122 Sioux City Academy of Science and Letters. 



that time the progress of this branch of Astronomy has 

 been rapid and marvelous; in fact, the wonderful prog- 

 ress which Astronomy and Astrophysics have made dur- 

 ing recent years is largely due to the adoption of Astro- 

 photography. 



Astrophysics, though widening in scope each year, 

 is but yet in its infancy, the problems confronting the 

 astronomer of today in seeking to solve the physical con- 

 stitution of sun, moon, planets, asteroids, comets and 

 distant stars and nebulae are well nigh as boundless as 

 the universe in which they shine, and with every advance 

 in our knowledge of them proving to man in the w^ords 

 of Addison that "The hand that made them is divine." 



The progress of solar physics during the past fifty 

 years has been marked by many far reaching and bril- 

 liant discoveries; it was during the total eclipse of the 

 sun July 18, 1860, that the photogTaphic plate demon- 

 strated the solar location of the red prominences and at 

 the Indian eclipse of August 18, 1868, the spectrum of 

 the prominences was observed to consist of the bright 

 lines due to hydrogen and helium. In the following year 

 the Coronium ray was seen, and in 1870 Professor C. A. 

 Young caught sight of the momentary but brilliant flash 

 spectrum of the reversing layer, which in recent years 

 has been so successfully photographed. 



It was early discovered after the interpretation of 

 the Praunhofer lines that the old Herschelian theory of 

 the sun was doomed, and it remained for the New As- 

 tronomy to formulate solar theories, which are yet in 

 process of elucidation and verification. 



Our sun is not a solid, nor yet a liquid globe: it is 

 mainly of the critical gaseous liquid nature subjected to 

 tremendous pressure and temperature, with enormous 

 convection currents carrying their supply of electrical 

 or other energy in an increasing quantity from the reser- 

 voirs beneath to the photosphere above; over this dazzl- 

 ing surface the spectroscope has demonstrated the exist- 

 ence of several shells or envelopes and has enabled us 

 to determine their constitution. 



Professor Young ^^^ regards the photosphere as a 

 shell of clouds, columnar in form owing to the ascending 



