It is difficult to attempt an elucidation of this or the following articles; but the annexed extract from the General Evening Post for 1747 appears to throw some light on No. XXX.
"On the 11th instant, Mr. James Allis was presented to the Royal Society, with a new invented cannon, which charges and discharges both at one time, and twenty times in a minute: he had their thanks, and a handsome present."
No. XXX.
A way, in one night's time, to raise a bulwark, twenty or thirty foot high, cannon proof, and cannon mounted upon it; with men to overlook, command and batter a town; for, though it contain but four pieces, they shall be able to discharge two hundred bullets each hour.
NOTE.
Vide the preceding Article.
Since writing the above, the Editor has been called to witness the effects of highly elastic vapour applied to the propelling of leaden bullets, in an apparatus contrived by Mr. Perkins; and these destructive missile engines are capable of discharging nearly two hundred bullets, in one sixtieth part of the time described by our author in the present Article.
No. XXXI.
A way how safely and speedily to make an approach to a castle or town-wall, and over the very ditch, at noon-day.
NOTE.
A wheel carriage, of sufficient strength to support an heavy iron tower, must first be provided. It may be constructed of thick wrought iron, with door, &c., of the same material, and hung round with sand-bags, through the interstices of which may project from six to eight small guns to protect it from musquetry. The most eligible method of moving the tower appears to be by fixing small handles to the axles of the wheels, which may be turned at pleasure by those within the walls. To prevent any attempt of the enemy who may sally forth to drag the machine within the walls of the town, &c., it will be adviseable to arm the wheels with long steel studs, which, when the handles are fastened within, will render it immoveable.
This tower, though but of little use in modern warfare, appears well adapted for reconnoitring the walls of a fortified town, and, if fixed upon a hollow iron vessel, will possess the further advantage of crossing rivers and moats. Nearly similar machines are described by Vitruvius, and other authors who treat on military engineering.