CH. viii., $$ 152-154] Telescapic Discoveries 199 



To his rival Christopher Scheiner (chapter vi., 124, 125) 

 belongs the credit of the discovery of bright cloud-like 

 objects on the sun, chiefly visible near its edge, and from 

 their brilliancy named faculae (little torches). Scheiner made 

 also a very extensive series of observations of the motions 

 and appearances of spots. 



The study of the surface of the moon was carried on 

 with great care by John Hevel of Danzig (1611-1687), who 

 published in 1647 ms Selenographia, or description of the 

 moon, magnificently illustrated by plates engraved as well 

 as drawn by himself. The chief features of the moon 

 mountains, craters, and the dark spaces then believed to be 

 seas were systematically described and named, for the 

 most part after corresponding features of our own earth. 

 Revel's names for the chief mountain ranges, e.g. the 

 Apennines and the Alps, and for the seas, e.g. Mare 

 Serenitatis or Pacific Ocean, have lasted till to-day ; but 

 similar names given by him to single mountains and craters 

 have disappeared, and they are now called after various 

 distinguished men of science and philosophers, e.g. Plato 

 and Coppernicus, in accordance with a system introduced 

 by John Baptist Ricdoli (1598-1671) in his bulky treatise 

 on astronomy called the New Almagest (165 1). 



Hevel, who was an indefatigable worker, published two 

 large books on comets, Prodromus Cometicus (1654) and 

 C0metogra#Aia(i66&), containing the first systematic account 

 of all recorded comets. He constructed also a catalogue 

 cf about 1,500 stars, observed on the whole with accuracy 

 rather greater than Tycho's, though still without the use of 

 the telescope; he published in addition an improved set 

 of tables of the sun, and a variety of other calculations and 

 observations. 



154. The planets were also watched with interest by a 

 number of observers, who detected at different times bright 

 or dark markings on Jupiter, Mars, and Venus. The two 

 appendages of Saturn which Galilei had discovered in 1610 

 and had been unable to see two years later (chapter vi., 123) 

 were seen and described by a number of astronomers 

 under a perplexing variety of appearances, and the mystery 

 was only unravelled, nearly half a century After Galilei's first 

 observation, by the greatest astronomer of this period, 



