PROGEESS AND PEOBLEMS OF SOLAE PHYSICS 

 DUEING THE LAST FIFTY YEAES. 



BY DAVID E. HADDEN. 



At the beginning of the century which has recently 

 passed into history little was known of the science of 

 Astronomical Physics, absolutely nothing was known 

 about the physical composition of the sun, planets or 

 stars. In the year 1802 Wollaston was enabled to see the 

 dark lines in the solar spectrum by substituting a slit for 

 the round hole of Newton's method for studying the spec- 

 trum, but he, supposing that these dark intervals were 

 simply boundaries between the seven primary colors of 

 the spectrum, gave the matter no further attention and 

 Astrophysics had to wait for fifty years, until Swabe an- 

 nounced the discovery of the Sunspot period in 1851, 

 when it was soon found that the earth's magnetism and 

 the displays of Northern Lights obeyed the same law 

 of change. 



A few years later Kirchoff in his studies of the solar 

 spectrum announced to the Academy of Sciences of Ber- 

 lin the results of his investigations into the chemical 

 interpretation of the lines in the solar spectrum and the 

 presence in the sun of iron, calcium and other familiar 

 metals, this classic discovery was the beginning of the 

 modern science of Astrophysics, 



Astro chemistry now developed with rapidity and 

 the spectroscope became a new and powerful instrument 

 of research; the brilliant beams of sunlight, as well as 

 the feeble rays from myriads of stars, were awaiting the 

 results of analysis by means of the integrating prism. 



In 1864 Dr. Huggins (now Sir Wm. Huggins) began 

 his studies of the spectrum of nebulae and showed that 

 planetary and all irregular shaped nebulae were largely 

 of a gaseous constitution, and in 1876 he introduced 

 photography to the study of stellar spectra, and since 



