DEPARTMENT OF MERIDIAN ASTROMETRY. 151 



(B to B.J, and of these 472 have Galactic latitude less than 30 , and 244 

 have latitude less than 10°. 



This and other indications seemed to render it necessary that in our fur- 

 ther examination of evidences of systematic motion we should take into ac- 

 count the principal types of stellar spectra. 



Furthermore, we find evidence which seems to indicate, on the part of the 

 larger motions at least, a tendency in those motions to have comparatively 

 small inclinations to the plane of the Galaxy. 



We are now proceeding to test these and other points bearing upon our 

 general hypotheses. The necessity of pushing reductions of the observations 

 reported from San Luis greatly restricts the amount of time we can devote 

 to these important researches. In fact, it is becoming more and more evident 

 that the facts of observation which we are hoping to accumulate in the larger 

 General Catalogue will soon be urgently needed to establish more accurately 

 what degree of confidence shall attach to various promising hypotheses that 

 are constantly cropping up in relation to the mechanism of the stellar uni- 

 verse, for the proper examination of which the existing material is showing 

 itself to be inadequate in the number of stars. 



OBSERVATIONS AT SAN LUIS. 



In the Year Book for 1909 (pp. 154-158) some account was given of the 

 work of installing the Olcott meridian-circle in San Luis, Argentina, and of 

 the observations thereupon begun April 6, 1909. 



The remarkable rate of observations reported as prevailing up to the close 

 of the record in August 1909, so far from falling off, became even somewhat 

 accelerated. At the end of the first full year of observations, April 1, 19 10, 

 more than 60,000 observations had been obtained. The latest date for which 

 I have a report of the count is August 1, 1910. At that date the total for 

 16 months, which includes observations of the nadir, was, in round numbers, 

 78,000, of which the share of each observer at the telescope was approx- 

 imately as follows: R. H. Tucker, 17,700; A. J. Roy, 19,800; W. B. Varnum, 

 20,400; M. L. Zimmer, 11,000; R. F. Sanford, 9,100. 



The instrumental circumstances of observation are conveniently designated 

 as follows : B and W indicate whether the clamp of the instrument was east 

 or west. Reversal took place about once a month. A or B indicate whether 

 the circle A (next the clamp) or B, respectively, was employed in observa- 

 tion. Alternation in the employment of circles took place about midway be- 

 tween reversals. The 78,000 observations were almost equally distributed in 

 the four circumstances of the instrument: AB, AW, BB, and BW. 



The observers usually worked in two shifts on each night, each consisting 

 of an observer at the telescope and another at the microscopes. Sometimes, 

 in the crowded parts of the list, a third assistant was employed in making the 

 settings. Up to August 1, 563 series had been observed on 369 nights. The 

 average number of observations in each series was a little under 140. It was 



