THE 



AMERICAN JOURNAL OF SCIENCE 



[ F OURTH SERIES.] 



Art. XIX. — The Transmission of Light through Transparent 

 Inactive Crystal Plates, with Special Reference to Observa- 

 tions in Convergent Polarized Light; by Feed. Eugene 

 Weight. 



Introduction. 



The problem of the refraction and reflection of light on 

 inactive, transparent crystal plates has long attracted the atten- 

 tion of physicists and crystallographers, and has proved a 

 fruitful field of investigation from the standpoints both of 

 theory and of applied physical optics. The general problem 

 was first successfully attacked in 1835 by F. Neumann 1 in Ger- 

 many and by J. MacCullagh 2 in Ireland, Neumann using 

 strictly analytic methods ; MacCullagh, on the other hand, 

 inclining rather to geometric methods and attaining thereby 

 greater simplicity in his treatment of the whole. Both Neu- 

 mann and MacCullagh showed keen mathematical insight and 

 judgment in overcoming the inherent difficulties of this prob- 

 lem ; their work, moreover, was remarkably thorough and 

 comprehensive, and has served as the foundation on which all 

 subsequent investigations have been based. Their general 

 conclusions have remained intact and valid to the present day, 

 even though their methods of calculation have been superseded 

 by simpler and more effective methods and their fundamental 

 assumptions have been modified to some extent and expressed 

 in terms more nearly in accord with modern views on the 

 nature of light. 



1 Theoretische Untersuchungen der Gesetze, nach welchen das Licht an 

 der Grenze zweier vollkoininen durehsichtiger Medien reflektiert und gebro- 

 chen wird. Berliner Akad. Abh. 1835, Math. Abt. p. 1-160 ; also Poggen- 

 dorf's Annalen. xlii, 1-37, 1837. 



2 Phil. Mag. (3), viii, 103, 1835; x, 42, 1837 ; On the Laws of Crystalline 

 Eeflexion and Refraction, Trans. Roy. Irish Acad, xviii, p. 31, 1837 ; Col- 

 lected Works. 1880. 



Am. Jour. Sci. — Fourth Series, Vol. XXXI, No. 183.— March, 1911. 

 12 



