[1] A dissertation submitted to the Faculty of the Ogden Graduate School of Science of the University of Chicago in candidacy for the degree of Doctor of Philosophy.

[2] Nucleus is eccentric and undefined on the photograph, hence the photographic position is probably in error by several seconds of arc.

[3] Mean of the positions given in Vols. III and IV. N.G.C. 7621 is 5ˢ.4 preceding, and 1′ 49″ south of 7623. There is a double star in the position published in the Strassburg Annals.

[4] Mean of the positions given in Vols. III and IV. N.G.C. 7621 is 5ˢ.4 preceding, and 1′ 49″ south of 7623. There is a double star in the position published in the Strassburg Annals.

[5] Mean of the positions given in Vols. III and IV. N.G.C. 7621 is 5ˢ.4 preceding, and 1′ 49″ south of 7623. There is a double star in the position published in the Strassburg Annals.

[6] Mean of the positions given in Vols. III and IV. N.G.C. 7621 is 5ˢ.4 preceding, and 1′ 49″ south of 7623. There is a double star in the position published in the Strassburg Annals.

[7] [See Plate IV], enlarged from negative R 3352, taken with 120ᵐ exposure on February 26, 1916. The numbers were marked on only those nebulae which promised to be readily visible on the engraving, and which were separated enough to give room for inscribing the number. The B.D. stars are designated by letters, for which the key is as follows.

[8] Popular Astronomy, 24, 111, 1916.

[9] Journal of the R.A.S., Canada, 10, 134, 1916.