(B) Charge E S, and bring it slowly near one side of the charged end of E R. =EXPERIMENT 57. To study electrical repulsions.= _Apparatus._ A sheet of tissue-paper, T P (No. 31); shears or a knife. Cut T P, as in Fig. 30. Each leg should be about 1/4 in. wide and 3 or 4 in. long. =113. Directions.= (A) Heat the paper, then place it flat upon the table and electrify it by rubbing it with your hand. You must rub away from the uncut part, or you will break the legs. (B) Raise T P, holding it by the uncut part. Note the action of legs, and make a sketch of them. [Illustration: Fig. 30.] [Illustration: Fig. 31.] =EXPERIMENT 58. To study electrical repulsions.= _Apparatus._ Ebonite rod, E R (No. 28); a carbon electroscope, C E, Fig. 31 (see § 114); the support complete (see § 109); small piece of damp tissue-paper. _=114. The Carbon Electroscope.=_ Light an ordinary match, and let it burn until it is charred through and through. The black substance remaining is _carbon_. This is very light; it has, also, another important property which you will soon understand. Tie a small piece of the carbon to one end of a dry _silk_ thread, and fasten the other end of the thread to the support wire, S W, which is fastened to the support (Fig. 31). We shall call this piece of apparatus the _carbon e-lec-tro-scope_. (See Electroscopes, Chapter XVIII., Apparatus Book.) =115. Directions.= (A) Electrify E R, then hold it near the carbon of the electroscope. (B) Bring the charged rod near little pieces of _damp_ tissue-paper. _=116. Discussion of Experiments 56, 57, 58.=_ In 56 the two pieces of ebonite were made of the same material, and both were rubbed with flannel. They must have been similarly electrified. In 57, different parts of the same piece of paper were similarly electrified. In 58, the little piece of carbon took some of the electrification from the charged rod, just as it would take molasses from your finger should your sticky finger touch it. The electrification on the carbon must have been of the same kind as that on the rod. The carbon was _charged by contact_. We learn, then, that _two bodies repel each other when they have the same kind of electrification_. Do two charged bodies _always_ repel each other? Is it possible that there are different kinds of electrifications? =EXPERIMENT 59. To study the electrification of glass.= _Apparatus._ The sheet of glass, G (No. 38), heated (a hot bottle or lamp chimney will do); a piece of silk large enough to rub G. (A silk handkerchief is just the thing, but in case you have no silk, use the flannel cloth, F C, No. 30.) =117. Directions.= (A) Vigorously rub the hot glass with the silk (or flannel), also heated. (B) Test G for electrification by means of little pieces of tissue-paper and the carbon electroscope, Exp. 58.