26 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XVIII.) 
effect, I have already referred to (2090, &c.). In addition, I may note that sul- 
phuric ether, pyroxylic spirit, and boracic acid did the same. 
2115. Alcohol seemed at the first moment to render the boiler positive. Half 
alcohol and half water rendered the boiler negative, but much less so than pure 
water. 
2116. It must be considered that a substance having- the reverse power of water, 
but only in a small degree, may be able to indicate that property merely by diminishing 
the power of water. This diminution of power is very different in its cause to that 
dependent on increasing the conducting power of the water, as by saline matter 
(2090.), and yet the apparent effect will be the same. 
211/. When it is required to render the issuing steam permanently negative, the 
object is very easily obtained. A little oil or wax put into the steam-globe (2076.), 
or a thick ring of string or canvas soaked in wax, or solution of resin in alcohol, 
and introduced into the box C (2079.), supplies all that is required. By adjusting 
the application it is easy to neutralize the power of the water, so that the issuing 
stream shall neither become electric, nor cause that to be electrified against which it 
rubs. 
2118. We have arrived, therefore, at three modes of rendering the jet of steam 
and water neutral, namely, the use of an ivory or quill tube (2102.), the presence of 
substances in the water (2090, &c.), and the neutralization of its natural power by 
the contrary force of oil, resin, &c. &c. 
2119. In experiments of the kind just described an ivory tube cannot be used 
safely with acid or alkalies in the steam-globe, for they, by their chemical action on 
the substance of the tube, in the evolution or solution of the oily matter for instance, 
change its state and make its particular power of excitement very variable. Other 
circumstances also powerfully affect it occasionally (2144.). 
2120. A very little oil in the rubbing passages produces a great effect, and this at 
first was a source of considerable annoyance, by the continual occurrence of unex- 
pected results ; a portion may lie concealed for a week together in the thread of an 
unsuspected screw, and yet be sufficient to mar the effect of every arrangement. Di- 
gesting and washing with a little solution of alkali, and avoiding all oiled washers, is 
the best way in delicate experiments of evading the evil. Occasionally I have found 
that a passage, which was in some degree persistently negative, from a little melted 
caoutchouc, or positive from oil, resin, &c., might be cleared out thoroughly by let- 
ting oil of turpentine be blown through it ; it assumed for a while the positive state, 
but when the continuance of steam had removed that (2110.), the passage appeared 
to be perfectly clear and good and in its normal condition. 
2121. I now tried the effect of oil, &c. when a little saline matter or acid was 
added to the water in the steam-globe (2090, &c.), and found that when the water 
was in such a state as to have no power of itself, still oil of turpentine, or oil, or resin 
in the box C, showed their power, in conjunction with such water, of rendering the 
