POLE STEAM-ENGINE. 103 



stroke than the piston, because it was fixed inside the cylinder, 

 nearer to the centre of the beam. There was" a pole-engine 

 then working at Wheal Lushington, also at Poldice, and at 

 Wheal Damsel." 



" Captain Artha recollects at Wheal Alfred Mine in 1812 

 the 66-inch cylinder pumping engine used a pole air-pump ; one 

 or two whim-engines on the same mine also used them. Wheal 

 Concord pumping engine, in 1827 had a similar air-pump. Old 

 Wheal Damsel, near Treloweth, used one as late as 1865. The 

 condensing water and air passed through a branch with a valve 

 on it near the top of the pole-case, just under the stuffing box 

 There was a foot-valve at the bottom of the pole-case." 1 



The writer has had the pleasure of personal acquaint- 

 ance with each of those three gentlemen, who as young- 

 engineers commenced their labours in the erection of 

 Trevithick's engines. 



No sooner had Trevithick perfected the pole con- 

 densing engine and then the pole puffer-engine, than 

 he, in conjunction with Sims, who had just taken part 

 in the erection of one of his high-pressure steam pole- 

 engines for working the pumps at Beeralstone Mine, 

 combined the pole with the ordinary Watt vacuum 

 engines, supplying them with steam from his high- 

 pressure boilers, in other words, converting them from 

 their original form of low-pressure vacuum engines to 

 high-pressure expansive compound steam-engines. 



The old 60-inch cylinder Boulton and Watt engine, ' 

 at Wheal Chance (one of Watt's favourite engines), was 

 in 1818 transformed into a high-pressure engine, with 

 Trevithick's pole placed between the centre of the main 

 beam and the steam-cylinder. The high-pressure steam 

 from Trevithick's new boilers was turned under the 



1 Captain Artha became the resi- I engineers ; and Mr. Burral, the engi- 



dent engineer at the Real del Monte , neer of a department at the eno-ine- 



inines in Mexico; Captain Samuel works of Messrs. Harvey and Co. 



(irose, one of the lirsl Cornish mine 



