in the general arrangements of a campaign, by forming a retrenched camp under the guns of the place. An enemy would not hazard passing such a retrenched army as 20,000 or 30,000 men, that would be on the alert to cut off his communications; and a single corps of observation would not suffice to hold such a garrison in check. This kind of fortification, as being between permanent and field, has been called mixed fortification. Fig. 70 is Vauban's idea of a retrenched camp. Fig. 70. B Its general outline ABCD forms as much as possible straight lines, in order that the salient points, which are most likely to be first attacked, may be reduced to the fewest possible in number. This tracing rests its base on the fortress; the profile should be bold; the parapets having at least nine feet and a half of height, and the ditches sixteen feet of depth, surrounded by a glacis, to cover part of the parapet and to heighten the counterscarp; every precaution usually taken to render U. S. JOURN. No. 33. AUGUST 1831. 2 L field-works secure from a coup-de-main should be adopted to strengthen these works. The salient points B and C most subject to attack are strengthened by retrenchments ee; in these most exposed parts the bastion tracing is used as being the strongest; but a more simple trace will suffice under the guns of the place. Frederick the Great shut himself up under the cannon of Seweidnitz with an army of 40,000 men, in a retrenched camp, constructed, not in a continued line of parapet, as in Fig. 72, but by lunettes at intervals; the angles of the general trace being defended by redoubts; so that he could freely move out when necessary to take the offensive. These lines were constructed in four or five days, and within them he defied the Allies triple his number. Marshal Soult had an army of 35,000 men in 1814, which he most ably entrenched in a position around Toulouse. Colonel Jones says, "This city presented many peculiar and great local advantages in furtherance of his labours, being surrounded by a defensible wall, three fourths of which are covered by the canal Royal du Midi, or by the Garonne, an impassable obstacle. Therefore to give that considerable portion of the circumference the strength of a moderate fortress, it was only necessary securely to cover the communications over the canal; and, being zealously aided by the labour of the inhabitants, he quickly effected this by fortifying various buildings and constructing field works of a stronger profile than usual. All direct approach to the remaining fourth of the enceinte not covered by the rivers, was interdicted by the state of the cross roads, being also flanked by a range of bold hills, the summit of which the French had strongly occupied by five redoubts, and had formed various lines of entrenchment in support of them, and to connect the flanks of the ground with the defences of the town. At the foot of the heights runs the river Ers, all the bridges over which out of the fire of the works were destroyed. Such was the advantageous position in which Soult decided to try the fate of arms. Yet it was carried by the Allied army under the Duke of Wellington on the 10th of April 1814. But as the operations of the day consisted entirely in the attack of formidable retrenchments, the loss of the victors was very considerable; probably exceeding that of the vanquished: above 4500 Portuguese and British having been killed and wounded, and more than half that number of Spaniards."-See Jones's War in Spain, page 382, plate 4. The same able Commander (Soult) has given us another instance of his opinion of the value of retrenched camps, in the works of this nature that he ordered to be constructed at Bayonne, from whence he was forced by the Duke of Wellington to retire to the position we have just mentioned at Toulouse. We still quote the words of our military historian Jones (vol. ii. of his Sieges): in speaking of Bayonne, he says "Soult had caused his troops to labour incessantly throughout the winter in strengthening and adding to the capacity of this frontier bulwark, and had formed an advanced line or entrenched camp nearly parallel to the ramparts, at 500 or 600 yards in their front. This advanced line of works being well supported by inundations and other natural obstacles, was of great strength, and covered sufficient space to enable the garrison to form unseen and unexpectedly attack with their whole force the works of the besieger, necessarily divided by the Nive, and may be considered to have given Bayonne on the left of the Adour, the strength of a first-rate fortress.' Much has been said and written in favour of, and against, retrenched camps; it is not a question for us to decide, whether a body of 20 or 30,000 men could be more usefully employed in active operation in the field than resting under the protection of the guns of a fortress, and occupying a strong position there; we speak only of corps d'armée driven to the necessity of such a measure by the circumstances of the campaign; when assuredly we may say with Napoleon, that although "There are military men who ask of what use are fortresses, retrenched camps, and the art of the engineer, we would ask in our turn, how is it possible to manoeuvre with inferior, or even with equal forces, without the aid of positions, of fortifications and all the supplementary means of the art ?"* Besides, should it be advisable to evacuate a retrenched camp, the original strength of the fortress is not at all diminished thereby. Even a grand army composed of the vast numbers that have taken the field in our last war, might benefit by the support of a fortress on which to rest one wing, as in Fig. 71, Fig. 71. while the most efficient divisions of the army are placed on the other wing, advanced towards the side susceptible of attack. Had the confederate army that advanced from the Apennines in 1512, to relieve Ravenna along the right bank of the Ronco, adopted this self-evident proceeding, the result of that campaign might have been very different. Ravenna stands on the left bank of the Ronco, at three miles distance from the sea, on which side the French besieged it, while it was gallantly defended by a Spanish garrison. The confederates advanced by the right bank, and it might naturally be assumed that they would have passed by the besieging army on the opposite side of the river, entered the city, and supported by it, formed an entrenched camp in a formidable position; instead of which they halted short of Ravenna, on arriving within sight of the French army, covered their front by a trench, and resting their left flank on the Ronco, offered battle; which the French, in their desperate circumstances, eagerly accepted under their ardent young leader of twenty-two years of age, Gaston de Foix, and crossing the Ronco in presence of the confederates, attacked and defeated them. In speaking of points of support in the environs of fortresses to favour the manœuvres of an army upon the defensive, and between which it can change front without danger to meet the enemy on whichever side he may present himself; Gen. Rogniat in his work entitled "Considerations on the Art of War," says― "I see no better manner of fulfilling these conditions than that of esta Conversations de Napoleon, par Montholon. + See Colloquies with Folard, U. S. Journal for October 1830. D 口 blishing four little forts around each place, forming a great square, in the centre of which is the fortress as in Fig. 72. Fig. 72. These forts should be established on the summits of the most advantageous heights, at about 2400 or 3000 yards from the works of the place, and about 6000 yards from each other; the space comprised between two forts would form a field of battle capable of receiving from 50,000 to 100,000 men, and might be looked upon as impregnable; the forts, armed with heavy guns, would perfectly support the wings, and the centre could be strengthened by field-works constructed at the moment of need. Thus, the four forts circumscribing each fortress, would form all around a vast retrenched camp, presenting four fronts or four different fields of battle, so that face could be made against the enemy on whatever side he presented himself. The ordinary guard of this retrenched camp could be reduced to that necessary for the four redoubts, which could not be more than 800 men; the fortress itself serving as a depôt for the subsistence and re-organization of the army. It is easy to vary the disposition of fortification according to the nature of the site of each fortress, to adapt it to the ground, and to profit by natural positions." The good defence of Dantzig in 1813 by the French army under Gen. Rapp, shows the advantages arising from the foregoing dispositions; the following is an extract from an interesting relation of this siege by Capt. d'Artois. The mode of exterior defence presented many advantages. It secured D |