_Apparatus._ Same as in last experiment, but arrange so that F B and I T shall be near each other at one side; that is, so that the edge of E S shall be even with the edges of the two tins. =183. Directions.= (A) Pass good sparks to I T from the charged E C until something happens. Watch the side where I T and F B are near each other. _=184. Discussion.=_ We may say that the electrification was condensed, in this experiment, until the charge became so great that the _condenser_ suddenly discharged itself. Condensers may be made in many ways, but they all consist of 2 conductors, with a dielectric between them. One conductor is insulated, and receives the charge; the other conductor is grounded. [Illustration: Fig. 53.] =EXPERIMENT 85. To study the action of the condenser.= _Apparatus._ Fig. 53. The insulating table, I T; ebonite sheet, E S (No. 27); flat box, F B, complete (Nos. 40, 41); the electrophorus (Exp. 68). Note that this is really the same apparatus as that just used; both conductors of this condenser, however, are insulated and reversed in position. =185. Directions.= (A) See that your electrophorus works properly, then find out how many good sparks you can pass from E C to F B, recharging E C each time. Note the relative sizes of the sparks, and compare the result with the number taken by the condenser in the last experiment. (B) When F B seems to be fully charged, touch I T with your knuckle. (From your study of induction what should be the result?) (C) Now see if F B will again take good sparks from the charged E C. Pass sparks to F B until it seems fully charged. (D) Again touch I T, then repeat (A) and (B) several times, until a bright spark passes from F B over the edge of E S to I T. _=186. Discussion.=_ The action of the condenser, as clearly shown, depends upon induction. You should now be able to explain and show by diagram the different steps.