158 ON THE ORIGIN OF THE PLANETARY SYSTEM. 



rounded by a photosphere which only radiates heat 

 and light externally, contains a physical impossibility. 



Outside the opaque photosphere, the sun appears 

 surrounded by a layer of transparent gases, which are 

 hot enough to show in the spectrum bright coloured 

 lines, and are hence called the Chromosphere. They 

 show the bright lines of hydrogen, of sodium, of magne- 

 sium, and iron. In these layers of gas and of vapour 

 about the sun enormous storms occur, which are as 

 much greater than those of our earth in extent and in 

 velocity as the sun is greater than the earth. Currents 

 of ignited hydrogen burst out several thousands of miles 

 high, like gigantic jets or tongues of flame, with clouds 

 of smoke above them. 1 These structures could for- 

 merly only be viewed at the time of a total eclipse of 

 the sun, forming what were called the rose-red pro- 

 tuberances. We now possess a method, devised by 

 MM. Jansen and Lockyer, by which they may at any 

 time be seen by the aid of the spectroscope. 



On the other hand, there are individual darker 

 parts on the sun's surface, what are called sun-spots, 

 which were seen as long ago as by Galileo. They are 

 funnel-shaped, the sides of the funnel are not so dark 

 as the deepest part, the core. Fig. 10 represents such 



1 According to H. C. Vogel's observations in Bothkamp to a height 

 of 70,000 miles. The spectroscopic displacement of the lines showed 

 velocities of 18 to 23 miles in a second; and, according to Lockyer, of 

 even 37 to 42 miles. 



