REPORT OF THE SECRETARY. 



29 



It is noteworthy that last year is the first ouc since 1859 in wliich 

 more thau one planetoid has not been discovered. The animal numbers 

 recorded during the last twenty-five years are as follows : 



1857 9 



1858 5 



18i)9 1 



1860 5 



1861 10 



30 



1877 11 



1878 12 



1879 20 



1880 8 



1881 1 



52 



It thus appears that the quinquennial average of discoveries, so far 

 from decreasing, has for the past twenty years steadily and notably in- 

 creased, giving BO indication, therefore, of an iuimediate or early ex- 

 haustion of material. This is due, partly, to the closer scrutiny given 

 to this field by astronomers, partly to the increased number of ob- 

 servers, and partly to improvements in their instruments and in their 

 systematic methods of observation. 



This remarkable group of planetoidal or meteoroidal bodies forms a 

 tolerably wide zone or ring between the orbits of Mars and Jupiter, 

 separating the four interior and smaller planets (including our earth) 

 from the four exterior and much larger planets. It has been estimated 

 by Leverrier and others, from the motion of Mars (the amount of dis- 

 placement of the apsides, due to the amount of counteraction of the 

 solar gravitation by the external attraction), that the entire mass of 

 this ring of meteors cannot much exceed a fourth of that of our earth. 

 In no great time, therefore, the discovery of new members of this group 

 must become more and more rare. The smallest thus far observed do 

 not probably exceed 20 or 30 miles in diameter, and the number which 

 will remain forever unseen, by even the highest powers of the telescope, 

 may very many times surpass the number ever made visible. 



List of comets observed in 1881. 



No. 



I 



II 

 III 

 IV 



V 



VI 



VII 



VIII 



Name. 



Faye's comet. 



Encke's comet . . . 



Discoverer. 



Swift 



Tebbiitt 



ScbcBberlo 



Commou 



E. E. Bernard 



Deiiniug 



Swift 



Observatory. 



Rochester, N. Y. 

 Windsor, New South Wales. 

 Ann Arbor, Miih. 

 Ealing, England. 

 Nashville, Tonn. 

 Bristol, England. 

 Rochester, N. Y. 



The generous co-operation of the large telegraph companies, embrac- 

 ing those both of the transatlantic cable and of the widely ramified 

 land lines, cannot be too often or too warmly acknowledged. The lib- 



