1310.  On employing a plate of sulphur instead of shell-lac, the same results were obtained; consistent with the conclusions drawn regarding the high specific inductive capacity of that body already given (1276.).

1311.  These effects of specific inductive capacity can be exalted in various ways, and it is this capability which makes the great value of the apparatus.  Thus I introduced the shell-lac between A and B, and then for a moment connected B and C, uninsulated them, and finally left them in the insulated state; the gold leaves were of course hanging parallel to each other.  On removing the shell-lac the gold leaves attracted each other; on introducing the shell-lac between A and C this attraction was increased, (as had been anticipated from theory,) and the leaves came together, though not more than four inches long, and hanging three inches apart.

1312.  By simply bringing the gold leaves nearer to each other I was able to show the difference of specific inductive capacity when only thin plates of shell-lac were used, the rest of the dielectric space being filled with air.  By bringing B and C nearer to A another great increase of sensibility was made.  By enlarging the size of the plates still further power was gained.  By diminishing the extent of the wires, &c. connected with the gold leaves, another improvement resulted.  So that in fact the gold leaves became, in this manner, as delicate a test of specific inductive action as they are, in Bennet’s and Singer’s electrometers, of ordinary electrical charge.

1313.  It is evident that by making the three plates the sides of cells, with proper precautions as regards insulation, &c., this apparatus may be used in the examination of gases, with far more effect than the former apparatus (1187. 1290), and may, perhaps, bring out differences which have as yet escaped me (1292. 1293.)

1314.  It is also evident that two metal plates are quite sufficient to form the instrument; the state of the single inducteous plate when the dielectric is changed, being examined either by bringing a body excited in a known manner towards its gold leaves, or, what I think will be better, employing a carrier ball in place of the leaf, and examining that ball by the Coulomb electrometer (1180.).  The inductive and inducteous surfaces may even be balls; the latter being itself the carrier ball of the Coulomb’s electrometer (1181. 1229.).

1315.  To increase the effect, a small condenser may be used with great advantage.  Thus if, when two inducteous plates are used, a little condenser were put in the place of the gold leaves, I have no doubt the three principal plates might be reduced to an inch or even half an inch in diameter.  Even the gold leaves act to each other for the time as the plates of a condenser.  If only two plates were used, by the proper application of the condenser the same reduction might take place.  This expectation is fully justified by an effect already observed and described (1229.).