Spots on the Sun. 281 



sun. About the time that they were first dis- 

 covered by Galileo, forty or fifty of them might 

 be frequently seen on the sun at a time, but at 

 present we can seldom observe more than thirty ; 

 and there have been periods of seven or eight 

 years in which none could be seen. 



The speculations and opinions of philosophers 

 concerning the nature and origin of the solar 

 spots are various, and perhaps all erroneous, 

 since we are in truth unacquainted with the 

 materials of which his body is composed. One 

 of the most popular conjectures is, that they 

 are occasioned by the smoke and opaque matter 

 thrown out by volcanos, or burning mountains, 

 of immense magnitude; and that when the 

 eruption is nearly ended, and the smoke dis- 

 sipated, the fierce flames are exposed, and ap- 

 pear like faculae or little torches. M. de la 

 Hire imagined the sun to be in a continual state 

 of fusion, and that the spots which we observe 

 are only the eminences of large masses of opaque 

 matter, which by the irregular agitations of the 

 fluid sometimes swim upon the surface, and at 

 other times sink and disappear. Nearly akin to 

 this is the more recent hypothesis of Herschel, 

 who supposes the sun to be itself opaque, but 

 surrounded by a phosphoric or luminous atmo- 

 sphere, beyond which the tops of mountains on 

 the sun's body sometimes project, and appear 

 to the telescopic observer as black spots. 



Whatever may be the nature of these spots. 



