184 ASTRONOMY. 



formed the weak point of Herschel's General Catalogue, have now by 

 re-examination and comparison with D'Arrest's observations been iden- 

 tified and their i)ositions determined. The work done during the last 

 five or six years (1872-'78) differs in many particulars from the obser- 

 vations taken in earlier years, with which the paper of 18G1 made the 

 scientific world acquainted. Most of the more important nebulfe having 

 been fiequently drawn, there was latterly not much to be done in this 

 direction, but another important field was opened up by taking micro- 

 metric measures of groups of nebulae, or of nebulse and neighboring stars. 

 Into tbe text have been introduced diagrams of such groups or of a nebula 

 and the stars near it, while four i)lates contain lithographic reproduc- 

 tions of more elaborate sketches, which had not already been published 

 among the engravings in the former i)apers. How much more detail is 

 given in the new publication than in the pa|)er of 18(>1 may be seen from 

 the circumstance that while the fourteen hours of li.A. in the latter only 

 cover 34 pages, in the new paper they extend over 129 pages. 



A series of measurements of all the planetary nebulre has been com- 

 menced with the l'»-inch refractor of the Harvard College Observatory. 



Dr. C. H. F. Peters has lately published in Urania an important 

 list of nebulae found on his ecliptic charts. 



Fkofographs of the Nchula of Ono«.— Prof. Henry Draper distributed 

 in 1880 a large number of photographs of the nebula in Orion, taken by 

 means of his 11-inch Clark refractor with an exposure of 51 minutes. 

 Stars down to the lOtli magnitude were shown and the details of the 

 more prominent masses of the central and brightest regions were for 

 tbe first'time permanently and automatically registered. The work so 

 well begun has been brilliantly i)ro8ecuted, and in March, 1881, Dr. 

 Draper, succeeded in obtaining fine jdiotographs with an exposure of 

 140 minutes! These give a much greater extent to the nebulous por- 

 ticras registered and bring out many details, and what is astonishing 

 they show stars whose magnitudes Prof. Pickering has pliotometri- 

 cally determined to be from 14.0 to 14.7 of Pogson's scale. The ^nini- 

 viuni vikihile of an 11-inch telescope is about 14.2, so that it really ap- 

 pears that Dr. Draper has ])hotographed stars which are very near 

 the limit of naked eye vision if not actually below it. The mechanical 

 perfection of the appliances which render such feats possible can only 

 be ax)preciated by those used to Ihe apparatus furnished by the best 

 makers, which is far inferior to that made by Dr. Draper for his own 

 use. 



FIXED STARS. 



Fixed stars, catalognes of stars, star charts, (Jovhle ^tars, binary stars, 

 variable stars, etc. — Decidedly the most imijortant recent contribution of 

 observmg astronomy is the "Uranometria Argentina*" of Dr. Gould. 



■ " Resultados del Observatorio Nacioual Argentina." Vol. I, "Uranometria Ar- 

 geutiua," Buenos Aires, 1879, 4to, with, atlas. 



