308 0. Barus — Resolution of Interference Fringes. 



Art. XXYII. — The Resolution of Interference Fringes ; by 



C. Bartjs. 



1. Experiment. — The following remarks apply to interfer- 

 ence fringes produced preferably by the bi-prism, though 

 Young's slits and the other methods of course show the same 

 results. The experiment is straightforward, as is given in 

 fig. 1, but the effect obtained is at first quite unexpected. 



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In fig. 1 the arc light A passing the condenser G and the 

 slit S, falls on the bi-prism B and then upon the direct vision 

 spectroscope & G ( preferably of the grating form like that of 

 Mr. Ives), where S' is the slit, G the grating with attached 

 prism, L and L' the collimator and eyepiece, respectively. 

 Both slits S and S' must be as fine as possible, the spectrum 



