famous Asaph Hall, astronomer, who had studied for a short time at Ann Arbor under Brünnow (see p. 445) . Hall, Jr., came to the University from the United States Naval Observatory, where he had been assistant astronomer since 1882, with the exception of four years spent at Yale University.
The announced courses of instruction were continued with very slight change; they included General Astronomy, Spherical and Practical Astronomy, Theoretical Astronomy, and an extended practical course, Astronomy 9, to which only students who received special permission were admitted.
The new Director, whose father had urged him to do meridian-circle work when he came to Michigan, took an immediate interest in the condition of the instruments. Watson had not made regular use of the meridian circle. It was now put into good condition and re-examined for division errors to test Brünnow's results. Brünnow's elaborate series of observations of the Bradley stars made with this instrument had been taken to Europe. Hall resumed work on the Bradley stars, including some for latitude determination and latitude variation.
The need for regular publication of astronomical investigations conducted at the University was one which Hall recognized soon after he came to Ann Arbor. In the way of records very little could be found. Brünnow's Astronomical Notices, begun in 1858, had been discontinued in March, 1862. Articles on the subsequent observation of comets and asteroids made here with the twelve-inch telescope by Brünnow, Watson, Schaeberle, Campbell, and Hussey were hard to find, since they were scattered through various astronomical and other scientific publications. Although Hall wished to establish a series of publications and succeeded in producing part of a volume, articles from the Observatory during his administration continued to appear in outside periodicals, chiefly the Astronomical Journal. Most of these writings were by Sidney Dean Townley (Wisconsin '90, Sc.D. Michigan '97).
A paper which Hall presented at the eighth annual meeting of the Michigan Academy in March, 1902, was published in 1904 by that organization, together with a reprint of pages 37-88 labeled "Transactions of the Detroit Observatory, University of Michigan, Part I. Determination of the Aberration Constant from Zenith Distances of Polaris Measured with the Walker Meridian Circle." It contained a historical introduction regarding the Observatory and a brief section on the latitude and longitude, giving the values previously adopted. Then followed a general description of the Walker meridian circle and specific details regarding its various parts, including a redetermination of the errors of the divisions of the circles. An extensive series of observations on Polaris from April, 1898, to February, 1901, was recorded, and the data were combined by the method of least squares. This involved a large amount of computing, for which a grant was received from the Bache fund of the National Academy of Sciences. The value of the aberration constant obtained was 20."683; this was rather large compared with the value 20."47, which was adopted by the Paris conference of 1896 and is still in use (1942).
The determination of the latitude of the Walker meridian circle was inherent in Hall's method of finding the aberration constant. He obtained +42°16' 48."78; from Hall's meridian-circle observations Harriet Bigelow (Smith '93, Ph.D. Michigan '04) has obtained a value of +42°16'48."76; the present adopted value is +42°16'48."70.
Hall's work on the aberration constant was the last he published at the Detroit
