398 SPECIAL RESULTS IN THE TJRANOLOGICAL 



In comets seen with the unassisted eye, recent times 

 have been more rich than was the latter part of the last 

 century ; but still the appearance of a comet brilliant in both 

 head aud tail continues to be a rare and remarkable natural 

 phsenoinenon. It may not be without interest to reckon up 

 the number of comets which have been seen in Europe with 

 the naked eye during the last few centuries ( 649 ). The 

 richest period was the 16th century, when 23 such comets 

 were seen. The 17th had 12, of which only 2 were in the 

 first half. In the 18th century only 8 such comets 

 appeared, whereas we have had 9 in the first fifty years of 

 the 19th. Of these, the finest were those of 1807, 1811, 

 1819, 1835, and 1843. In earlier times it has happened 

 more than once that from thirty to forty years have passed 

 without the record of such a spectacle having been once en- 

 joyed. The years which appear poor in comets may, however, 

 for aught we know, have been actually rich in large comets 

 having their perihelions situated beyond the orbits of Jupiter 

 and Saturn. Of telescopic comets, there are now discovered, 

 on an average, at least two or three a year. In three suc- 

 cessive months, in 1840, Galle found 3 new comets ; from 

 1764 to 1798 Messier found 12 ; and Pons, from 1801 to 

 1827, found 27. Thus Kepler's expression respecting the 

 multitude of comets in space (" ut pisces in oceano") almost 

 appears to be justified. 



The careful register of the comets seen in China, made 

 known to us by Edouard Biot from the collection of Ma- 

 tuan-lin, is of no small importance. It extends back beyond 

 the foundation of the Ionic school of Thales and the Lydiau 

 Alyattes, and comprises in two sections the places of comets 

 from 613 years before, to 1222 after our era; and from 



