E C was positively charged (Exp. 80). This also charged F B positively by contact. F B acted inductively through the dielectric, E S, drawing up _some_ of the - in I T, and repelling _some_ of the +. As I T was insulated, this free + electrification could not escape. Before we touched I T, its + and - electrifications, although partially separated, were struggling against this inductive action; and, on account of their strong attraction for each other, our efforts to charge the condenser were retarded. Upon touching I T the free + escaped to the earth. (This was the cause of the spark.) This left _some_ - electrification bound on the underside of E S, and some + bound on the upperside of E S. The capacity of F B was increased by this process, as the + already put into it was very much occupied by the attractions of the induced - just under E S. As more + was given to F B, more - was drawn up under E S and more + was pushed out of I T. This action went on until the two conductors were strongly and oppositely charged. This action goes on continuously when the lower conductor is grounded. The spark between the tins was due to the rushing together of the + and - electrifications; it showed that there was a _momentary current of electricity_. =EXPERIMENT 86. To study the effect of electrical discharges upon the human body.= _Apparatus._ The condenser (Fig. 52), with E S centrally placed so that the apparatus cannot discharge itself; the hairpin discharger, H P D (No. 48); the electrophorus. =187. Directions.= (A) Charge the condenser (Exp. 83) with 10 good sparks from E C, then touch I T (Fig. 52). (B) Recharge the condenser with 10 sparks, then touch F B. Discharge it by again touching I T as in (A). (C) Recharge with 10 sparks; then place your thumb against F B, and quickly swing the first finger of the same hand over to I T, and get a slight shock. (D) Recharge with as many sparks as you think you can stand. (E) Instead of using your hand to discharge the condenser, try the bent hairpin. Keeping one end against F B, swing the other end over near I T. _=188. Shocks; Dischargers.=_ The two conductors being oppositely charged in the condenser (Exp. 85), it is only necessary to place some conductor between them to allow the charges to rush together. Any conductor so used is called a _discharger_. The hand carried the whole current which caused the _shock_. When I T was touched first, the current was obliged to pass through your body, through the floor, and up the table-legs into F B. Always touch the "grounded" conductor first with the discharger, so that you will get a good spark and _not_ a shock. =EXPERIMENTS 87-88. To show the strong attraction between the opposite electrifications in the condenser.=