Plate 8, Fig. 1, represents one of the most important uses that can be made of Rockets for field service; it is that of the Rocket Ambuscade for the defence of a pass, or for covering the retreat of an army, by placing any number, hundreds or thousands, of 32 or 24-pounder shell Rockets, or of 32-pounder Rockets, armed with 18-pounder shot, limited as to quantity only by the importance of the object, which is to be obtained; as by this means, the most extensive destruction, even amounting to annihilation, may be carried amongst the ranks of an advancing enemy, and that with the exposure of scarcely an individual. The Rockets are laid in rows or batteries of 100 or 500 in a row, according to the extent of ground to be protected. They are to be concealed either in high grass, or masked in any other convenient way; and the ambuscade may be formed of any required number of these batteries, one behind the other, each battery being prepared to be discharged in a volley, by leaders of quick match: so that one man is, in fact, alone sufficient to fire the whole in succession, beginning with that nearest to the enemy, as soon as he shall have perceived them near enough to warrant his firing. Where the batteries are very extensive, each battery may be sub-divided into smaller parts, with separate trains to each, so that the whole, or any particular division of each battery, may be fired, according to the number and position of the enemy advancing. Trains, or leaders, are provided for this service, of a particular construction, being a sort of flannel saucissons, with two or three threads of slow match, which will strike laterally at all points, and are therefore very easy of application; requiring only to be passed from Rocket to Rocket, crossing the vents, by which arrangement the fire running along, from vent to vent, is sure to strike every Rocket in quick succession, without their disturbing each others’ direction in going off, which they might otherwise do, being placed within 18 inches apart, if all were positively fired at the same instant. Fig. 2 is a somewhat similar application, but not so much in the nature of an ambuscade as of an open defence. Here a very low work is thrown up, for the defence of a post, or of a chain of posts, consisting merely of as much earth and turf as is sufficient to form the sides of shallow embrasures for the large Rockets, placed from two to three feet apart, or nearer; from which the Rockets are supposed to be discharged independently, by a certain number of artillery-men, employed to keep up the fire, according to the necessity of the case.