xv.] BULL'S DIRECT-ACTING ENGINE. 185 inches and twenty-four inches in diameter, and the strokes six feet and eight feet respectively. This engine does not appear to have been a success. Watt, however, proceeded to Bristol, and cautioned Hornblower's employers, and the public, against using this form of engine, as being a direct infringement of his patent.2 Hornblower's next engine was not erected till 1790. It was at the Tin Croft mine, near Redruth.3 This engine acted well, and in 1792 Hornblower applied to Parliament for an extension of his patent, but the application was refused through the opposition of Boulton and Watt.4 The form of Bull's engine is shown in Fig. 39. It acted in a precisely similar manner to Watt's singleacting engine, only that the inversion of the cylinder caused the operations to be reversed to some extent. The steam from the boiler was admitted under the piston, while the vacuum was produced above it. The weight of the pump-rods brought the piston back to the bottom of the cylinder, the steam in the meanwhile 1 Farey on the Steam Engine, p. 388. 2 Smiles's Lives of the Engineers-" Boulton and Watt," ed. 1874, pp. 256-7. Both Hornblower and Bull employed the separate condenser in their engines. 3 Farey on the Steam Engine, p. 387. Pole on the Cornish Engine, p. 37. An Address to the Mining Interest of Cornwall, by Thomas Wilson, 1793. 4 Pole on the Cornish Engine, p. 38. Farey on the Steam Engine, p. 389. CH. XV.] VICTORY OF BOULTON AND WATT. 187 flowing through the equilibrium-valve, and filling the cylinder above the piston. In 1793 Boulton and Watt instituted legal proceedings against Bull, founded on an engine he had erected at Oatfield mine. The verdict was for the plaintiffs, subject to the opinion of the Court as to the validity of their patent. The special case was tried in 1795, but the opinions of the judges were equally divided, and no decision was given. In the meantime Hornblower had continued to erect his engines, and his opposition had become so formidable to Boulton and Watt as to compel them to bring an action against him. The cause was tried on the 16th of December, 1796, when a verdict was again given for the plaintiffs, subject, as in Bull's case, to the opinion of the judges. The final hearing came on in January, 1799, close upon the expiration of Watt's patent, when the validity of the patent was established by the unanimous opinion of the four judges. The great importance of the case to Boulton and Watt may be inferred from the fact that they are stated to have recovered 40,000l. for arrears of patent dues.1 The partnership of Boulton and Watt had proved a remarkably happy one. It is not too much to say 1 Pole on the Cornish Engine, pp. 36-39; Muirhead's Life of James Watt, 2nd ed., pp. 389-403; Mechanical Inventions of James Watt, Vol. III., pp. 164-292. that the commercial success which attended the introduction of Watt's invention was in a large measure due to the favourable conditions under which it was brought out. The wealth and influence, the energy and tact, of Boulton, were invaluable complements to the inventive genius of Watt. On the expiration of the term of twenty-five years, during which they had held the monopoly of the invention, the partnership was dissolved, Boulton and Watt retiring from the business and handing it over to their sons. The encomiums which have been pronounced upon Watt and his invention, are too numerous and well known to require more than a passing allusion. Sir Walter Scott, Sir Humphry Davy, Lord Brougham, Lord Jeffrey, and others of the most distinguished of his contemporaries in literature and science, have celebrated the praises of the illustrious inventor. The account of the steam engine, however, given by Dr. Erasmus Darwin, in his Botanic Garden, is possessed of considerable historic interest, both from the date at which it was written (1789), and also from the fact of its having been the subject of correspondence between Watt and his friend Darwin, who had applied to him for materials for his poem.' Dr. Darwin reviews the 1 "I intend to publish the Economy of Vegetation in the spring: says Darwin, in a letter to Watt dated November 20th, 1789,-"now in this work I shall in a note mention something about steam engines. If you will at a leisure hour tell me what the world may xv.] EXTRACT FROM THE "BOTANIC GARDEN." 189 invention of the engine, recounts the uses to which it was put at the time when he wrote, and gives a prophetic forecast of the future that lay before it, in the following lines :— "Nymphs! you erewhile on simmering caldrons play'd, And call'd delighted SAVERY to your aid; Bade round the youth explosive STEAM aspire In gathering clouds, and wing'd the wave with fire; Quick moves the balanced beam, of giant birth, "The giant-power from earth's remotest caves Gale after gale, He crowds the struggling wind; know about your improvements of the steam engine, or anything about your experiments, or calculated facts about the power of your engines, or any other ingenious stuff for a note, I shall with pleasure insert it, either with or without your name," &c. In his reply, dated November 24th, 1789, Watt says to Darwin :—“I know not how steam engines come among the plants; I cannot find them in the Systema Naturæ, by which I should conclude that they are neither plants, animals, nor fossils, otherwise they could not have escaped the notice of Linnæus. However, if they belong to your system, no matter about the Swede; and your kind attention to us will certainly make me furnish you with all the necessary materials for poetic readers," &c.-Mechanical Inventions of James Watt, Vol. II., pp. 230, 232. |