CONTENTS 



CHAPTER 



XXIV. 



XXV. 



XXVI. 



XXVII. 



XXVIII. 



XXIX. 



XXX. 



XXXI. 



XXXII. 



XXXIII. 



XXXIV. 



XXXV. 



INDEX 



CHEMICALS AS DISINFECTANTS AND PRESERVATIVES 

 DRUGS AND PATENT MEDICINES .... 

 NITROGEN AND ITS RELATION TO PLANTS . 



SOUND 



MUSICAL INSTRUMENTS 



SPEAKING AND HEARING . . . . 



ELECTRICITY 



SOME USES OF ELECTRICITY .... 



MODERN ELECTRICAL INVENTIONS 



MAGNETS AND CURRENTS .... 



How ELECTRICITY MAY BE MEASURED 



How ELECTRICITY is MADE ON A LARGE SCALE 



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255 

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339 

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353 



