1 62 HERSCHEL AND HIS WORK 



own and his father's keenness in viewing it till the 

 heat affected their eyes, of his extreme impatience till 

 morning again revealed to him in the sun itself what 

 he thought was only a cloud, and of the incredible 

 delight with which he welcomed the strange stain on 

 the sun's brightness, but removed a little from the 

 place where it was seen the day before he tells a true 

 story with the pen of a romancer inventing a world of 

 wonders. The darkened room, the hole in the shutter, 

 the sheet of white paper to receive the bright image, 

 and the sun's rotation on his axis then burst upon the 

 world in his pages. 



Some imagined that these vast fields of darkness 

 were smoke from gigantic volcanoes on the sun ; 

 others considered them to be a mighty expanse of 

 scum floating on a burning ocean, or dark clouds 

 swimming in highly heated gas. But Herschel's tele- 

 scope told him they were immense pits dug somehow 

 in the shining and fiery brightness, while waves of 

 fiercer brightness surged round the edges in crests of 

 vast height, for which the name faculce, or torches, had 

 been long before invented. Over many million of 

 square miles of the sun's surface this rising of 

 fiercely heated waves and this digging out of black 

 hollows were continually going on in a greater or 

 lesser degree. As many as forty of the latter were 

 once seen by Herschel, when he was watching 

 Mercury, so to speak, picking his way amongst 

 them during his passage across the sun's disc. 

 Other observers laid claim to counting no fewer than 

 fifty at one and the same time. What were they ? 

 In July 1643 Hevelius saw a procession of spots and 

 bright crests more than a third of the sun's surface in 



