486 Mr. Henwood on the Cornish Pimping-Engines. 



was passed over the cylinder-cover; under the steam-pipe 

 from the boiler was a similar fire, and its smoke was conveyed 

 round the pipe for some distance. Such parts of the engine 

 as were not enveloped by the flues were surrounded with 

 saw-dust*, and the boilers were covered with ashes as at 

 Huel Towan. 



The eno-ine at East Crinnis had neither steam nor heated 

 air passed round it; but every part which contained dense 

 steam was surrounded with a very thick covering of saw-dust, 

 and the boilers were protected in a similar manner to those 

 of the other engines. 



On all these the indicator was placed; and also on Burn's 

 eno-ine at Binner Downs, which is inclosed in a similar man. 

 ner to Swan's engine on the same mine, already mentioned ; 

 and on Trelawny's and Borlase's engines at Huel Vor, both 

 which have steam-cases and other coverings like that described 

 at Huel Towan. On the duty of these no experiments were 

 made. 



Table I. — (Constants.) 



Dimensions of the Engiiies, and amount of their loads. 



* In the progress of my experiment, the saw-dust on the cylinder-cover 

 ignited several times. The influence exercised on the steam within the 

 cylinders by the media with which they were suri'ounded, may be discovered 

 by an inspection of the diagrams. (Trans. Inst. C. E. Vol. ii. Figs, 4., &c., 

 PI. IV.) 



f The stroke in this pump is but 5-5 feet. 



\ From Captain Lean's " Monthly Reports." 



