cxlii 



NOTES. 



39?. On comets, see Kosmos, Bd. i. S. 105120, and 389393, 

 Anm. 12 27 ; Engl. ed. p. 91 105, and p. xvii, xx. Notes 4257. 



( W9 ) p. 398. In seven half-centuries, from 1500 to 1850, there have 

 appeared in all 52 comets visible to the naked eye in Europe, or taking each in- 

 terval of half a century separately and successively, respectively 13, 10, 2, 10, 

 4, 4, and 9. Taking them thus in half-centuries, and giving the year of the 

 appearance of each comet, we have : 



15001550 

 13 comets. 



15501600 

 10 comets. 



17001750 

 1702 

 1744 

 1748 (2) 



4 comets. 



16001650 

 1607 

 1618 



2 comets. 



1750-1800 

 1759 

 1766 

 1769 

 1781 



4 comets. 



16501700 18001850 



1652 1807 



1664 1811 



1665 1819 

 1668 1823 

 1672 1830 

 1680 1835 

 1682 1843 

 1686 1845 

 1689 1847 

 1696 



9 Comets. 

 10 comets. 



Of the 23 comets stated above to have been visible to t hi naked eye in 

 Europe in the 16th century (the age of Apianus, Girolamo Fracastoro, the 

 Landgrave William the IVth of Hesse, Mastlin, and Tycho Brahe), ten have 



