Correspondence regarding photographic magnitudes in relation to astrographic charts:

Correspondence with E.C. and W.H. Pickering of Harvard College concerning various aspects of astrographic charts and the determination of photographic magnitudes, 1909-1912, with Circular No. 150 on standard photographic magnitudes of the polar sequence and photographs of the north polar sequence stars.

Correspondence with various individuals concerning photographic magnitudes, 1911, with various Greenwich memoranda, including the determination of Pickering's sequence using astrographic methods; W.E. Cooke of Perth on new imperial scales; Sir David Gill on the magnitude of the Pleiades, with a photographic chart; J.C. Kapteyn on standards for magnitudes; F.H. Scarrs, Mount Wilson, writing to S. Chapman and P.J. Melotte, assistants, on their determination of the polar sequence; Professor Schwartschild of Potsdam on stellar magnitudes; J.C. Kapteyn on stellar magnitudes; J.A. Parkhurst, Yerkes, on stellar magnitudes; and H.H. Turner on star magnitudes.