1224.  Some results obtained with a brass hemisphere instead of the ball B were exceedingly interesting, It was 1.36 of an inch in diameter, (fig. 110.), and being placed on the top of the excited shell-lac cylinder, the carrier ball was applied, as in the former experiments (1218.), at the respective positions delineated in the figure.  At i the force was 112 deg., at k 108 deg., at l 65 deg., at m 35 deg.; the inductive force gradually diminishing, as might have been expected, to this point.  But on raising the carrier to the position n, the charge increased to 87 deg.; and on raising it still higher to o, the charge still further increased to 105 deg.:  at a higher point still, p, the charge taken was smaller in amount, being 98 deg., and continued to diminish for more elevated positions.  Here the induction fairly turned a corner.  Nothing, in fact, can better show both the curved lines or courses of the inductive action, disturbed as they are from their rectilineal form by the shape, position, and condition of the metallic hemisphere; and also a lateral tension, so to speak, of these lines on one another:—­all depending, as I conceive, on induction being an action of the contiguous particles of the dielectric, which being thrown into a state of polarity and tension, are in mutual relation by their forces in all directions.

1225.  As another proof that the whole of these actions were inductive I may state a result which was exactly what might be expected, namely, that if uninsulated conducting matter was brought round and near to the excited shell-lac stem, then the inductive force was directed towards it, and could not be found on the top of the hemisphere.  Removing this matter the lines of force resumed their former direction.  The experiment affords proofs of the lateral tension of these lines, and supplies a warning to remove such matter in repeating the above investigation.

1226.  After these results on curved inductive action in air I extended the experiments to other gases, using first carbonic acid and then hydrogen:  the phenomena were precisely those already described.  In these experiments I found that if the gases were confined in vessels they required to be very large, for whether of glass or earthenware, the conducting power of such materials is so great that the induction of the excited shell-lac cylinder towards them is as much as if they were metal; and if the vessels be small, so great a portion of the inductive force is determined towards them that the lateral tension or mutual repulsion of the lines of force before spoken of, (1224.) by which their inflexion is caused, is so much relieved in other directions, that no inductive charge will be given to the carrier ball in the positions k, l, m, n, o, p (fig. 110.).  A very good mode of making the experiment is to let large currents of the gases ascend or descend through the air, and carry on the experiments in these currents.