_=206. Discussion.=_ The permanent divergence of L was due to a charge given by induction. (Exp. 76.) As E S was -, what was the kind of a charge in L? Did any electrification go to the electroscope from E S? In (C) what became of the charge in L? Explain why the leaves again diverged in (D). The electroscope was charged with + electrification by taking - out of it. =EXPERIMENT 95. To learn some uses of the electroscope.= _Apparatus._ Our electroscope (Fig. 57, § 202); ebonite rod, E R (No. 28); ebonite sheet, E S (No. 27); glass, G (No. 38); flannel cloth, F C (No. 30). =207. Directions.= (A) With the charged E R charge the electroscope negatively by conduction (Exp. 93). Note the amount of permanent divergence of the leaves. (B) Electrify the glass, which will be +, (or use the + E C), and _slowly_ lower it over I T, noting the effect upon L. Raise and lower G or E C several times. Does G, which has an opposite charge to the electroscope, make L diverge more or less? (C) Discharge the electroscope and recharge as in (A). (D) Slowly lower the charged E S over I T. (E) Slowly lower the palm of your hand over I T. =Note.= If the + G is brought too near the -ly charged electroscope, L will first collapse and then instantly diverge again with a + charge by contact. The _first_ motions should be observed. _=208. Discussion.=_ As a neutral body causes a slight _collapse_ of the leaves, as well as a body charged positively (when the charge in the leaves is -), an increase of divergence is really the only sure test to tell how a body is charged. The - leaves collapse when a + body is brought near I T, because the - in them is drawn up towards the body. The leaves diverge more when a - body is brought near, because the - in I T is repelled into them. _=209. The Proof-plane.=_ Since charges of static electricity reside upon the outside of conductors, it is an easy matter to take samples of the electrification. This may be done with a little instrument called a carrier, or proof-plane. It consists of a small conductor with an insulating handle. A ring or coin may be used for the conductor, and a silk thread for the handle. By touching the carrier to any charged body, it, also, becomes charged; and the nature of the charge may be determined by the use of a previously charged leaf electroscope (Exp. 95). A delicate gold-leaf electroscope would be ruined by coming in contact with a heavily charged body. The carrier allows a small sample to be tested. CHAPTER XII. MISCELLANEOUS EXPERIMENTS. [Illustration: Fig. 58.] =EXPERIMENT 96. To show that friction always produces two kinds of electrifications.= _Apparatus._ Fig. 58. The carbon electroscope (Exp. 58); flannel cloth, F C, doubled twice to make 4 thicknesses (see Fig. 58); ebonite sheet, E S (No. 26); ebonite rod, E R (No. 28); charged electrophorus cover, E C.