GROWTH IN OUR KNOWLEDGE OF THE SUN 



By Charles E. St. John 



[With 7 plates] 



The ilifToroiu'es botwoon tho two r('i)resentatioTis of tho sun (pi. 1) 

 show graphically the wide conti-ast between the appearance of the 

 sun as observed and imagined in 1C35, and as photographed nearly 

 300 years later as a composite of spectroheliograms of disk and 

 ciiromosphere. 



The gulf between the past and the present knowledge of the sun 

 has been bridged in comparatively recent years, almost within the 

 lifetime of men now living. 



Though absorption lines in the solar spectrum were first observed 

 by Wollaston in 1802 and catalogued to the number of 576 by Fraun- 

 hofer in 1814. the real beginning of astrophysics dates from Kirch- 

 off's great discovery, in 1859, of the true interpretation of the Fraun- 

 hofer lines. The application of spectroscopic analysis to astronomi- 

 cal problems opened broad vistas to active and progressive spirits. 

 Huggins says, "The news of Kirchoff's discovery was to me like 

 coming upon a spring of water in a dry and thirst}' land." The first 

 triumplis of the spectroscope were won by its application to the sun. 

 It is interesting to note, however, that in the hands of Huggins and 

 Draper the novel method of research was e.xtended to stars, nebulae, 

 and comets with great success before further uses were found for it 

 in solar work. 



I.ockyer and Janssen in 18G8 made a great advance through their 

 indej)endent observations that the blood-red chi'omosphere and 

 prominences, hitherto seen only during a total eclipse of the sun, are 

 gaseous and owe their redness to the emission of the red line of 

 liydrogen; and by the discovery of helium in the sun a quarter of a 

 century before it was traced to an earthly source. A romantic touch 

 was thus given to the study of the sun. 



' ReiiriiiH<l by poi iiilssloii, witli uuLImji's alhiiitioiiM aJid additions, from riiblitaUoiiH 

 of the Astronomical Society of tlie I'uclflc, vol. 41, No. 241, Jun<s li)*J'J. 



177 



