Mr. John Williams on the Electricity of Steam. 93 



order to ascertain the amount of copper contained in the cop- 

 per ore examined. 100 grains of pure malachite were ex- 

 amined in this manner, and gave equal to 57'5 of pure copper, 

 which is very nearly the quantity that should be obtained ; 

 had the quantity of copper dissolved proved considerably less, 

 it would have shown that the malachite was not in a state of 

 purity. 



XVII. On the Electricifij of Steam. By John Williams, Esq. 

 To the Editors of the mioso-phical Magazine and Journal. 

 Gentlemen, 



EARLY in November last, I read in j'our Journal a com- 

 munication from Mr. Armstrong, of Newcastle-upon- 

 Tyne, on the subject of the electricity observed in a jet of 

 steam issuing from the boiler of a high-pressure steam engine*. 

 I felt much interested on reading this account, as I doubt not 

 that it will eventually lead to some valuable discoveries relative 

 to meteorology and atmospherical electricity, subjects which 

 have occupied much of my attention for more than forty years 

 past. 



Volta's experiment of dropping a red-hot coal into a vessel 

 of water placed on the insulated cap of an electrometer, was 

 repeated by me in various ways and on a large scale ; and 

 from the results, I came to a conclusion that the positive elec- 

 tricity observed in the steam-cloud on its immediate formation 

 was simply the eflect of evaporation, and not, as some elec- 

 tricians have supposed, of a decomposition of the water into 

 its primitive elements. And I imagine, that when steam under 

 great pressure, and, consequently, of a high temperature, is 

 liberated, and in the act of expanding and mixing with atmo- 

 spheric air, ithas its capacity for electricity increased ; and that 

 a similar process is continually in action in the ordinary course 

 of evaporation from the surfaces of water, leaves of vegetables, 

 and moist soil, with this difference; that in the latter natural 

 processes the resulting electricity of the rising vapour is of 

 low intensity, and not discoverable by our ordinary electro- 

 meters. 



These reflections led me to the consideration of the cause 

 of volcanic lightning, and ]iarticularly of the shape generally 

 assumed by the enormous cloud of smoke, as described by Sir 

 William Hamilton on viewing an eruption of Vesuvius. 



• [Papers on this subject have appeared in our Numbers for November, 

 December, and .January; vol. xvii. |). 3/0, 'Slh, 449, 452, and 457; pre- 

 sent yylumc, p. H, 50, and 1)5.— Eurr.] 



