May 25, 1888.] 



SCIENTIFIC NEWTS. 



48s 



NEW PHOTOGRAPHIC MAP OF THE 

 PLEIADES. 



SOME time ago the brothers Henry discovered, by 

 means of photography, a nebulosity surrounding 

 the star Maia in the Pleiades ; this nebula was very 

 faint, and was quite invisible in the best telescopes of 

 the Paris Observatory. Shortly afterwards it was seen 

 with the large refractor, of thirty inches aperture, at the 

 Pulkowa Observatory, and when the new telescope of 

 about the same size was erected at Nice, the nebula was 



negatives taken on the i6th November and 14th 

 December, 1887, the exposure in each case being four 

 hours. 



This map shows that considerable advance has been 

 made in the two years. This progress may be attributed 

 to the greater sensitiveness of the plates, and to the more 

 thorough knowledge of the apparatus and photographic 

 processes. 



The feeble traces of nebulosity which in 1885 appeared 

 round Maia,M6rope and Electra are now shown as well de- 

 fined nebulse, of complex structure, nearly joined to each 



Chart of a Portion of the Pleiades Groups. 

 The magnitude of the stars is shown by the size of the circles. 



seen by M. Perrotin with sufficient clearness to enable 

 him to sketch it. 



Since its discovery the photographic process has been 

 greatly improved by MM. Henry, who intend to take 

 negatives of this group of stars every year, with the 

 double view of ascertaining whether any changes have 

 occurred, and what progress they have made in photo- 

 graphing very faint stars. 



In constructing the map, the most interesting portion 

 of which we give in our illustration borrowed from La 

 Nature, the print taken in 1886 was used, and to it was 

 added the new nebulosities and stars appearing on two 



other : another spreading nebula surrounds Alcyone. 

 None of these details have been seen with the most 

 powerful telescopes. 



The most remarkable peculiarity shown in these 

 photographs are two long and very thin filaments 

 of cosmic matter, nearly rectilinear, and apparently 

 affected by the stars they pass. Nothing of the kind 

 exists in other parts of the sky, so far as we know at 

 present, and unfortunatel}' they are so faint that it will 

 be scarcely possible to see and observe them directly. 



One of these objects is situated about 23° 41' N. 

 Declination, and extends from 3h. 37m. 50s. Right 



