lines between the Sture and the Doire, and to arm them with 40 pieces of cannon; but these lines were forced on the 7th of Sept. at daybreak, by Eugene's furious assault (E E E, Fig. 74), aided by a sortie from the garrison. The French army was thrown into great disorder: the siege was raised, the magazines burned, the artillery spiked and abandoned, and the army retreated by Montcallier, after a loss of 8000 men. By this enterprise, Eugene made himself master of the whole of Italy.

The Seven Years' war affords some curious instances of blockade and investment. In our days it is difficult to credit how Frederick the Great should have attempted, and succeeded in, blockading Prague in 1757, with an army of 50,000 men, in which was shut up an Austrian army, under Prince Charles, of a like number of good troops, with a considerable train of artillery. This investment lasted six weeks. Besides great detachments, the Prussians formed a chain of posts of many leagues, divided into two parts by the river Moldau. One bridge above and one below Prague, were the only communications between the Prussian wings, so that in issuing from Prague, the Austrian army would have had but one wing to fight. Even when one of these bridges was swept away by the current, the Austrian leader allowed the opportunity to pass unimproved.

As another instance of Frederick's temerity in this respect, he attempted, in the campaign of 1760, to besiege Dresden, (which was garrisoned by 16,000 men,) in presence of an Austrian army of succour superior to his own. Again, in 1762, he besieged Schweidnitz with 14,000 men; it was defended by 11,000 Austrians; while Marshal Daun, with an Austrian army of 90,000 men, remained a spectator of the siege, and appeared to be there more to cover than to prevent it and overwhelm the Prussians, which he might easily have done. The slow and feeble operations of the Austrians during this Seven Years' war, led Frederick to hazard rash enterprises of this kind, which would have ruined him with a more active and bold enemy.

In 1709, when Mons was invested by Prince Eugene and the Duke of Marlborough, they preferred going out with the investing corps to meet the French army of succour to remaining in their lines, which led to the battle of Malplaquet, in which the French were defeated.

In 1793, the combined army, under the orders of the King of Prussia, that sat down before Mayence, exceeded 100,000 men.

The same year, the combined armies of England and Austria invested Valenciennes with 120,000 men. Prince Cobourg undertook the siege of Quesnoi with 60,000 men. The Duke of York could not invest Dunkirk and Bergues with 50,000.

In 1794, Valenciennes and Quesnoi were shut up and besieged by a corps of the French army, amounting to 20,000 men; but it had only to act against the garrisons. The same year the French besieged Charleroi, with an army of 80,000, and at the moment of the surrender of the place, an army of succour of 100,000 men attacked the French line of circumvallation, (the general arrangement of

The mining operations of this siege have already been detailed in the Sixth Number of these articles, published in our Journal for December 1830.

which was entrenched positions, camps, and quarters,) and in which they repulsed the assailants with great loss.

In 1796, Buonaparte invested Mantua with 20,000 men, but the siege was undertaken with only 9 or 10,000. The Austrians advanced on all sides to raise the siege, and to envelope the French army. Buonaparte, instead of shutting himself up in lines, where he would have had to sustain attacks from superior forces, preferred raising the siege, and, abandoning his artillery, proceeded to attack the divided forces of the veteran Austrian Commander, Wurmser, the splendid results of which are well known. These few foregoing examples have been quoted, in order to give some idea of the complex and difficult situation in which a commander is often placed when a siege becomes necessary; having to attend to the strict investment of the place, to the siege operations being carried on vigorously and efficiently, as well as to the watching and baffling of any attempt to relieve the place by an army of succour. Judging from the facts that military history affords, it seems to be dangerous for "an investing or covering corps to wait in its lines for an attack from an army of succour; and it is found that the most talented commanders have been forced from them. Yet it cannot be denied, that the construction of the lines of circumvallation in the wars of the last century, (when they were most in fashion,) were extremely vicious, having usually an immense developement in a circular form, where weak points were sure to be found; and when forced in any one point, the other parts were taken in flank and in rear; and all this taking place so immediately before the place, renders it difficult to raise the siege by a well-ordered retreat, consequently the siege stores and materiel can scarcely fail to fall into the hands of a garrison of moderate activity.

It has been laid down as a maxim, that it is time enough to think of fortified places when the great question has been decided with the armies that cover them; that the best means of covering a siege is to act offensively, and to give to the enemy's line of operations, the greatest possible depth, in order that he may have a considerable space of country to pass over to save the place.

From the above statements we may safely look upon the able arrangement for the investment and blockade of Pamplona, under our own great Captain, Wellington, (detailed in this article,) as a proceeding much superior to the old method of surrounding a place, by lengthened lines of circumvallation and countervallation. In the latter case, Vauban estimated the period necessary for the construction of such lines to be nine days, averaging, even in a small place, a developement of thirty miles; the mean breadth of the ditches being 12 feet, and the mean depth 7 feet 6 inches; and that a man can dig and remove 540 cubic feet of earth, which forms one toise of running entrenchment, in seven days. Thus, about 18,000 men would be constantly employed day and night; and averaging three reliefs, (the least possible number,) we have at once an army of 54,000 men employed in the construction of lines, which, when completed, do not offer so strong a position as good redoubts, favourably situated, to command the roads and communications, connected by posts and videttes; every advantage being taken of the ground to hem in the garrison, and to strengthen these field-posts.

OBSERVATIONS ON THE COMMON MODE OF CONNECTING TH E
TOP-MASTS WITH THE LOWER-MASTS OF SHIPS, AND A
DESCRIPTION OF A METHOD BY WHICH THE GREAT EVILS
INCIDENTAL TO THE USUAL PRACTICE ARE AVOIDED.
BY MR. SAMUEL READ, OF HIS MAJESTY'S DOCKYARD, CHATHAM, AND
FORMERLY OF THE SCHOOL OF NAVAL ARCHITECTURE.

JOINTED top-masts were first used in the latter part of the reign of Henry the Eighth, since which period no alteration or improvement in the principle of connection has taken place, although the immense and destructive wring or torsion which it causes to be exerted on the heads of the lower masts, has been always felt and acknowledged by every one conversant in naval affairs.

It would be a loss of time to detail instances of mast-heads being wrung, since every naval man must be aware of the very frequent occurrence of this disaster.

The destructive strain alluded to, is evidently produced by the position of the top-mast, with relation to the lower-mast; for the axis of the former not being continuous with the axis of the latter, there will result a wring on the head of the lower-mast, whose force will be proportional to the leverage at which the top-mast acts by the cap.

These circumstances will be more clearly perceived by referring to Fig. 1 in the accompanying diagrams, where the lines cd, ef, represent the main top-mast of a 74-gun ship in its place, in which case its axis a b, is before the axis m n of the main-mast by a distance ay of about two feet six inches, and the power of the wind on the sail attached to the former is therefore, in all cases, excepting when its direction is parallel to a fore-and-aft line, ultimately employed in wringing the head of the lower-mast, by acting on the cap or lever xy. The immense angular momenta of the top-mast and of all the furniture supported by it, in the action of rolling, will also cause a similar force of torsion on the lower-mast-head, by acting at the extremity of the same lever as the ship inclines from the upright.

When it is reflected that the safety of a vessel depends, in many most urgent occasions, on the strength and efficiency of its masting, it is presumed that to effect so desirable an object as the improvement of its practical construction in relation to the particular evil adverted to, will be no inconsiderable step towards the perfection of this important branch of naval architecture; it will, however, be found, as we proceed to develope the principal features of the system I propose to adopt, that there will result many other advantages besides those chiefly aimed at.

The diagrams Nos. 2 and 3, are respectively an athwartship and broadside view of the main-mast of a 74-gun ship, showing the formation of a double head, within which and through the athwartship cap A, the top-mast H is run up on the fore side of the lower-mast, in a direction somewhat slanting, until it is high enough for its heel to be thrown aft and stepped on a metal shoe brought on the top of the spindle or core of the mast, and placed in such a position, that its axis and that of the lower-mast may be in the same right line. The spindle, instead of running up, and together with the cheeks, forming the head, as at present, is cut off about six inches above the lower edge of the trestle trees, to an inclination as shown by the dotted line pt, Fig. 3. Though cheeks, in my system, alone form the double or framed head V ROW, Fig. 2, their size athwartships being, at the trestle trees, half that of the common solid mast-head at the same place, and retaining in the fore-and-aft way the same dimensions as at present given.

The sheaves in the heel of the top-mast for the top-ropes, may either lead in planes parallel to each other in the fore-and-aft direction, or cross, as in

the present way. In the former case, the heel must be left in the foursquare; and in the latter in the eight-square; which will possess the advantage of reducing the size of the stick at this place.

The shroud pieces h, h, h, Figs. 2 and 3, are to be of elm, and are prepared for receiving the eyelets of the shrouds by affixing a fir bolster to it; the part z, z, above the bolster, being of a sufficient height to admit of the necessary number of shrouds.

Figure 4 is a plan of the upper side of the cap. The hole for the topmast is bearded away at the after part about one inch and a half, to allow the top-mast to pass through in a slanting direction. The situation of the eye-bolts for the top-ropes and top-blocks is also shown in this diagram.

Figures 2 and 3 also sufficiently indicate the method of securing the heel of the top-mast, (when swayed up to a sufficient height, and got into its place by hauling on the top-mast stay,) by shutting it between the framed or double head and the two carlings, or bars B and C, of which B is fixed, and C is moveable. The carling C may be secured in various ways, either by a stout bolt passing through the carling B on each side of the mast-head, and fore-locking on the fore-side of the carling C, or by passing lashings through eye-bolts in each. The latter method is perhaps the best, as a lashing will enable us to ease off the carling C to the required extent, when we want to trip the heel of the top-mast forward to strike it.

*

When I first digested my plan, in the year 1824, I contemplated nothing more than altering the method by which we connect the upper-masts with the lower-masts. The invention, however, of a key-fid, by Mr. Rice, of this Dockyard, which has the capabilities of adjusting the tensions of the topmast shrouds to the greatest nicety without slacking or taking in the laniards, has rendered me anxious to avail myself of the powers of his fid to produce, in conjunction with my principle, a system of masting, not only invested with additional strength in its construction, but also with facilities which could scarcely be expected, in the management and adjustment of such ponderous articles as the top-masts of the very largest ships. I have therefore, with Mr. Rice's permission, shown in the accompanying diagrams, the application of the key fid to my system of masting; and it will only require bare inspection on the part of the practical seaman, to perceive the additional advantages occuring therefrom.

From the preceding details it appears,

1st. That as the axis of the top-mast is in the same right line as that of the lower-mast; all wring or torsion on the head of the lower-mast vanishes. Hence, no other but a simple lateral strain can ever be transmitted to it by the top-mast; to resist which species of strain, the framed head here proposed is peculiarly adapted, its strength in a thwartship direction being, from the laws of mechanics, between two and three times as great as that of the common solid head; and the least strength, or that in a fore-and-aft direction, being equal to that of the common solid head.

2nd. The top-mast, top-sail yard, and all the weight attached to or sup ported by the top-mast, together with the torsion of the top-mast shrouds, stays, back-stays, &c. are brought to act, in the present system, on the lower tristle trees at some distance before the fore-side of the lower-mast head. The effort thus created must bend the head forwards, and render it necessary to set up the stay from time to time, until frequently the lower-mast becomes crippled. This evil is manifestly obviated in the proposed construction of lower-masts.

3rd. The shrouds, being brought from below the tristle trees, will not interfere with the lower yard, and a greater extent of bracing may be obtained than is usual with square-rigged vessels. The shrouds will also assume a more advantageous angle for support, and will experience a considerable reduction in length and weight. The superior strength of the framed head will admit of this desirable position of the shrouds.

4th. As the system here detailed, does not require the spindle or core of the mast to be so long as the former spindle by the whole length of the head, a considerable saving of material would be effected; and if the same principle were extended to the top-mast, its economy would be still more appreciated.

5th. That when it is required to get up a fresh top-mast at sea, it may be taken off the booms, and got in place with the greatest facility, because we are enabled to point it through the framed head. Nautical men well know the importance of facilitating this operation, which perhaps is one of the most arduous in practical seamanship.

6th. That although in changing the lower rigging, it will be necessary to take the tristle-trees, &c. off; yet, as these are much reduced in weight, and moreover the eyes of the shrouds will pass over the cap in its place, it is presumed that no more time will, on the whole, be occupied than at present. The lower tristle trees 8, 8, Figs. 2 and 3, may be secured by a couple of bolts driven hard taught and fore-locked; and the upper ones may drop over a couple of circular corks fixed in the lower tristle trees.

Described in the last Number of the U. S. Journal.