SUNSPO'IS AND SOME OF THEIR TECULIARITIES. 59 



early in the seventeenth century. In 1609, Galileo made his 

 first telescope, and late in 1610, or early in 1611, with one of his 

 improved instruments, he discovered some dark objects on the 

 body of the sun. A little later, a Jesuit Father, Christopher 

 Scheiner, professor of mathematics at Ingolstadt, commenced a 

 regular series of observations of these dark spots, which he termed 

 " Maculae," and he also noted that some parts of the sun 

 appeared to be brighter than the rest of the surface, and he, 

 therefore, called them " Faculae," a name which is still univers- 

 ally given to them. Though Scheiner was able to show these 

 spots to his pupils, he was at first forbidden to publish his 

 observations, except anonymously, as his superiors were sus- 

 picious of his discovery. Thus, when he announced his discovery 

 to the Provincial of his Order, the latter replied : "I have read 

 Aristotle's writings from end to end many times, and I can assure 

 you that nowhere have I found anything similar to what you 

 describe. Go, my son, and tranquillize yourself ; be assured 

 that what you take for spots on the sun are the faults of your 

 glasses or of your eyes.'' 



Sunspots, in appearance are, as their name suggests, dark 

 stains on the intensely brilliant surface of the sun. And a, sun- 

 spot, when fully developed, shows two (or more) grades of dark- 

 ness ; an outer shaded ring known as the penumhra, and an 

 inner, much darker, core which we call the umbra. The penumbra 

 is generally striated ; the umbra in very large spots shows points 

 within itself darker still, w^hich are usually called nuclei. It is 

 characteristic of sunspots that they are associated together in 

 groups, and these groups tend to conform to a certain type of 

 development. At the first appearance, a pair of very small spots 

 are seen near each other. The two members of the pair appear 

 to be repelled, and they move apart ; the two spots increasing in 

 size, and other smaller spots forming between them. The group, 

 therefore, tends to become a stream more or less parallel to the 

 sun's equator. The leader spot is generally very well defined 

 in outline, with its umbra dark and distinct ; the rear spot is 

 usually not so regular in form, or so dark as the leader, though 

 it often is, for a time, the larger of the two. In the early days 

 of the development of a stream, the leader moves rapidly forward 

 from the rear spot, at the speed of about five miles a minute^ 

 that is to say, five or six times the speed of an express train. 

 The photosphere, or bright surface of the sun, appears to be 

 heaped up in front of the leader, and to overflow the small spots- 



