EXCITATION OF ELECTRICITY BY STEAM AND OTHER SUBSTANCES. 
23 
seen to be still, but if removed the least degree to the right or left of the axis of the 
stream it (very naturally) vibrated, or rather rotated, describing a beautiful circle, of 
which the axis of the stream was the tangent : the interesting point was to observe, 
that when the thread rotated, travelling as it were with the current, there was little 
or no electricity evolved, but that when it was nearly or quite stationary there was 
abundance of electricity, thus illustrating the effect of friction. 
2102. The difference in the quality of the substances above described (2099.) gives 
a valuable power of arrangement at the jet. Thus if a metal, glass, or wood tube* 
(2076.) be used for the steam issue, the boiler is rendered well negative and the steam 
highly positive ; but if a quill tube or, better still, an ivory tube be used, the boiler 
receives scarcely any charge, and the stream of steam is also in a neutral state. This 
result not only assists in proving that the electricity is not due to evaporation, 
but is also very valuable in the experimental inquiry. It was in such a neutral jet 
of steam and water that the excitation of the bodies already described (2099.) was 
obtained. 
2103. Substances, therefore, may be held either in the neutral jet from an ivory 
tube, or in the positive jet from a wooden or metal tube; and in the latter case 
effects occurred which, if not understood, would lead to great confusion. Thus an in- 
sulated wire was held in the stream issuing from a glass or metal tube, about half an 
inch from the mouth of the tube, and was found to be unexcited : on moving it in 
one direction a little further off, it was rendered positive ; on moving it in the other 
direction, nearer to the tube, it was negative. This was simply because, when near 
the tube in the forcible part of the current, it was excited and rendered negative, 
rendering the steam and water more positive than before, but that when further off, 
in a quieter part of the current, it served merely as a discharger to the current pre- 
viously excited in the exit tube, and so showed the same state with it. Platinum, 
copper, string, silk, wood, plumbago, or any of the substances mentioned above 
(2099.), excepting quill, ivory, and bear’s hair, could, in this way, be made to assume 
either one state or the other, according as they were used as exciters or dischargers, 
the difference being determined by their place in the stream. A piece of fine wire 
gauze held across the issuing jet shows the above effect very beautifully; the differ- 
ence of an eighth of an inch either way from the neutral place will change the state 
of the wire gauze. 
2104. If, instead of an excited jet of steam and water (2103.), one issuing from an 
ivory tube (2102.), and in the neutral state be used, then the wires, &c. can no longer 
be made to assume both states. They may be excited and rendered negative (2099.), 
but at no distance can they become dischargers, or show the positive state. 
2105. We have already seen that the presence of a very minute quantity of matter 
able to give conducting power to the water took away all power of excitation (2090, 
* A box-wood tube, 3 inches long and ith of an inch inner diameter, well soaked in distilled water and 
screwed into the steam-globe, is an admirable exciter. 
