May 13, 1898.] 



SCIENCE. 



661 



ic study of the red stars has been 

 rendered possible by the 40-inch Yerkes 

 telescope. Photographs of the spectra of 

 many objects of this class have now been 

 obtained, and many lines which were not 

 previously recognized on account of the 

 faintness of the spectrum in small telescopes 

 have been recorded. In the case of two 

 stars of Class Illb, 132 and 152 Schjellerup, 

 the spectra have been photographed with 

 a powerful spectrograph containing three 

 prisms, giving high dispersion and consid- 

 erable precision to the measures. It has 

 been found that among the most character- 

 istic features of these spectra are numerous 

 bright lines, some of which seem to have 

 been glimpsed by Secchi in his pioneer work 

 at the Collegio Eomano, though his draw- 

 ings do not correctly represent their appear- 

 ance or position. In fact, he recorded bright 

 lines where none exist, and failed to record 

 others, among which are the brightest in 

 the spectra. Both Duner and Vogel, who 

 are certainly to be regarded as the best 

 authorities on the subject, altogether deny 

 the presence of bright lines. And had my 

 own observations been confined to an exam- 

 ination of the spectra with the instruments 

 used by these observers I would unhesita- 

 tingly subscribe to their opinion. But the 

 great light-collecting power of the 40-inch 

 telescope renders the detection of the bright 

 lines a comparatively easy matter. Even 

 with this instrument, visual observations 

 with the low dispersion spectroscopes used 

 by Duner and Vogel would hardly show 

 them, but they are easily seen with a three- 

 prism spectroscope, and they have been re- 

 peatedly photographed with one and with 

 three prisms. Some of these photographs 

 have been measured and the wave-lengths 

 of the bright and dark lines determined. A 

 comparison of the results with those ob- 

 tained for other types of stellar spectra 

 suggests certain interesting relationships, 

 which, if confirmed by subsequent work, 



will be of service in tracing the course of 

 stellar evolution. 



This is only a single instance of the ad- 

 vantages for stellar spectroscopic work of 

 the great light-collecting power of large 

 telescopes, but it would be easy to multiply 

 examples. Our knowledge of the peculiar 

 spectra of the stars of the "Wolf-Kayet class, 

 all of which are found in the Milky Way or 

 its branches, is due in large part to the 

 visual and photographic study of these faint 

 objects made by Professor Campbell with 

 the Lick telescope. In the able hands of 

 Professor Keeler, whose recent election to 

 the directorship of the Lick Observatory is 

 so truly a cause for congratulation, the same 

 powerful instrument rendered possible the 

 determination of the motion in the line of 

 sight of the planetary nebulae. We may 

 well be confident that the future record of 

 the great telescope on Mt. Hamilton will be 

 marked by many similar advances. 



I might profitably go on to speak of the 

 advantages of large telescopes for the study 

 of the Sun, for in no field of research can 

 they be better employed. In photograph- 

 ing the solar faculse with the spectrohelio- 

 graph the large image given by a great tele- 

 scope is particularly useful for purposes of 

 measurement, as well as for the study of 

 the form and distribution of these phe- 

 nomena. Prominences, too, whether of the 

 quiescent or eruptive class, are best photo- 

 graphed on a large scale. With a large 

 image it may also become possible, under 

 good atmospheric conditions, to photograph 

 some of the delicate details in the chromo- 

 sphere, which, with a small solar image, 

 would be wholly beyond the reach of the 

 photographic method. It is probably in 

 the study of the spectrum of the chromo- 

 sphere, however, that one best perceives 

 the advantage of a large instrument as 

 compared with a small one. Recent ex- 

 perience has made this very clearly evi- 

 dent, for with the 40-inch Yerkes telescope 



