INTRODUCTION 
V 
of standard stars. In order to facilitate the selection of these stars it was apparent 
that the safest and most economical plan would be to form a card-catalogue of 
all the stars contained in what may be termed catalogues of precision of a date 
of observation earlier than the middle of the nineteenth century. Those stars 
contained in a large number of these earlier catalogues would be more useful than 
others for ascertaining the systematic corrections of these same catalogues, both 
because of the frequency of their use and also, since the motions of such stars can 
be more precisely computed, they make better standards. This course, once 
adopted, rapidly led to extensions of the original plan. After the older catalogues 
of observation had been drawn off upon the cards (except fainter stars of Groomb 
io and Radcl 45), including all the important ones of an observation-date earlier 
than 1855, the original intention had been not to include the later catalogues entire, 
but to transcribe only for stars found in the earlier catalogues. But it now seemed 
that the inclusion of all stars down to the seventh magnitude, though it would much 
increase the labor of transcription for the remaining catalogues, might later prove 
to be very desirable in view of the development of our plans then going on; 
and that the collection so formed would, in any case, constitute an asset of value. 
This extension of the list was effected slowly and rather imperfectly at first, but 
subsequently was improved. In its present state the card-catalogue contains about 
25,000 stars. There are included all that are noted in the Bonn Durchmusterung, 
Potsdam Photometry , Harvard Photometry , or the Uranometria Argentina as of the 
magnitude 7 M o or brighter. 
The inclusion in our list of stars down to the seventh magnitude, in addition to 
all stars occurring in certain catalogues of precision of the first half of the nineteenth 
century, was primarily due to the desire of selecting stars upon some simple criterion 
which should give promise at the same time that the stars so selected would be: 
1. On the whole, nearer our system than the stars not included. 
2. As a rule, better observed than the others. 
3. For certain technical reasons, not chosen with reference to the amount 
of proper-motion any particular star may have. 
In this collection was presented an almost irresistible temptation to ascertain, 
so far as possible, the motion of each star therein, and eventually to produce an 
extensive general catalogue of the positions and motions of these 25,000 stars. 
Meanwhile we were at work upon the 11 Catalogue of 627 Principal Standard 
Stars,” already mentioned, and upon its subsequent extensions, resulting for the 
time being in computed positions and motions for about 2500 so-called Standard 
Stars. 
About that time, in 1903, the Carnegie Institution of Washington had come to 
the aid of this work; and three years later had so far increased its interest as to 
develop this project into its Department of Meridian Astrometry, with liberal 
appropriations for carrying out the construction of the proposed large general 
catalogue (including about 25,000 stars) to which allusion has already been made. 
To complete this extensive work, including heavy tasks in meridian-observation 
as planned, would evidently be the labor of many years. The question naturally 
came up whether it would be necessary to defer the publication of all catalogue- 
