20 i)R. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XVIII.) 
more or less the contact and subsequent separation of the particles of water and the 
solid substance against which they rub. 
2088. When the mixed steam and water pass through a tube or stop-cock (2076.), 
they may issue, producing either a hissing smooth sound, or a rattling rough sound* ; 
and with the cone apparatus (2077- fig'- 2.), or certain lengths of tube, these conditions 
alternate suddenly. With the smooth sound little or no electricity is produced ; with 
the rattling sound plenty. The rattling sound accompanies that irregular rough 
vibration, which casts the water more violently and effectually against the substance 
of the passage, and which again causes the better excitation. I converted the end 
of the passage into a steam-whistle, but this did no good. 
2089. If there be no water in the steam-globe (2076.), upon opening the steam- 
cock the first ejfict is very striking ; a good excitement of electricity takes place, 
but it very soon ceases. This is due to water condensed in the cold passages, pro- 
ducing excitement by rubbing against them. Thus, if the passage be a stop-cock, 
whilst cold it excites electricity with what is supposed to be steam only ; but as soon 
as it is hot, the electricity ceases to be evolved. If, then, whilst the steam is issuing, 
the cock be cooled by an insulated jet of water, it resumes its power. If, on the 
other hand, it be made hot by a spirit-lamp before the steam be let on, then there is 
no first effect. On this principle, I have made an exciting passage by surrounding 
one part of an exit tube with a little cistern, and putting spirits of wine or water 
into it. 
2090. We find then that particles of water rubbed against other bodies by a cur- 
rent of steam evolve electricity. For this purpose, however, it is not merely water 
but pure water which must be used. On employing the feeding apparatus (2078.), 
which supplied the rubbing water to the interior of the steam passage, I found, as 
before said, that with steam only I obtained no electricity (2084.). On letting in di- 
stilled water, abundance of electricity was evolved ; on putting' a small crystal of 
sulphate of soda, or of common salt into the water, the evolution ceased entirely. 
Re-employing distilled water, the electricity appeared again ; on using the common 
water supplied to London, it was unable to produce it. 
2091. Again, using the steam-globe (2076.), and a box-wood tube (2102.) which 
excites well if the water distilling over from the boiler be allowed to pass with the 
steam, when I put a small crystal of sulphate of soda, of common salt, or of nitre, or 
the smallest drop of sulphuric acid, into the steam-globe with the water, the appara- 
tus was utterly ineffective, and no electricity could be produced. On withdrawing 
such water and replacing it by distilled water, the excitement was again excellent : 
on adding a very small portion of any of these substances, it ceased ; but upon again 
introducing pure water it was renewed. 
* Messrs. Armstrong and Schafhaeutl have both observed the coincidence of certain sounds or noises with 
the evolution of the electricity. 
