172 Mr. Pattinson on the Action of Steam 



when the excitation is very good, the spark is much longer.' 

 This glass, as Dr. Priestley observed, is more poweifully ex- 

 cited than the finer sorts, and its power is but little affected 

 by a moist atmosphere. 



XXV. On the Action of Steam and Quick-lime upon heated 

 Galena. Bij Mr. H. L. Pattinson, Alston, Cumberland. 



To the Editors of the Philosophiccd Magazine and Annals. 

 Genllemen, 

 "pERHAPS nothing has contributed more to the great ad- 

 -*■ vancement of knowledge within the last few years, than the 

 rapid exchange and diffusion of information among scientific 

 and practical men by means of periodical publications. Op- 

 portunities are offered of putting I'acts upon record without 

 difficulty or delay; and although some communications may 

 possess a greater degree of interest than others, yet there is 

 probably no one in which well-ascertained facts are correctly 

 stated, which remains without its use at some period or other. 

 I am induced by these considerations to send you an account 

 of two experiments which I lately made on the reduction of 

 galena. 



Experiment 1. — An earthen tube 18 inches long and |ths of 

 an inch internal diameter was properly coated, and made to 

 traverse a furnace in which ten inches of the middle could be 

 highly heated. To one end was attachetl a bent tube ter- 

 minating in a pneumatic trough, and to the otlier a retort 

 containing water made to boil by the flame of a lamj). One 

 thousand grains of very pure cubical galena were wrajiped u\> 

 in a cylinder of jjapei', and pushed to the middle of the tube 

 when very hot; and over this was transmitted a current of 

 steam, A copious stream of sulphuretted hydrogen gas was 

 emitted, and the water in the pneumatic trough became as 

 white as milk, before the operation was concluded: no preci- 

 pitate was deposited from this water after standing t\\enty-four 

 hours, it was still milky and turbid. The process was con- 

 tiiuied an hour; and during the whole time gas of the same 

 kind was given off", but slowly towards the conclusion. 



On breaking the tube after cooling, it exhibited the follow- 

 ing appearances. 



d. A cake of fused and partly reduced galena, flat on the 

 upper surface, and having the form of the tube below, occu- 

 pied three inches of the tube nearest the retort from which the 

 steam issued. This mass was brittle; it could be cut with a 

 knife, but not a particle of metallic leail was observable. This 

 substance was most probably a sub-sulphuret of lead. 



h. Six 



