April 25, 1913] 



SCIENCE 



649 



established. The results for any given diaphragm 

 or screen establish a scale for the bright stars 

 which should be homogeneous with the adopted 

 scale for the faint stars, and, as far as the slope 

 is concerned, independent of the reduction con- 

 stant of the diaphragm. With one exception, the 

 results for all the diaphragms and screens used 

 are in substantial agreement, and show a mean 

 divergence between Mt. Wilson and Harvard ex- 

 pressed by 



Mt. W. — H. = + 0"'.33 + 0"'.075(lf— 10.5). 

 The formula holds between magnitudes 2 and 

 10.5. From 10.5 to 15.5 the scales are parallel, 

 with the constant difference + 0".33. The Mt. 

 Wilson results agree closely with those of Park- 

 hurst and Schwarzschild, which extend from mag- 

 nitude 4.0 to 7.5. 

 The Photographic and Visual Light-curves of 



BB Dra<:onis: Frederick H. Seares. 



At the fourteenth meeting of the society an 

 announcement was made concerning the photo- 

 graphic variation of the Algol star BB Draconis. 

 The eclipse is necessarily that of a bright object 

 by a larger and fainter companion. The relative 

 amounts of light are approximately as 32 to 1, 

 and probably the larger object is the redder of 

 the two. The photographic variation should there- 

 fore exceed the visual. This hypothesis was tested 

 by photographing the star upon ordinary and iso- 

 chromatic plates, the latter being used in connec- 

 tion with a yellow filter. The photographic and 

 photovisual magnitudes of the comparison stars 

 were determ in ed by the use of diaphragms, the 

 zero points of both scales being fixed by com- 

 parisons with the Harvard Polar Sequence. The 

 greater photographic range is clearly shown. The 

 results are 



Photo- Photo- Color- 

 graphic visual Index 



Maximum 9.64 9.98 — 0.34 



Minimum 13.46 13.23 + 0.23 



Amplitude 3.82 3.25 0.57 



The epochs of photographic and photovisual 

 minima are probably the same. The maximum 

 difference permitted by the present series of meas- 

 ures is 0.002 day, the photovisual minimum fol- 

 lowing the photographic. 

 Some Becent Changes in the Spectrum of Nova 



Gemimorum No. 2: R. H. Curtiss. 



On December 4, 1912, Nova Geminorum No. 2 

 was found to be passing through a period of 

 marked light recovery. Its brightness, 7.5 magni- 

 tude, was identical with its former value seven 



months previous or about eight weeks after dis- 

 covery. During two weeks following December 8 

 the Nova faded rapidly down to magnitude 8.3. 

 Visually the Nova was of a decided greenish-blue 

 color during this period. The spectrum, however, 

 underwent some marked changes. 



At the brighter phase of the Nova's recovery 

 the hydrogen lines and \ 4635 had developed 

 greatly in strength and intensity, but with de- 

 clining light the nebular lines had become the 

 strongest feature of the spectrum. Our observa- 

 tions indicate that the nebular lines actually 

 gained in brightness or at least held their own 

 while the total light of the star waned, but during 

 the same interval the hydrogen lines faded rapidly. 



Eadial velocities from the dark H line of cal- 

 cium agree with the value of ten kilometers per 

 sec. positive, obtained shortly after the Nova's 

 discovery. 



Bo the Declinations of the Accepted Fundamental 



Catalogues Bepresent the True Positions of the 



Stars? W. S. Eichelbeeger. 



From two papers presented at the Ottawa meet- 

 ing by F. B. Littell, on the work of the 6-inch 

 transit circle, and on the work of the altazimuth 

 at the Naval Observatory it appears that the 

 declinations of the stars in Boss's General Cata- 

 logue culminating south of the Washington zenith 

 require a correction of about -|- 0".5. 



This result is confirmed by the results in the 

 volume of the Greenwich Observations for 1908, 

 and the results obtained with the 9-inch transit 

 circle of the Naval Observatory. Further, the 9- 

 inch results show a practically constant correction 

 from declination — 30° to declination -f 45°, a 

 rapid but nearly uniform decrease in the size of 

 the correction from declination -|- 45° to declina- 

 tion + 60° and a nearly zero correction from that 

 point to the pole. The rapidly changing correc- 

 tion a few degrees north of the zenith with a 

 constant correction through the same zenith-dis- 

 tances south of the zenith would indicate that the 

 fault can hardly be in the instrument. Can it be 

 in the declinations of the fundamental catalogue? 



If there is a discontinuity at the zenith in the 

 determination of declinations at the various Euro- 

 pean observatories due either to the instrument or 

 to the observer, such an error as supposed may have 

 been introduced into the fundamental catalogues. 



The following table, giving the differences be- 

 tween the declinations of three pairs of Pulkowa 

 and Greenwich Catalogues, shows that such a dis- 

 continuity exists at least in some of the catalogues. 



