=Note.= You have seen that we can _pound_ magnetism into or out of a piece of iron at will. Can we _twist_ it into a wire and out again without the use of magnets?
=94. Directions.= (A) Test the wire for poles with O C.
(B) Hold the wire in a N and S direction, dipping it at the same time, as directed in Exp. 47 for the poker, and twist it back and forth.
(C) Test again for poles with O C. As the poles of the wire may be very weak, bring them _slowly_ toward the compass-needle (see Exp. 14), and note the _first_ motions produced upon the needle.
(D) Hold the wire horizontally east and west, twist and test again. Has its magnetism become weaker or stronger than before?
=EXPERIMENT 50. To test for magnetism in bars of iron, tools, etc.=
_Apparatus._ Steel drills; files; chisels; bars or rods of iron that have been standing in an upright position; stove-lid lifters; stove pokers, etc., etc.; a compass.
=95. Directions.= (A) With the compass test the ends of the above for magnetism, and note which ends are S.
_=100. Some Varieties of Electricity.=_ _Static electricity_ does not seem to "flow in currents" as readily as some other varieties; its tendency is to stand still, hence the name, static. The simplest way to produce it is by friction. _Thermo electricity_ is produced by changes in temperature. When certain combinations of metals become hotter or colder, a current is produced. _Voltaic_ or _Galvanic electricity_ is produced by chemical action. Batteries give this variety. _Induced electricity_ is produced by other currents, and by combinations of magnets and moving coils of wire, as in the dynamo. This is, by far, the most important variety of electricity, and the dynamo is the most important producer of it.
Each of the above varieties of electricity will be studied experimentally with simple apparatus.
=EXPERIMENTS 51-52.= To study electrification by friction.
_Apparatus._ Ebonite sheet, E S (No. 26); flannel cloth, F C (No. 30). See what is said in preface about static electricity.
=101. Directions.= (A) Examine E S. Note that its surface is not smooth, like that of ordinary hard-rubber combs. Can you think of any reason for this?
(B) Hold its flat surface near your face, then near the back of your hand. Do you feel anything unusual?