THK NUMUEi; OF THE STARS. 



109 



near Godalming. During the years 1905 to 1909, the northern 

 sky was pliotograplied, the exposure heing increased to 2 hours 

 and 20 minutes for each plate, and experiments were made 

 towards the enumeration and classification of the stars and to 

 ascertain the best means of reproducing the charts on paper. 

 In the course of tliis work, it was found that the northern 

 plates were so superior to those taken at the Cape, that 

 Mr. Franklin-Adams decided to repeat the southern series. 

 Illness prevented him from undertaking this work himself, and 

 in 1909, he presented his 10-inch ol)ject glass to the Transvaal 

 (now the Union) Observatory, and arranged for his assistant, 

 Mr. Mitchell, to go to Johannesburg in Decem])er of that year. 

 The new series of plates was begun in April, 1910. Mr. Mitchell 

 was unable to complete the whole of the southern ])lates, and 

 after his return to England, the series was continued by 

 Mr. Wood under the direction of Dr. Innes, the Director of tlie 

 Union Observatory. 



Failing health rendered it impossible for Mr. Franklin-Adams 

 to complete the two projects that he had in mind: the pul)lica- 

 tion of the photographs, and the statistical discussion of the 

 number of stars of different magnitudes in different parts of 

 the sky. It was arranged that the statistical discussion should 

 be made at Greenwich, and the plates, 20 G in number, and 

 each about sixteen inches square were presented to the lioyal 

 Observatory. 



Daring the last three or four years, sample counts have been 

 taken of these 206 plates, on small areas imiformly distributed 

 over them, and. the number of stars in these areas have been 

 carefully ascertained, the stars being classified according to their 

 brightness. This has necessitated a great amount of very 

 heavy work, into the details of which it is not necessary now 

 to enter. The actual briglitness of tliese stars compared on a. 

 uniform plan with other stars over each part of the sky has 

 been determined, and in this way the number in the whole sky 

 has been estimated from the sample counts. Counts have been 

 made from 5,000 selected regions, and the number of stars in 

 the whole sky estimated for each magnitude down to the 17th, 

 the table given above being based upon the results of these 

 counts. The total number of stars down to the iTth magnitude, 

 approximately 55,000,000, is therefore derived from this process 

 of sample counts on the 206 plates covering the entire heavens, 

 which the enter[)rise of the late Mr. Franklin-Adams lias 

 provided. 



A consideration of the table will show that, as we pass to. 



