1 14 MEMOIliS OV THE NATIONAL ACADEMY OF SCIENCES. 



have been a very eft'ective apparatus had the telescope iustead of the slit been movable ; but, as 

 the observer tells us that with his adjustment " the center of the slit was far from coinciding 

 with the axis of the telescope," the ettective aperture may have been much less, lie saw 1474 K 

 and traced it to a distance of 22' ± 5' from the moon's limb. 



1874. 



Stone (p. 475). It is especially to be regretted that this obser\'er fails to give the constants 

 of his instrument, not only on account of the value of his observations, but because he was the 

 only spectroscopic observer of this eclii^se. He saw the hydrogen spectrum with 1474 K bright on 

 a continuous s])ectrum in the inner corona, and traced the last-named line in the outer corona to a 

 distance of more than 1° from the moon. He also detected dark lines in the siiectrum of the outer 

 corona, though they were seen with great dififlculty. 



1875. 



Nothing of the siiectroscopic nature of the corona was learned at this eclipse. 



1878. 



Professor Brackett (Amer. Jour. Sci., vol. xvi, p. 287) used a very efiBcient prismatic telescope, 

 but failed to recognize otlii r than a continuous spectrum of the corona. Other observers with 

 prisms or gratings used without telescopes saw no more. 



Mr. Bennet (Amer. Jour. Sci., vol. xvi, p. 287), with a very eflicient integrating spectroscope saw 

 1474 K and F for a few seconds after the beginning of totality and again for a few seconds before 

 its termination. 



Professor Bakkee (Proc. Amer. Ass. Adv. Sci., 1878, p. 113) used a direct- vision analyzing spec- 

 troscope, with telescope and collimator having 4inch focal lengths and finch apertures. The dis- 

 persive power was nearlj- equivalent to that of two 00° prisms. This instrument was attached to 

 a 4-iuch telescojje by Jones, of London, not otherwise described. If we assume the ordinary ratio 

 of aperture to focal length in the image lens, i. e.. jVi ^^ fi"'l that the effective aperture of the 

 si»ectroscope was only about ^ of an inch. No bright lines, but numerous dark lines were seen 

 Of these, h and F were esitecially distinct,* and D, E, and G considerably less so. They were all 

 faiuter than in an ordiiuiry solar spectrum of the same brightness. 



Professor Eastman (U. S. N. Obs. Eep., 1878, p. 299) employed a siugle prism instrument with 

 an effective aperture of 0.9 of an inch ; power not stated. With a wide slit he traced 1474 K to a 

 distance of from 10' to 14' froui the moon's limb. No other lines were seen. 



Professor Harkness (U. S. N. Obs. Eept., 1878) confined his attention to the ultra-violet region 

 of the spectrum, where he tailed to find any lines. 



Commander Sampson (U. S. N. Obs. Kept , 1878, p. 113) does not give the essential constants 

 of his instrument. Using a narrow^ slit, the observer failed to see either bright or dark lines in the 

 continuous spectrum exhibited. 



Professor Young (Amer. Jour. Sci., vol. xvi, p. 285) employed a single-prism spectroscope with 

 a fluorescent eye-piece. The field of view extended from about C to above F. C, D3, 1474 K and F, 

 were visible throughout totality. Of these, C was traced to a height of 10' and F of 5' from the 

 moon's limb. 



* It will be seen that Professsor Young found F a bright coronal Hue tlironyhont this eclipse. 



