18 DR, FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XVIII.) 
2077- Another issue piece consisted of a metal tube terminated by a metal funnel, 
and of a cone advancing by a screw more or less into the funnel, so that the steam 
as it rushed forth beat against the cone (Plate I. fig. 2.) ; and this cone could either 
be electrically connected with the funnel and boiler, or be insulated. 
2078. Another terminal piece consisted of a tube, with a stop-cock and feeder at- 
tached to the top part of it, by which any fluid could be admitted into the passage, 
and carried on with the steam (fig. 3.). 
2079. In another terminal piece, a small cylindrical chamber was constructed 
(fig. 4.) into which different fluids could be introduced, so that, when the cocks were 
opened, the steam passing on from the steam-globe (2076.) should then enter this 
chamber and take up anything that was there, and so proceed with it into the final 
passage, or out against the cone (2077-)? according as the apparatus had been com- 
bined together. This little chamber I will always call C. 
2080. The pressure at which I worked with the steam was from eight to thirteen 
inches of mercury, never higher than thirteen inches, or about two-fifths of an atmo- 
sphere. 
2081. The boiler was insulated on three small blocks of lac, the chimney being con- 
nected by a piece of funnel-pipe removable at pleasure. Coke and charcoal were burnt, 
and the insulation was so good, that when the boiler was attached to a gold-leaf elec- 
trometer and charged purposely, the divergence of the leaves did not alter either by the 
presence of a large fire, or the abundant escape of the results of the combustion. 
2082. When the issuing steam produces electricity, there are two ways of exami- 
ning the effect : either the insulated boiler may be observed, or the steam may be ex- 
amined, but these states are always contrary one to the other. I attached to the 
boiler both a gold-leaf and a discharging electrometer, the first showed any charge 
short of a spark, and the second by the number of sparks in a given time carried 
on the measurement of the electricity evolved. The state of the steam may be ob- 
served either by sending it through an insulated wide tube in which are some dia- 
phragms of wire gauze, which serves as a discharger to the steam, or by sending a 
puff of it near an electrometer when it acts by induction ; or by putting wires and 
plates of conducting matter in its course, and so discharging it. To examine the 
state of the boiler or substance against which the steam is excited, is far more con- 
venient, as Mr. Armstrong has observed, than to go for the electricity to the steam 
itself ; and in this paper I shall give the state of the former, unless it be otherwise 
expressed. 
2083. Proceeding to the cause of the excitation, I may state first that I have satis- 
fied myself it is not due to evaporation or condensation, nor is it affected by either 
the one or the other. When the steam was at its full pressure, if the valve were 
suddenly raised and taken out, no electricity was produced in the boiler, though the 
evaporation was for the time very great. Again, if the boiler were charged by excited 
