1227.  These experiments were then varied by the substitution of a liquid dielectric, namely, oil of turpentine, in place of air and gases.  A dish of thin glass well-covered with a film of shell-lac (1272.), which was found by trial to insulate well, had some highly rectified oil of turpentine put into it to the depth of half an inch, and being then placed upon the top of the brass hemisphere (fig. 110.), observations were made with the carrier ball as before (1224.).  The results were the same, and the circumstance of some of the positions being within the fluid and some without, made no sensible difference.

1228.  Lastly, I used a few solid dielectrics for the same purpose, and with the same results.  These were shell-lac, sulphur, fused and cast borate of lead, flint glass well-covered with a film of lac, and spermaceti.  The following was the form of experiment with sulphur, and all were of the same kind.  A square plate of the substance, two inches in extent and 0.6 of an inch in thickness, was cast with a small hole or depression in the middle of one surface to receive the carrier ball.  This was placed upon the surface of the metal hemisphere (fig. 112.) arranged on the excited lac as in former cases, and observations were made at n, o, p, and q.  Great care was required in these experiments to free the sulphur or other solid substance from any charge it might previously have received.  This was done by breathing and wiping (1203.), and the substance being found free from all electrical excitement, was then used in the experiment; after which it was removed and again examined, to ascertain that it had received no charge, but had acted really as a dielectric.  With all these precautions the results were the same:  and it is thus very satisfactory to obtain the curved inductive action through solid bodies, as any possible effect from the translation of charged particles in fluids or gases, which some persons might imagine to be the case, is here entirely negatived.

1229.  In these experiments with solid dielectrics, the degree of charge assumed by the carrier ball at the situations n, o, p (fig. 112.), was decidedly greater than that given to the ball at the same places when air only intervened between it and the metal hemisphere.  This effect is consistent with what will hereafter be found to be the respective relations of these bodies, as to their power of facilitating induction through them (1269. 1273. 1277.).

1230.  I might quote many other forms of experiment, some old and some new, in which induction in curved or contorted lines takes place, but think it unnecessary after the preceding results; I shall therefore mention but two.  If a conductor A, (fig. 111.) be electrified, and an uninsulated metallic ball B, or even a plate, provided the edges be not too thin, be held before it, a small electrometer at c or at d, uninsulated, will give signs of electricity, opposite in its nature to that