The Sun 



Among those to whom we owe our knowledge 

 of the sun's disc a leading place is due to Father 

 Secchi, director of the observatory of the Collegio 

 Romano, whose observations, untiringly con- 

 centrated on this single object, have been con- 

 densed into an admirable book. 1 



We may add that during the last thirty years 

 photography has been of great use to observers; 

 by enabling them to fix the most transient 

 details of phenomena it has provided a means 

 for studying them at leisure and drawing from 

 them fruitful comparisons. 



Let us consider now the facts which the study 

 of the sun's surface has revealed. We find first 

 of all that this surface, far from being uniform, 

 appears on the contrary irregular and undulating, 

 and, under strong magnification, seems covered 

 with a multitude of little bright grains, like 

 grains of rice, separated by a dark network; in 

 some places more extensive bright masses appear, 

 called faculae; the grains may be two to three 

 kilometres long, the faculae perhaps ten times 

 longer. It is, however, the sun-spots which 

 form the most striking feature of the solar 



1 Le Soldi. Gauthier-Villars, Paris, 1875. 

 161 



