184 THE SUN— ITS CHEMICAL ANALYSIS. 



to doubt that the sun has an atmosphere of a temperature lower than 

 that of the luminous nucleus, properly so called, and which holds in 

 suspension the greater part of the simple bodies which we find on our 

 planet. This grand conception accords well with the hypothesis of 

 Laplace, who attributed the formation of all our planetary system to 

 the gradual cooling of a single nebula, in which the cosmic matter at 

 present condensed in the sun, the planets and the satellites, was 

 primitively diffused through th% entire space which that system oc- 

 cupies. The smallest bodies naturally cool most rapidly; the moon 

 appears frozen, without atmosphere, without water, without organic 

 life; there is something mournful and appalling in its aspect under 

 the telescope. The earth has cooled less promptly than its satellite, 

 but far more rapidly than the sun, whose fervid atmosphere still con- 

 tains the numerous substances which on our planet have been long 

 since condensed and fixed in the solid rocks. Our impoverished at- 

 mosphere contains nothing but the elements necessar}^ for the support 

 of organic life, oxygen, azote, carbon, and water, and our understand- 

 ing can with difficulty accustom itself to the idea of an atmosphere 

 charged with iron, with alkaline metals, with bodies the most differ- 

 ent in a state of combustion. It would require the pen of Dante to 

 portray that chaotic condition of nature, that rain of metallic fire, 

 those luminous clouds darkened by the contrast of a still intenser 

 light, that incandescent ocean of the sun, with its tempests, its cur- 

 rents, its rushing and gigantic water-spouts; such pictures set at de- 

 fiance even imaginations the most enamored of the fantastic and the 

 strange, and our dreams evaporate as a drop of water before that 

 blazing lava, that focus, that refulgence of the world, source of all 

 warmth, of all movement, of all life. 



On such a subject nothing can be more eloquent than the precise 

 language of science; it derives its force from its very humility. If 

 metallic vapors surround the sun in the form of an atmosphere, we 

 comprehend that they may be condensed in clouds, like the vapor of 

 water in our own atmosphere. Galileo regarded the spots of the sun 

 as clouds floating before the lustrous body from which the light radi- 

 ates; but this h3^pothesi8 has been generally abandoned by astrono- 

 mers. In order to understand the theories which are at present 

 adopted respecting the physical constitution of the sun, let us describe 

 the appearance which it presents when examined under a high 

 magnifying power. 



The entire surface appears covered Avith innumerable small in- 

 equalities, similar to marbling, or rather to the rugosities of an 

 orange. On the luminous ground are seen dark spots of a brownish 

 grey or black color, and of very irregular forms. When these 

 spots are observed for several days in succession we perceive that 

 they make their appearance on the eastern border of the disc, ad- 

 vance towards the centre, pass it, and disappear behind the western 

 border. Sometimes the same spots are seen to reappear after having 

 made an entire circuit. It is this phenomenon, indeed, which has 

 afforded the means of estimating the velocity of rotation of the sun. ' 

 The spots of the sun have very distinct outlines; they usually exhibit 



