446 



SCIENCE. 



[N. S. Vol. XXIII. No. 586. 



discriminately throughout the sky, but that 

 the younger stars, type I., show a more pro- 

 nounced tendency to cluster along the milky 

 way than do the mature ones, and this tend- 

 ency grows more and more pronounced with 

 diminishing brightness of the stars. It is 

 difficult to see why this should be so; Avhy 

 one part of the universe should lag behind 

 the rest in development, but the new 

 hypothesis indicates at once that such is 

 not the case. The distribution found by 

 Professor Pickering is only an apparent 

 one depending upon the known fact that 

 the type I. stai's are intrinsically brighter 

 than their companions of type II. This 

 fact alone in a system such as is here sup- 

 posed would produce an increasing accumu- 

 lation of faint, and therefore distant, stars 

 of this type in the region adjoining the 

 millry way, although, in fact, the two types 

 may be everywhere distributed with a uni- 

 form ratio of frequency. 



Other matters can be touched upon here 

 in a summary way only. It is ^n im- 

 mediate consequence of the present hypoth- 

 esis that any considerable group of stars in 

 a part of the sky remote from the milky 

 way must on the average be nearer to us 

 than a group of similar stars in the milky 

 way. Although this relation has not been 

 recognized hitherto, the writer finds from 

 his own observations of faint stars between 

 the ninth and twelfth magnitudes that such 

 is the fact, the stars in the milky way be- 

 ing twenty-eight per cent, more distant 

 than the mean of all other stars. It is com- 

 monly stated that the brightest stars emit 

 an amount of light enormously greater 

 than that given by the sun, 1,000 or 10,000 

 times as much, but from the measured 

 magnitudes and distances of the stars it 

 appears that while the large majority are 

 brighter than the sun, few if any are more 

 than two hundred times as bright. 



Much of the investigation contained in 

 this paper is summed up in a series of for- 



mulas, one of which shows the number of 

 stars in the sky that are brighter than a 

 given magnitude, e. g., the tenth. Another 

 shows the average distance of the stars of 

 any assigned magnitude. A partial proof 

 of the substantial accuracy of the numerical 

 work contained in the paper is found in 

 the fact that this last formula, although 

 based solely upon distances of the fainter 

 stars, derived by an indirect process, is in 

 excellent agreement with the directly meas- 

 ured distances of the brightest stars. 



Photometric Investigations: F. H. Seakes. 



This paper is a summary of results in an 

 investigation of the wedges belonging to a 

 Pickering equalizing stellar photometer. 

 Two wedges were examined ; one of photo- 

 graphic film, the other of shade glass. Ab- 

 sorption curves were determined by means 

 of a disc photometer. The magnitude 

 scales underlying these curves were then 

 compared with that of the Miiller and 

 Kempf catalogue of Pleiades stars. Magni- 

 tude differences of twenty-one pairs of stars 

 were measured and the results compared 

 with the catalog-ue. The stars observed 

 range from 7.24 to 10.76 magnitudes; the 

 magnitude differences, from 0.80 to 3.52 

 magnitudes, with an average of 1.8 mag- 

 nitude. 



Eight observations were made with the 

 shade glass wedge upon each pair. With 

 three exceptions, each pair was measured 

 upon at least four different nights. The 

 results for this wedge are : P.E. of a single 

 observation of four comparisons, ± 0.066 

 mag. ; average deviation of mean magni- 

 tude difference from the catalogue differ- 

 ence, 0.07 mag. ; deviation of wedge magni- 

 tude scale from the scale of Miiller and 

 Kempf, for the range 8.2-10.0 magnitudes, 

 + 0.028 mag. The scale agreement is to 

 be considered satisfactory, since the devia- 

 tion is not greater than may arise from 

 personality alone. 



