'No. XVI.--How to make a sea castle or a fortification _cannon proof_, capable of a thousand men, yet sailable at pleasure to defend a passage, or in an hour's time to divide itself into three ships, as fit and trimmed to sail as before; and even whilst it is a fort or castle, they shall be unanimously steered, and effectually be driven by an indifferent strong wind.' It is to be regretted that Parliamentary or other inducements were not employed to obtain from the marquis, at least the publication of his views as regards making vessels cannon proof. From the general character of his inventions, and from comparison of them, it appears he had full faith in cannon-proof floating batteries as a means of defence, and, we may consequently and justly infer, as superior to the latter. Among his inventions there are but two in reference to 'fortifications,' and both of these are after a manner a transfer of the floating battery to land, or an application of the principle of mobile defences. These are as follows: 'No. XXIX.--A portable fortification, able to contain five hundred fighting men, and yet, in six hours' time, may be set up and made cannon proof, upon the side of a river or pass, with cannon mounted upon it, and as complete as a regular fortification, with halfmoons and counterscarps. '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 (the bulwark) contain but four pieces, they shall be able to discharge two hundred bullets each hour.' There can be but little question, from all I have cited, that the Marquis of Worcester was singularly in advance of his age as regarded the great principles of warfare. We have found him thus far, in all probability, acquainted with the construction of permutable seals, and indeed of the grand principle of permutation applied to technology in several respects (vide "Century" Nos. III, IV, V,) of the telegraph, of sinking vessels by torpedoes, and, finally, of floating batteries and cannon-proof vessels. In No. 30, we have, however, a hint that the marquis had studied the principles of revolving firearms, when he speaks of four cannon discharging two hundred bullets each hour. That he had, theoretically, at least, anticipated Colt, appears from 'No. LVIII.--How to make a pistol discharge a dozen times with one loading, and without so much as once new priming requisite, _or to change it out of one hand into the other_, or stop one's horse.'