then excavated before the air has been renewed in the enemy's gallery; they try to find the ruins of it, and enter and attack it vigorously, and retrenchments are made as in the former case.

In applying to galleries which have been seized the rule before given, Belidor converts them into trenches, and thus gains considerable cover, safe communications, and immense parallels, through which he proposes to lead the troops.

This method of attack is doubtless ingenious, and easy of application: it can be employed in many instances, and its effect would be decisive; it would not only destroy the galleries belonging to the besieged, but also the retrenchments and barricades that might be built by them.

It cannot, however, be expected that by this method exclusively a system of countermines can be destroyed. The besieger would in reality be obliged to renew frequently his attacks, so as to become master of the gallery; and it must be admitted that if the besieged knows how to make use of his position, the result of these combats would be often uncertain. Belidor has perhaps attached too much importance to his discovery, in applying it to all the systems of mines known in his time, the attack of which he has described, according to his new method, in his manuscript treatise on Subterranean Warfare.

This idea of taking places by means of their own mines appeared so engaging to him, that he proposed the building of galleries to places devoid of them, so as to convert them afterwards into trenches. As experience teaches us that a sapper can advance 160 yards above-ground in twenty-four hours, while a miner can scarcely build 4 yards of gallery in the same time, it is very doubtful whether this last idea of Belidor is within the limits of probability.

The History of Sieges' gives several examples analogous to those proposed by our author; and he himself affirms that in the war of 1701 the allies had recourse to a sort of covered sap, which they made use of with success at the sieges of Tournay and Bethune.

They advanced boldly, he says, between two horn-works, without running any risk from the tremendous fire kept up from the branches of these works, and arrived as far as the salient angle of the covered-way. They went under-ground to the depth of 2 or 3 yards by means of straight galleries 3 feet wide, feet high, and 2 yards in length when these small portions of galleries were completed, the earth above was blown away, then widened, and zig-zags excavated where necessary.

This example, although not very different from mining, may find applications in the attack of places liable to inundations, and which can only be approached by means of dykes or narrow causeways.

SECTION V.-ON THE FORMATION OF BREACHES BY MINES.

Since artillery has been so greatly augmented in armies, breaches have been made by guns in fortified places.

The method of making breaches by mines being slower, more dangerous, and less certain, has been abandoned in the present age. As, however, instances may occur in which an army without artillery finds itself obliged to carry an important post surrounded by a scarped wall, it is necessary to give some details on this subject.

When the besieger has established himself on the crest of the covered-way, and has effected a descent into the ditch, he pushes forward a sap to the foot of the revetment of the work he is attacking, supposing the ditch to be dry; if not, he ought to fill it up, and construct an epaulement on the side of the flank, as is done Plate VII. at the attack of places. He then places against the revetment the planks c (fig. 1),

Plate VII.

2 or 3 yards long, 1 foot wide, and 4 inches thick these are covered with tin, to resist fire they are made to lean against the wall, leaving sufficient room for two miners to rest conveniently, and work at their ease. Finally, the besieger covers them with raw hides, and forms an epaulement with sand-bags, to protect the men from the fire of the collateral works.

The miners, under cover of the planks, then work to break through the revetment, and bury themselves in the wall as fast as possible. The entrance, or 'eye of the mine,' as it is technically called, ought to be a foot above the level of the water,— supposing that the enemy have no means of raising it by inundating the ditch: without this precaution, there is a risk of the work being inundated; and, as a general rule, the miner should always commence work one foot above the level of highest water.

When it is possible to erect a battery of one or two guns on the covered-way, to cover the miner, the opportunity should not be lost. In aiming constantly at the same spot, a hole 1 or 2 yards deep is soon opened, into which the miner gets, and is soon under cover from the fire of artillery or musketry from the flanks, as well as shells and grenades, which are rolled down upon him from the top of the rampart. He has then only the sorties and the mines of the besieged to fear.

The miner ought to enter the revetment by a horizonal gallery at right angles to the direction of the face of the work which he is entering: this little gallery is 3 feet high by 2 feet broad. When he gets to the earth of the rampart, he drives two galleries, right and left, which are directed along the inner side of the revetment wall, and which are 2 feet 6 inches high and 2 feet wide; their length varies according to the thickness of the wall, and the mines placed at their ends should be so regulated that their lines of least resistance may meet at a point.

At the end of the branches, the chambers of the mines are dug so that one-half of them is in the masonry of the wall. Vauban states that this is the best method of obtaining the greatest effect: when mines can be established in the counterforts, care is taken to do so. A twofold advantage is gained by this; the powder acts with more certainty on the outside of the revetment, at the same time that the counterforts destroyed completely leave the earth to support its own weight.

When the chambers of the mine are completed, the powder is brought up in sandbags; they are then loaded and tamped. The firing should be simultaneous, in order that the explosion of the mines taking place together may produce the more considerable results.

Fig. 2 shews instances of mines thus bored in the thickness of the rampart it is taken from a treatise by Vauban. Other mines, besides those behind the revetment, are there shewn in the earth, to render more certain the overthrow of the revetments, and to facilitate the ascent of the breach.

It may happen that behind the revetment where the mine is commenced, a gallery a or b (fig. 1) may exist. In this case the besieged can annoy his enemy greatly, and retard considerably the placing of the mines. The besieger ought then to try to break into the gallery, by means of a petard, when there is before him only a slight partition of masonry. When he once effects an entrance, grenades and fire-balls should be thrown in, to drive away the enemy for at least some time he then widens the opening, and prepares to attack the gallery by storm. If he drives the enemy out altogether, or partly, he retrenches himself, and then commences establishing a mine. When the gallery in the wall of the escarp is sufficiently retired towards the interior of the work, the besieger may then save a great deal of time and trouble by sacrificing a proportionate quantity of powder. It will only be necessary to form a breach, to close the two ends of the gallery (if open at two ends) by sand-bags and logs of wood

Plate VII.

laid across, and to collect in the space between a great quantity of powder in heaps. The explosion will bring down the whole of the face of the work. Some proofs of this expeditious mode of proceeding have been made.

In the preceding it has been supposed that the wall required to be opened has earth at the back; but it may happen that a breach is required to be made in a castle situated in a defile where cannon cannot be transported.

In this case, suppose a a, fig. 2, to be a wall first required to be opened for a mine; the thickness must be ascertained as nearly as possible; a gallery b is then commenced at the foot of the wall, which is driven to the middle of it; returns are made at right angles to this gallery, and at the end of them are placed the mines cc: the explosion of these taking place simultaneously will throw down a greater portion of the wall.

This supposes the wall to be 3 or 4 yards thick; but if it be only 2 yards or less, it will be necessary to establish one or more mines under the foundation, supposing the ditch to be dry, taking care to place them in the middle of the whole width. To overthrow a wall only 2 or 3 feet thick, it is sufficient to place one or more barrels of powder against it.

APPENDIX I.

Observations upon Mine Frames for Field Service.*

When the mining practice commenced at Chatham, in the year 1812, the system which was then adopted was not that now in use, called 'chassis à la Hollandaise,' but the earth of the galleries was supported by means of a frame of peculiar construction, admirably suited to the purpose, resembling in some respects a common door-frame.

This frame was composed of a capsill of from 4 to 6 inches in depth (according to the size of the gallery) and 4 inches in width; of stanchions 4" x 4" and of groundsills 4" x 2"; and they were put together without nails or screws, or other fastenings, and were not subject to derangement.

The frames were placed at intervals of from 3 to 4 feet apart, according to the nature of the soil, and formed the support of a series of planking, 9 inches wide and 2 inches thick, called the top sheeting,' which was lodged upon the capsills, and of other planks, 9 inches wide and 14 inch thick, which supported the sides of the gallery, and were called the 'side sheeting.'

On the bottom of the gallery, the groundsills alone rested, and were let into the floor, so as to be flush with the surface of the ground.

Some years later, for some reason which I have never understood, this system (which was copied by some of the continental nations) was abandoned by us, and recourse was had to the system called the chassis à la Hollandaise.'

This is a case composed of 4 pieces of plank, of from 1 to 2 or 2 inches in thickness (according to the size of the gallery), and the width depends upon that of the planks which can be obtained.

The form of this case is rectangular, and both the capsill and groundsill have two notches at each end, while at each end of both the stanchions, there are tenons corresponding to those notches.

Each of the stanchions is hollowed out on both edges near the middle of its length, to admit of its being more easily handled by the miner, and for pickets being driven through the opening thus formed into the sides of the gallery, to keep the stanchions more steadily fixed when used for the support of ascending or descending mines. In the practice at Chatham it is found necessary to cut away more of the head of

VOL. II.

By M.-Gen. Sir Frederic Smith, R.E.

D D

the gallery than the mere height for the case when placed, to allow of its clearing the top of the tenon in the act of placing it, after which it is dropped into its place; therefore an interval is obliged to be left between the upper surface of the capsill and the earthen roof of the gallery, equal in depth to the height of the tenon.

It was found that this gave the opportunity for a settlement of the ground; and this induced Serjeant-Major Jones* to suggest an alteration of the frame, which, to a certain extent, is an improvement.

It will be seen, from what has been stated above, that a capsill will answer the purpose of a groundsill, and that the stanchions are suitable to either side of the gallery. In Serjeant-Major Jones's proposition, one end of the groundsill had a notch cut in it, to receive the tenon of one of its stanchions, that stanchion having two tenons. The other end of the groundsill has a cleat nailed upon the surface, in a position corresponding with that of the notch at the other end. The stanchion for this side has also a notch cut to fit over this cleat, and at the other end of the stanchion there is a tenon, like that on the opposite side of the case. The capsill has a notch at either end, to receive the corresponding tenon.

N: I. A.

No I. B.

NOI. C.

In placing this case the groundsill is first bedded, then the left stanchion is placed perpendicular to the groundsill, one of the tenons being inserted into the notch. The

capsill is then placed so that its left notch receives the upper tenon of the left stanchion, and then the tenon of the right stanchion is partially inserted into the corresponding notch of the capsill; but this stanchion is inclined, with its heel approximating to

* Late Quarter-Master, Royal Engineers, now Captain half pay.

that of the stanchion previously fixed, and is then gradually slid along the surface of the groundsill till its notch passes over the cleat, when two pickets are driven through mortise-holes on either side of the cleat, to keep the stanchion from being forced out of its proper position.

This system gives a facility not only in placing the frames, but in removing them for the purpose of tamping a gallery, which is often a difficult operation, if there be much pressure of ground on the capsill in the old system.

The disadvantage of this plan is, that the stanchions are not of universal application, being of different form; the one having two tenons, and the other only one.

The groundsill will answer for the capsill, if both are supplied; but if by any want of arrangement either should be deficient, a superabundant quantity of the other will not supply its place.

A consideration of Serjeant-Major Jones's proposal led to a simplification of the mine case, which may be described as follows.

In the first place, the groundsill and capsill are identical in form. Each has a rebate at both ends, of the same width as the thickness of the stanchions, and running across the whole width of the plank, its depth being half an inch. The stanchions are mere rectangular pieces of board, without any workmanship whatever upon them, excepting an auger-hole through the centre of each, for the purpose of picketing them to the sides of the gallery.

As in the former instance, the groundsill is first lodged in its position; then one of the stanchions, with its end resting on the flat surface of the rebate; afterwards the capsill is placed with the rebate at one end resting upon the upper edge of the stanchion; and lastly, the opposite stanchion has its upper end placed in contact with the corresponding rebate of the capsill, whilst the lower extremity or heel of the stanchion rests upon the middle of the groundsill, and is gradually moved along its surface, until it drops into the rebate at its own end.

So far as simplicity of construction and the more general application of its parts are concerned, this case appears to be an improvement upon that of Serjeant-Major Jones for galleries and branches, but it is not, like his, applicable to shafts.

With the simple case last described, the excavation will be very little more than that required for Serjeant-Major Jones's case,-merely the extra half-inch at one side, to allow of the depth of the rebate; but practically this is of no importance.

In the mining operations of the year 1847, at Chatham, the cases of all three descriptions were in common use; and as there was an abundance of each at hand, with a store suitably placed with reference to the work, no inconvenience or confusion arose from the misplacing of the several parts employed.

Any practical miner, capable of using a saw, could make the more simple case without difficulty; and it is obvious, that in preparing these cases there is a considerable saving of time.

For preparing this case, the only tools required are the saw and the auger: and in the other, the following addditional tools would be necessary, viz. a gimlet, a hammer, a chisel, and a mallet, with nails.

In very loose soil, it is found difficult to drive a gallery supported by either description of case that has been described; whereas there is scarcely any soil (but a running sand) in which the original frame and planking of 1812 could not be used.

In the old system in question, the planks were inserted over the heads of the capsills, and behind the sides of the stanchions, and were driven gradually forward in advance of the workmen, by means of chases cut out with a push-pick; false frames being occasionally used, to support the more advanced ends of the planks. I believe, on the whole, that the old plan was the best. F. S.