OF ARTS AND SCIENCES. 325 



The new building, the instrument, and the fund which renders it 

 possible to carry on astronomical observations, are the gifts of the 

 same gentleman, the Hon. David Dudley Field, of New York City, 

 well known in all civilized countries for his services to international 

 jurisprudence. 



The series of observations here presented is, it is hoped, the begin- 

 ning of a large catalogue of stars. It is published in this form in 

 order to set forth some principles, which, as I believe, represent the 

 present state of practical astronomy with regard to the construction 

 of a secondary catalogue ; and to interest other observers in the appli- 

 cation of these principles. 



These observations are also intended, in connection with earlier 

 ones upon the same stars, to meet a definite practical necessity for an 

 extensive catalogue of polar right ascensions for various purposes 

 of practical astronomy and geodesy. There are many observations 

 whose final discussion, especially with respect to systematic corrections, 

 will need to be based upon a combination of such catalogues as the 

 one here presented ; and the need of more such, especially for the 

 latest epochs, is sensibly felt by all who have been obliged to make 

 time-observations in the field for telegraphic longitudes. This is 

 especially true in our Western Territories ; the telegraphic communica- 

 tions are often precarious, and an accurate catalogue which enables the 

 astronomer to determine his time, by portable instruments, in half an 

 hour, with the precision of a fixed observatory, would often be of great 

 assistance towards economy of labor. 



I have already published such a catalogue of polar right ascensions 

 for 1865, and its repetition on a more extensive scale is now, I think, 

 timely. Certain unsolved questions relating to personal equation will 

 also be advanced towards a solution by the speedy publication of the 

 materials here collected. 



The method of observation is the following. 



At the beginning of an evening's work the time is determined, as 

 well as the deviation of the instrument from the pole, Bessel's n, by 

 stars from the Berlin Jahrbuch. These observations are followed 

 by a set of observations of stars to be determined, and the evening's 

 work concluded by other stars from the Berlin Jahrbuch. From the 

 beginning I have taken pains that every determined star should be 

 preceded and followed by enough standard stars to make the interpola- 

 tion of the n perfectly certain, and to give the n a weight of at least 

 two observations of the star to be determined. Latterly, as the pre- 

 cision of the observations has become greater, I have taken similar 



