94 Mr. John Williams on the Electricity of Steam. 



"With a view to find out the cause of volcanic lightning, I 

 made some experiments with great care, by insulating a small 

 portable furnace ; and by doubling the electrical signs, by 

 means of condensers, I found the insulated furnace to be in 

 a negative state when the fire burnt with a strong flame ; 

 these electrical signs, however, were strongest after the ad- 

 dition of fresh fuel, and when a deiise smoke arose a few seconds 

 before it burnt intofame'^-. 



After the locomotive high-pressure engines came into use 

 as yiublic conveyances for passengers, I visited Manchester and 

 Liverpool purposely to inspect the machinery and observe the 

 steam- and hot-air cloud when issuing from the funnel ; the 

 weather being cold, and consequently the steam visible, I no- 

 ticed the rapid divergence of the particles of vapour, and thought 

 this might be caused by its electrical state, which I resolved to 

 prove by experiment, but which I was not enabled to do till 

 November 1838, when, having provided myself with a small 

 close-covered boiler, made with strong sheet-copper, and fur- 

 nished with a safety valve loaded with a weight, it was placed 

 on a portable furnace, and insulated on a stool with glass legs, 

 placed under a large spreading willow-tree in my garden, 

 where I never could observe any signs of atmospherical elec- 

 tricity. The day was nearly calm. The following is a copy 

 of the marginal note I entered in my meteorological journal : 



" November 13di, 1838. — To-day I repeated a former ex- 

 perimentfj which fully confirmed my pre-conceived ideas, that 

 when steam, confined under pressure in a boiler, is suddenly 

 allowed to escape into the open air, the liberated steam has 

 its capacity for electricity increased, consequently it leaves an 

 insulated boiler in a negative state, which proved to be the 

 case ; for on raising the safety valve by means of a silk string 

 and a piece of sealing-wax, the gold leaves of the electrometer 

 opened one quarter of an inch with negative electricity." 

 I am, Gentlemen, 



Your obedient servant, 



Pitmaston, Worcester, 15th December, 1840. JoHN WiLLIAMS, 



* [It must be remembered, that the cloud, appaientlj' of smoke, which 

 issues from the crater of a volcano in eruption, is not really smoke, but 

 steam, (mingled with finely-divided solid matter — volcanic sand, — consist- 

 in" almost entirely of di-electrics,) issuing from an orifice in non-conduct- 

 ing matter. Volcanic lightning, therefore, is precisely analogous to the 

 electric sparks given by effluent steam. — E. W. B.] 



t The former experiment here alluded to was made by me many years 

 ago, by opening a steam-cock on a large Watt's low-pressure engine boiler, 

 and I found by my electrometer that the expanding steam-cloud was in a 

 state oi positive electricity. 



