86 POLE STEAM-KXG1NK. 



Trevithick' s figures show the working power of the 

 33-inch pole as much greater than Watt's 72-inch 

 cylinder engine, even when the steam pressure in the 

 former was much reduced, and that Woolf s double- 

 cylinder engine, of less power, cost ten times as much 

 as the pole-engine. This sum probably included the 

 costly buildings required for the beam-engines, which 

 Trevithick's plan dispensed with. 



The reader may judge of the perfection of mechanism 

 in this plain-looking engine from the fact that a pole, 

 with 150 Ibs. of steam to the inch in the boiler, was 

 equal to 50 or 60 tons weight, thrown up and down its 

 10-feet stroke ten or fourteen times a minute, with a limit 

 of movement perfectly under control, while modern 

 engineers are building ships' turrets because of the 

 difficulty of raising and depressing a 30-ton gun from 

 the hold to above the water level. 



[Hough draft.] 



" SlR, " CAMBORNE, September !2tJi, 1815. 



"I received a letter dated the 20th of August, from 

 Mr. Uavies, in which he did not mention the name of Herland 

 castings. On the 24th of the same month I wrote to you, in- 

 forming you of the same, and requesting to know what state of 

 forwardness the castings were in. On the 30th of August I 

 received another letter from Mr. Davies, not saying what state 

 of forwardness the castings were in, nor when they would be 

 finished, only that they would set their hands about them, and 

 that I might expect a letter from you stating the particulars, 

 which has not yet come to hand. I have waited so long that I 

 am quite out of patience. You will know that it is now nearly 

 double the time that the castings were to have been finished in, 

 and you have not yet answered my letters as to the state of the 

 castings nor when they will be finished. I must again request 

 you to write to me on this subject, otherwise I must immedi- 

 ately remove the orders to some other founders that may be a 



