POLE STEAM-ENGINE. 75 



was not much out of my way, so I drove the bullocks across 

 Herland Common toward the engine-house. Just as the 

 bullocks came near the engine-house the engine was put to 

 work. The steam roared like thunder through an underground 

 pipe about 50 feet long, and then went off like a gun every 

 stroke of the engine. The bullocks galloped off some one way 

 and some another. I went into the engine-house. The engine 

 was a great pole about 3 feet in diameter and 12 feet long. A 

 cast-iron cross-head was bolted to the top of the pole. It had 

 side rods and guides. A piece of iron sticking out from the 

 cross-head carried the plug-rod for working the gear-handles. 

 The top of the pole worked in a stuffing box. A large balance- 

 beam was attached to the pump-rods, near the bottom cross-head. 



" There were two or three of Captain Trevithick's boilers 

 with a tube through them, the fire in the tube. They seemed 

 to be placed in a pit in the ground. The brick flues and top of 

 the bricks were covered with ashes just level with the ground. 

 A great cloud of steam came from the covering of ashes. 



" I should think the pressure was more than 100 Ibs. to the 

 inch. People used to, say that she forked the mine better than 

 two of Boulton and Watt's 80-inch cylinder engines. We could 

 hear the puffer blowing at Gurlyn, five or six miles from the 

 Herland Mine. 



" In 1813 I carried rivets to make Captain Trevithick's 

 boilers in the Mellinear Mine ; they were 5 feet in diameter and 

 30 or 40 feet long, with an internal fire-tube. It took four or five 

 months to build them. In the present day (1869) a fortnight 

 would build them. The largest boiler-plates obtainable were 

 3 feet by 1 foot. We had to hammer them into the proper 

 curve. The rivet-holes were not opposite one another. A 

 light hammer was held against the rivet-head in riveting, in 

 place of the present heavy one, so the rivet used to slip about, 

 and the plates were never hammered home so as to make a 

 tight joint." 1 



Lest the reader should doubt the comparative power 

 of the Watt low-pressure vacuum and Trevithick's high- 



1 Recollections of Mr. James Bun Held, Penzauce, 1871. 



