The promised book was never written, and we are accordingly left in uncertainty as to the precise character of the Marquis’s inventions. That he had a full conviction of the great powers of steam, as well as of its manageability and extensive practical uses, is sufficiently clear; but that he ever erected any engines after the plans thus summarily described is matter of considerable doubt. It is remarkable that, notwithstanding the number and variety of his suggested inventions, not a single model or machine constructed by the Marquis or his skilled workmen has been preserved. Mr. Dircks, who has collected and published all that is likely to be brought to light relative to the life and works of the Marquis, and has laboured at his task with a rare love and enthusiasm for his subject, naturally expresses surprise that “none of the many cabinets of the curious seem to have possessed any model or work of his production; not even the indefatigable Tradescant, although his museum was at Lambeth.”[14] But it is probable, as we have already observed, that the Marquis’s ‘Scantlings,’ notwithstanding his statement that he had “tried and perfected” the inventions of which he speaks, were rather the foreshadowings of things to come than the descriptions of things that had actually been executed. Thus, no one pretends that the Marquis ever constructed a steamboat, and yet his description of a vessel “to work itself against wind and tide, yea, both, without the help of man or beast,” can apply to nothing else.[15] “This engine,” said he, “is applicable to any vessel or boat whatsoever, without being therefore made on purpose, and worketh these effects: it roweth, it draweth, it driveth, (if need be) to pass London Bridge against the stream at low-water, and a boat laying at anchor, the engine may be used for loading or unloading.” But it would not be possible for any one to make an engine after the description given in the ‘Scantlings;’ and to a generation unacquainted with the powers of steam, his suggestions would be altogether without meaning. [14] Dircks’s ‘Life and Times,’ &c., 356. The strongest evidence which could be adduced of the ambiguity of the Marquis’s ‘Articles’ is to be found in the fact that the various ingenious writers who have given plans of his supposed engine have represented it in widely different forms. Farey assumes that it worked by the expansive force of steam; Bourne, that it worked by condensation and atmospheric pressure; Dircks infers that it included such ingenious expedients as valves and even a four-way cock, worked by a lever-handle; Stuart, that it contained a cylinder and piston, and was, in fact, a complete high-pressure lever-engine. Again, the drawings of the various writers on engineering who have attempted to reproduce the engine--of Stuart, Galloway, Millington, and Dircks--differ in essential respects.