174 REPORTS ON INVESTIGATIONS AND PROJECTS. 



(24) The extent and elements of the Scorpius-Centaurus and Perseus 

 groups have been investigated, and parallaxes have been derived for stars 

 in these groups having a sensible proper-motion. 



(25) A preliminary investigation has been made on the distances from 

 our system attained by the star-streams. 



(26) It has been found that a number of stars in Vela probably form a 

 local group. 



(27) All local groups of stars, for which the necessary data are available, 

 have been shown to move in space nearly parallel to the Milky Way. 



(28) It appears to be true that the more distant stars are redder than the 

 nearer ones, either because of absorption of light in space or through an 

 influence of the absolute luminosity. 



(29) Photographs of the very short spectra of faint stars, obtained with 

 a large grating attached to the 60-inch reflector, afford a means of determin- 

 ing their effective wave-length, which is a measure of their color. 



(30) A continuation of the investigation of the effect of pressure on 

 furnace spectra confirms the results obtained last year and shows that varia- 

 tions in temperature and certain changes in the physical and chemical con- 

 dition of the vapors are without appreciable effect on the displacements for 

 a given pressure. 



(31) There is an important difference in the structure of arc and furnace 

 lines, which may affect their susceptibility to pressure displacement. 



(32) The study of metallic spectra between A 2500 and A 7500 at various 

 temperatures in the electric furnace has disclosed many new groups of lines, 

 some of which are very susceptible to temperature change. 



(33) A comparative study of arc and furnace lines shows that the vari^ 

 ations of relative intensity in different parts of the arc correspond closely 

 with those observed in the furnace at different temperatures. 



(34) The relative richness of arc and furnace spectra is very different 

 for different elements. 



(35) A study of photographic processes emphasizes the great obscurity 

 of the subject and the dependence of the plate manufacturers upon empirical 

 methods. Certain promising lines of research are pointed out in this report. 



STAFF. 



The Director returned to his regular duties in October 191 1, after an 

 absence of 16 months on account of illness. His special researches of the 

 present year include the study of the magnetic field and the theory of sun- 

 spots, the spectrum of the chromosphere, and attempts to detect the general 

 magnetic fields of the sun and certain nebulae. During the Director's ab- 

 sence Mr. Adams served as Acting Director, carrying on all departments 

 of the Observatory in the most efficient and satisfactory manner. He has 

 also continued without interruption his work in charge of the Department 



