The Ultraviolet Spectra of 17 Leporis and P Cygni.

The ultraviolet spectrum of i 7 Leporis is compared with that of a Cygni. Ti rr, Sc ii, and Mn ii are greatly enhanced fri 17 Leporis. Si ii is abnormally weak. From the relative intensities of three Mg i lines it is found that the dilution factor W > ~ Other estimates suggest 0.1 > W > 0.01. The observations are, in gen- eral, consistent with the theory of cycles. One hundred and fifteen lines were measured in the spectrum of P Cygni between A 3265 and X 4026. The Balmer series is followed to n = 23. The triplet diffuse series of lie i is found to extend to appreciably higher members than the singlet diffuse series. The 23P level is estimated to be overpopulated by a factor of ~. This could be caused by a dilution factor W = 0.05, which corresponds to R/r = 0.4, where R and r are the radii of the star and of the shell, respectively. The Si Ill triplet, 4p3P° - 4d~D, is found to be in emission in contrast with the well-known triplet 4s3S - 4p3P0, which is in absorption. Several strong lines are due to Fe irr. The effect of dilution in this spectrum is discussed