"They were put in hand in the mine, and I worked about them; they were wrought-iron cylindrical boilers, about 20 feet long, and 5 or 6 feet in diameter; the fire-tube was about 3 feet in diameter; the fire returned around the outside in brick flues. Three boilers were put in side by side.
"When Captain Dick first tried them, he said to the men, Now mind, the fire-bars must never have more than six inches of coal on them; give a shovel or two to one boiler, and then to another. When Captain Dick's back was turned, the men said they wasn't going to do anything of the sort, there would never be no rest for them. They used to say that the boilers saved more than 170l. the first month."[73]
Clark, when a boy, in 1799, helped to construct Trevithick's globular boiler in Dolcoath, and recollected the events of the few following years, during the contests with the whim-engines about 1806, and the introduction of the large cylindrical wrought-iron boilers for the pumping engines in 1811, and the struggle preceding the downfall of the Watt low-pressure steam vacuum engine, to make room for the high-pressure expansive steam-engine, with or without vacuum.
"About 1812 Captain Trevithick threw out the Boulton and Watt waggon boilers at Dolcoath and put in his own, known as Trevithick's boiler. They were about 30 feet long, 6 feet in diameter, with a tube about 3 feet 6 inches in diameter going through its length. There was a space of about 6 inches between the bottom of the tube and the outer casing. Many persons opposed the new plans. The Boulton and Watt low-pressure engine did not work well with the high steam, and the water rose in the mine workings. Captain Trevithick, seeing that he was being swamped, received permission from the mine managers to dismiss the old engine hands and employ his own staff. Captain Jacob Thomas was the man chosen to put things right. He never left the mine until the engine worked better than ever before, and forked the water to the bottom of the mine. Before that time the average duty in the county by the Boulton and Watt engines was seventeen or eighteen millions, and in two or three years, with Trevithick's boilers and improvements in the engines, the duty rose to forty millions. About 1826 he (Captain Vivian) was manager of Wheal Towan; their engines were considered the best in the county, doing eighty-seven millions; they had Trevithick's boilers, working with high-pressure steam and expansive gear; few if any of Boulton and Watt's boilers could then be found in the county. Sir John Rennie and other scientific men, who doubted the reports of the duty, came and made their own trials with the engines, and were satisfied that the duty was correctly reported.
"About that time a Mr. Neville requested him to report on the engines at his colliery at Llanelthy; one was an atmospheric of Newcomen's, doing six millions; and four or five of Boulton and Watt's patent engines averaged fourteen millions."[74]
When at last the cylindrical high-pressure boiler was admitted, and men had been taught to fire them, many persons still liked the old plans, and among them the easy-going low-pressure enginemen. The consequence was that the Watt engines under their management refused the early doses of Trevithick's high steam, not easily digesting it, and their obstinacy nearly swamped Trevithick and his plans.
"When a little boy, about 1812, I frequently carried my father's dinner from Penponds to Dolcoath Mine. One day, not finding him in the engine-house, I sought him in the account-house, but not knowing him in a miner's working dress, refused to give him his dinner. William West then worked with him. I heard there was difficulty in making the new boilers and the old engine work well; engineers from other mines looked on from a distance, not liking the risk of explosion. People seemed to be against the new plans; some labourers worked with them."
This narration—sixty years after the events—from Mr. Richard Trevithick, the eldest son of the engineer, shows that William West helped in applying high-pressure steam to the Watt low-pressure engine, and that but few sympathized with the innovators on old customs; but among them was Captain Jacob Thomas, who successfully fed the old engine with strong steam.
At that time the Watt engines in Cornwall had been doing seventeen or eighteen millions; Trevithick's new boilers increased their duty to forty millions.
"William Pooly[75] was working in Dolcoath before Captain Trevithick's new boilers were put in, and helped to put them in.