240 CARNEGIE INSTITUTION OF WASHINGTON. 



On the other hand, Mr. Roy has noted a decided effect of the nature 

 of lost motion. On a number of occasions, when there has been a 

 decided rise or fall of temperature, the collimation has remained prac- 

 tically stationary'. The same was found to be the case when the obser- 

 vations were taken at or immediately following the maximum temper- 

 ature of the day. The collimation appears to remain constant when 

 the temperature fluctuates within a range of about 22° C. Under this 

 hypothesis change in collimation would be dependent upon the extreme 

 daily range of the temperature. Whenever the temperature varies 

 sufficiently to take up the lost motion there is a change in the collima- 

 tion. It is only at such times that a gradient or lag term would 

 become effective. Observations have been planned to thoroughly 

 investigate the matter. 



Mr. Jenkins has published the results of a survey of the San Luis 

 photometric determinations for the purpose of noting large discrep- 

 ancies in the observed values. The list contains stars for which the 

 San Luis observations are discordant; stars whose magnitudes as 

 measured at San Luis differ considerably from those given by Harvard, 

 and a few others whose magnitudes differ with Gould's. While part 

 of the discordances may be attributed to abnormal measurements, 

 there is considerable probability that some of these stars are variables. 



The printer's manuscript for the zone catalogue of observations 

 undertaken during the years 1896 to 1900 has been thoroughly checked. 

 The comparison with other catalogues has been completed and proper- 

 motions computed for all stars where this motion amounts to 10" per 

 century. Many stars with an indicated motion slightly in excess of 

 this limit were excluded because of large probable error. Of the more 

 than 700 proper-motions, about 100 were either under 10" or so slightly 

 above that limit as to indicate that they may eventually prove to 

 fall under the limit. With few exceptions stars were not considered 

 if they had but one authority antedating the Albany observations. 



APPARATUS. 



The new Riefler clock, No. 218, has been secured and mounted in 

 position. It is of the latest type, free escapement, nickel-steel pendu- 

 lum with compensation of temperature and its stratifications, electric 

 winding, and arranged to break the chronograph circuit every second. 

 This clock will in the future serve as the standard clock. 



The system for temperature control of the clock-room has been 

 installed. Several difficulties in the proper operation of the sj^stem 

 have been overcome, but it is still desirable to change the operative 

 power of the automatic switch employed in the system. The thermo- 

 graph records of the clock vault indicate a very small variation of 

 temperature, the record being practically a straight line. 



