24 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XVIII.) 
&c.) up to the highest degree of pressure, i. e. of mechanical friction that I used 
(2086.) ; and the next point was to ascertain whether it would be so for all the bodies 
rubbed by the stream, or whether differences in degree would begin to manifest them- 
selves. I therefore tried all these bodies again, at one time adding about two grains 
of sulphate of soda to the four ounces of water which the steam-globe retained as a 
constant quantity when in regular action, and at another time adding not a fourth of 
this quantity of sulphuric acid (2091.). In both cases all the substances (2099.) 
remained entirely unexcited and neutral. Very probably, great increase of pressure 
might have developed some effect (2086.). 
2106. With dilute sulphuric acid in the steam-globe, varying from extreme weak- 
ness to considerable sourness, I used tubes and cones of zinc, but could obtain no 
trace of electricity. Chemical action, therefore, appears to have nothing to do with 
the excitement of electricity by a current of steam. 
2107- Having thus given the result of the friction of the steam and water against 
so many bodies, I may here point out the remarkable circumstance of water being 
positive to them all. It very probably will find its place above all other substances, 
even cat’s hair and oxalate of lime (2131.). We shall find hereafter, that we have 
power, not merely to prevent the jet of steam and water from becoming positive, as 
by using an ivory tube (2102.), but also of reducing its own power when passing 
through or against such substances as wood, metal, glass, &c. Whether, with a jet 
so reduced, we shall still find amongst the bodies above mentioned (2099.) some that 
can render the stream positive and others that can make it negative, is a question 
yet to be answered. 
2108. Advancing in the investigation, a new point was to ascertain what other 
bodies, than water, would do if their particles were carried forward by the current of 
steam. For this purpose the feeding apparatus (2078.) was mounted and charged 
with oil of turpentine, to be let in at pleasure to the steam-exit passage. At first the 
feeder stop-cock was shut, and the issuing steam and water made the boiler negative. 
On letting down the oil of turpentine, this state was instantly changed, the boiler be- 
came powerfully positive, and the jet of steam, &c. as strongly negative. Shutting 
off the oil of turpentine, this state gradually fell, and in half a minute the boiler was 
negative, as at first. The introduction of more oil of turpentine instantly changed 
this to positive, and so on with perfect command of the phenomena. 
2109. Removing the feeder apparatus and using only the steam-globe and a wooden 
exit tube (2076.), the same beautiful result was obtained. With pure water in the 
globe the boiler was negative, and the issuing steam, &c. positive ; but a drop or two 
of oil of turpentine, introduced into the steam-globe with the water, instantly made 
the boiler positive and the issuing stream negative. On using the little interposed 
chamber C (2079.), the effects were equally decided. A piece of clean new sail-cloth 
