22 CARNEGIE INSTITUTION OF WASHINGTON. 



The extensive computations essential in the derivation of the great 

 number of stellar positions observed at the temporary observatory at 

 San Luis, Argentina, are going forward at a favorable rate, so that the 

 inclusive catalogue of precise positions for stars in both hemispheres 

 may be expected in due time. Some instructive results of these 

 computations, showing the stability of the San Luis meridian mark 

 (mire), the diurnal variation of the clock corrections, and the changes 

 of personal equation for day and night observations are given in the 

 report of the Acting Director. 



As in most lines of fruitful research, the work of this department 

 is noteworthy for its by-products, or for contributions it is making 

 to allied lines of inquiry. Obviously, a first requisite to a knowledge 

 of stellar motions lies in precise determinations of stellar positions 

 at different epochs. The so-called proper motions of stars are thus 

 brought to Hght, and from these it is jDossible to determine also the 

 motion of our solar system. But now comes the surprising discov- 

 ery that these proper motions, hitherto supposed to be of a random 

 character, are of a systematic nature dependent in large degree, 

 apparently, on the stage in evolution any individual star has reached 

 and on the group to which it belongs. A new and peculiarly fas- 

 cinating field is thus opened to astronomers of all Idnds, and the 

 by-products referred to seem destined to prove not less important 

 than its primary object in positional astronomy. The world of 

 astronomy, however, is anxiously awaiting the attainment of this 

 object, as is well shown by the fact that the preliminary catalogue 

 issued by the department three years ago is already out of print. 



One of the reasons which helped seven years ago to determine the 

 location of this laboratory was found in the expectation that several 



The Nutrition hospitalswould be erected in the near vicinity. This 

 Laboratory. expectation lias now been realized by the completion 

 during the past year of the Peter Bent Brigham Hospital, the Collis 

 P. Huntington Memorial Hospital, and of two hospitals for infants 

 and children respectively. The environment and the opportunities 

 for securing pathological subjects as well as clinical cooperation and 

 counsel are therefore highly favorable for the researches undertaken 

 by this estabhshment. That it has entered a fruitful field of activity 

 is well attested by the wide interest shown in its publications already 

 issued, by the desires of experts at home and abroad to learn of the 

 ways and means employed, and by the duplication in laboratories 

 of other countries, as well as in those of America, of the apparatus 

 developed. 



