ASTRONOMY. 199 



already about 64:,000 zone stars have been observed and mapi^ed. 

 Quite as many more of the fainter stars are needed to comj)lete the 

 maps, and perhaps half of these are now mapped. We possess several 

 series of ecliptic charts, more or less complete. These are : 



1st. Charts by Hind, on which the smallest star is about 11 mag. 



2d. Charts by Chacornac, minimum visibile, 13 mag. 



3d. Charts published by the Paris Observ^atory, in continuation of 

 Chacornac's, minimum visibile, 13 mag. 



The smallest stars laid down on Dr. Peters' charts are 14.8 mag. 



The charts of Chacornac and those of the Paris Observatory are 

 extremely useful, but by no means so complete as those of Dr. Peters; 

 and, in general, they do not cover the same place in the heavens. No. 

 31 of the Paris charts, however, occupies the same ground as one of 

 Dr. Peters' charts. On May 17, 1878, I comjiared the Paris chart 

 No. 31 with the sky, and at the same time I compared Dr. Peters' 

 chart of the same region; and on the following day the two maps 

 were compared together. 



The Paris chart No. 31 contains 1,554 stars, and extends from 10'' 0°^ 

 to 10'' 21'" E. A., and from +8° 45' to + 14° 0' d; the Hamilton Col- 

 lege chart, covering nearly the same ground, extends from lO'' 0"' to 

 10" 20"' E. A., and from + 10° to 15° in <J, The number of stars laid 

 down on the space common to both (from lO'' 0™ to lO'' 16™, and from 

 + 10° to +I40) is, according to the Paris chart, 1,010 stars; according 

 to Dr. Peters' chart, 1,511 stars ; or almost exactly one-half more in the 

 latter. 



I found more than thirty cases where the stars of the Paris chart 

 were either much too large or too small, or where thej^ occupied places 

 where no stars now are. In all these cases the Hamilton College chart 

 was correct. 



Errors in position I naturally could not verify in the time at my dis- 

 posal, but by considering the allineations of the stars as seen in the sky 

 and by comparing these with the data of the Paris chart, I found the 

 latter frequently iucorrect, not always by small amounts. 



The configurations of the group of smaller stars are quite wrong in 

 very many cases, even where all the stars are given; and very many 

 stars are missing of a magnitude superior to the smallest included on the 

 chart. 



In particular, the following stars laid down on the Paris chart do not 

 exist in the heavens : 

 E. A. lOi* 



10 



Large double; only one of 

 which exists. 



