iv 



SCIENCE.- ADVERTISEMENTS. 



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Ninth Itevised Edition. Published Jan. WOL. 



The Microscope and Microscopical Methods 



By SIMON HENRY QAQE, o< Cornell University. 



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Modern Theory of 

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RADIO-ACTIVITY, 

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By AUGUSTO RIGHI 



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Authorized Translation by 



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Professor of Mathematical Physics in 

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