August 1, 1895.] 



KNOWLEDGE 



181 



to "very feeble," II. to "feeble," V. to "luminous, 

 to " very luminous," etc. 



On comparing the stellar densities for the 

 stars 9-1 to 9-5, with my map of the Milky 

 Way in this part of the heavens, it is found 

 that the feeblest densities correspond to the 

 places where the Milky Way presents the least 

 brilliancy, and that the density is the great- 

 est there where the intensity of the Galactic 

 glimmer is the strongest. As in default of a 

 good photometric method, the values I., IV., 

 etc., for the intensity of the Galactic bright- 

 ness cannot always represent one and the same 

 intensity, a comparison of the contrasts oflfered 

 by neighbouring regions should above all be 

 made. Table 11., representing the differences in 

 densities, has been added for this reason. 



Table II. 



VI. 1 William Herschel (Pub. Washbuni II.), and the unpub- 

 j lished gauges that Dr. Th. Epstein of Frankfort-on-Main 



Fi 



a 4.- 

 the 



•Duigram intliea'ing the stellar density for Stars of magnitude 1 — 11. 

 ■ (Celoria.) 



has been good enough to communicate to me ; and to 

 complete these data by countings carried out for the same 

 regions on the Bonn atlas, and on Max Wolfs two 

 photographs, reproduced in Knowledge, December, 1891. 

 The limits of the magnitudes are naturally only given 

 approximately. On combining these results for the places 

 where the Milky Way presents either a feeble intensity, a 

 strong intensity, or an average intensity, the following table 

 is obtained for the averages of the number of stars found 

 on a superficies of 1100 square minutes (the superficies 

 of the Epstein gauges), for the columns II to V., compared 

 with the averages of the Herschel gauges. 



Table III. 



Excepting the zone where the "coal sack" (M-0) is 

 found, and where the correspondence shows clearly from 

 the seventh magnitude, it is seen that the group 9-1 to 

 9'5 is the only one for which the signs correspond nearly 

 everywhere with those of the col. II. 



With the exception of a single instance (D-E) — of 

 small importance, and which may be attributed to an 



Fig. 3. — Diagram indicatiug th; 



stellar density for Stars of magnitude 9 1 

 (Argelauder.) 



erroneous estimate of the average brilhancy of the Milky 

 Way in this region — it appears from the preceding tables 

 as well as from the table representing the results obtained 

 from the zone in the Eagle, that the stars of the last 

 class of Argelander already present, by the manner in 

 which they are distributed, a remarkable correspondence 

 with the luminous and obscure spots of the Milky Way. 



For this region it has been possible to compare one with 

 the other a rather large number of stellar gauges by 



We have found that the maxima and the minima of the 

 stars of the 9th, 12th, 15th magnitudes fall in the same 

 places of the heavens, often with astonishing precision, 

 and this in rather extended zones and which embrace 

 nearly the whole of the breadth of the Milky Way. 

 This does not mean that such will be the 

 case for all regions of the heavens ; such 

 a supposition, indeed, is very improbable. But 

 that such a coincidence, occurring so often, 

 can be a mere chance is hardly admissible ; 

 thus it cannot be here a matter of groups in- 

 dependent one of the other. Besides, in all 

 cases where these condensations have an 

 appreciable Galactic latitude, it would have to 

 be admitted that the real latitudes of the groups 

 situate at divers distances in the direction of 

 our visual ray were, for each one of them, 

 nearly exactly proportionate to the distances, 

 which would seem absurd. 

 It is true that a hypothetical stellar ring, from which 

 extend protuberances in the direction of our visual rays, 

 would give rise to an analogous phenomenon to that 

 which we have just stated. But in order to explain all 

 the facts, particularly the circumstances that the correlation 

 which has been found is just as often met with in the 

 very feeble regions as in the luminous regions, it must 

 be admitted that the length of these protuberances must 

 be relatively slight. This circumstance, and the com- 



-9-; 



