22 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XVIII.) 
time the oil of turpentine, olive-oil and resin were found cleared off from the parts 
struck by the stream of steam and water. A cone of kerseymere, which had been 
dipped in alcoholic solution of resin and dried two or three times in succession, was 
very irregular, becoming positive and negative by turns, in a manner difficult to 
comprehend at first, but easy to be understood hereafter (2113.). 
2098. The end of a rod of shell-lac was held a moment in the stream of steam and 
then brought near a gold-leaf electrometer: it was found excited negative, exactly as 
if it had been rubbed with a piece of flannel. The corner of a plate of sulphur 
showed the same effect and state when examined in the same way. 
2099. Another mode of examining the substance rubbed was to use it in the shape 
of wires, threads or fragments, holding them by an insulating handle in the jet, whilst 
they were connected with a gold-leaf electrometer. In this way the following sub- 
stances were tried : — 
Horse-hair, 
Bear’s hair, 
Flint glass, 
Green glass, 
Quill, 
Ivory, 
Shell-lac on silk, 
Sulphur on silk, 
Sulphur in piece, 
Plumbago, 
All these substances were rendered negative, though not in the same degree. This 
apparent difference in degree did not depend only upon the specific tendency to 
become negative, but also upon the conducting power of the body itself, whereby it 
gave its charge to the electrometer ; upon its tendency to become wet (which is very 
different, for instance in shell-lac or quill, to that of glass or linen), by which its con- 
ducting quality was affected ; and upon its size or shape. Nevertheless I could di- 
stinguish that bear’s hair, quill and ivory had very feeble powers of exciting electri- 
city as compared to the other bodies. 
2100. I may make here a remark or two upon the introduction of bodies into the 
jet. For the purpose of preventing condensation on the substance, I made a platinum 
wire white-hot by an insulated voltaic battery, and introduced it into the jet : it was 
quickly lowered in temperature by the stream of steam and water to 212°, but of 
course could never be below the boiling point. No difference was visible between 
the effect at the first instant of introduction or any other time. It was always in- 
stantly electrified and negative. 
2101. The threads I used were stretched across a fork of stiff wire, and the middle 
part of the thread was held in the jet of vapour. In- this case, the string or thread, 
if held exactly in the middle of the jet and looked at end-ways to the thread, was 
Platinum, 
Copper, 
Iron, 
Zinc, 
Sulphuret of copper, 
Linen, 
Cotton, 
Silk, 
Worsted, 
Wood, 
Charcoal, 
Asbestus, 
Cyanite, 
Haematite, 
Rock-crystal, 
Orpiment, 
Sulphate of baryta. 
Sulphate of lime. 
Carbonate of lime, 
Fluor-spar. 
