A text-book on chemistryFor the use of schools and colleges . vided into two parts. The same body may be causedto become either magnetic or diamagnetic, by changingthe medium by which it is surrounded. Magnetismalso exerts an influence on polarized light transmittedthrough certain transparent bodies. This may be shownby placing them, while under examination, in the mag-netic field. The beam is caused to rotate to an extentwhich depends on the nature of the body and the inten-sity of the magnetism. If a copper cylinder, Fig. 151, filled with fusible metal,be so arranged, \. by the aid ofth
A text-book on chemistryFor the use of schools and colleges . vided into two parts. The same body may be causedto become either magnetic or diamagnetic, by changingthe medium by which it is surrounded. Magnetismalso exerts an influence on polarized light transmittedthrough certain transparent bodies. This may be shownby placing them, while under examination, in the mag-netic field. The beam is caused to rotate to an extentwhich depends on the nature of the body and the inten-sity of the magnetism. If a copper cylinder, Fig. 151, filled with fusible metal,be so arranged, \. by the aid ofthe band S S, asto rotate rapid-ly in the mag-netic field, theresistance to itsmotion is sogreat that it will seem to be grasped by an invisiblehand. On continuing the rotation for a few minutes,the heat developed will be sufficient to melt the con-tained alloy, which may be poured out upon the table. What is the effect on a taper in the magnetic field ? How maythe effect of magnetism be demonstrated by polarized light? De-scribe the experiment, Fig. 151. 112. 178 PROPERTIES OF A HELIX. Fig. 152. LECTURE XXXIII. Electro-Dynamics.—Ampere?s Discovery.—Propertiesof a Helix.— Cause of Magnetism.—Faradays Dis-covery of Magnetic Electricity.—Magnetic Machines.—Ruhmkorjf s Coil.— Geisslers Tubes.—Thermo-electricity.—Production of Electricity by Heat.—Thermo - Electric Piles.—MellonVs Pile and Ther-mometer.—Drapers Improvements in Thermo-Elec-tric Pairs.—Animal Electricity.—The Torpedo. Soon after the relation between electricity and mag-netism was established by Oersted, Ampere discoveredthat there are reactions between the currents them-selves. Two electric currents flowing in the same di-rection attract each other, but two electric currentsflowing in opposite directions repel. Like currentsattract, unlike ones repel. If a conducting wire, a 5, Fig. 152, be bent in the form of a helix, n s,its ends returningtoward its middle,it exhibits all theproperties of
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