1 84 ASTRONOMY. 



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

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

 tified and their positions determined. The work done during the last 

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

 vations taken in earlier years, with which the pajjer of 1801 made the 

 scientific world acquainted. Most of the more important nebulte having 

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

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

 metric measures of groups of nebulfe, or of nebula and neighboring stars. 

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

 and the stars near it, while four plates contain lithographic reproduc- 

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

 among the engravings in the former papers. How much more detail is 

 given in the new publication than in the paper of 1801 may be seen from 

 the circumstance that while the fourteen hours of E.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 nebulfe 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 nebulaj found on his ecliptic charts. 



Fliotographs of the Nebula of Orion. — Prof. Hbnby DRAPER, distributed 

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

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

 Stars down to the 10th magnitude were shown and the details of the 

 more prominent masses of the central and brightest regions were for 

 the first time permanently and automatically registered. The work so 

 well begun has been brilliantly prosecuted, and in March, 1881, Dr. 

 Draper succeeded in obtaining fine photographs with an exposure of 

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

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

 they show stars whose magnitudes Prof. Pickering has photometri- 

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

 mum vi.sihile of an 11-inch telescope is about 14.2, so that it really ap- 

 pears that Dr. Draper has photographed stars which are very near 

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

 l)erfection of the apiiliances which render such feats possible can oidy 

 be appreciated by those used to the apparatus furnished by the best 

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

 use. 



FIXED STARS. 



Fixed stars, catalogues of stars, star charts, double stars, binary stars, 

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

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



*"Resultaclos del Observatorio Nacional Argentma." Vol. I, "Uranometria Ar- 

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



