JTol. 35. MAY 1868. No. 238. 



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THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE, 



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JOURNAL OF SCIENCE. 



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 Nicholson's 'Journal/ and Thomson's ( Annals of Philosophy. 9 



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FOURTH SERIES. 



N° 238.— MAY 1868. 



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