Among the most prominent of these were Trevithick and Woolf. Trevithick was the most original and speculative, Woolf the most plodding and practical, and the most successful. Trevithick's ingenuity exhibited itself in his schemes for working Boulton and Watt's pumping-engine by high-pressure steam, by means of his cylindrical wrought-iron boiler. He proposed to expand the steam down to low pressure previous to condensation, thereby anticipating by many years the Cornish engine now in use. The suggestion was not, however, then acted on, and he fell back on his original design of a simple non-condensing high-pressure engine. One of these was erected at Dalcoath mine to draw the ores there. It was called "the puffer" by the mining people, from its puffing the steam direct into the air; but its performances did not compare favorably with those of the ordinary condensing engines of Boulton and Watt, and the engine did not come into general use. Trevithick was not satisfied to carry on a prosperous engine business in Cornwall. Camborne was too small for him, and the Cornish mining districts presented too limited a field for his ambitious spirit. So he came to London, the Patent-office drawing him as the loadstone does the needle. In 1808 he took out two patents, one for "certain machinery for towing, driving, or forcing and discharging ships and other vessels of their cargoes," and the other for "a new method of stowing cargoes of ships." In 1809 he took out another patent for constructing docks, ships, etc., and propelling vessels. In these patents, Trevithick was associated with one Robert Dickinson, of Great Queen Street, but his name stands first in the specification, wherein he describes himself as "of Rotherhithe, in the county of Surrey, engineer." By the first of these patents he proposed to tow vessels by means of a rowing wheel shaped like an undershot water-wheel furnished with floats placed vertically in a box, and worked by a steam-engine, which he also proposed to employ in the loading and unloading of the vessel, but it is not known that the plan was ever introduced into practical use. The patent of 1809 included a floating dock or caisson made of wrought-iron plates, in which a ship might be docked while afloat, and, after the water had been pumped out of the caisson, repaired without moving her stores, masts, or furniture. This invention has since been carried out in practice by the Messrs. Rennie in the floating iron dock which they have recently constructed for the Spanish government. Another invention included in the specification was the construction of merchant and war ships of wrought-iron plates strongly riveted together, with their decks supported by wrought-iron beams, and the masts, bowsprits, and booms also of tubular wrought iron, thereby anticipating by many years the form and structure of vessels now in common use.