542 



SCIENCE 



[X. S. Vol. XXXII. No. 825 



morning the laboratory, shops and offices of 

 the Mount Wilson Solar Observatory were 

 inspected. In the afternoon the members and 

 their friends were entertained at a garden 

 party given by Mr. and Mrs. Hale at their 

 home. On Tuesday the ascent of Mount Wil- 

 son was made, by some in carriages via the 

 Mount Wilson Toll Road from Pasadena, by 

 others on saddle animals from Sierra Madre. 

 Including the staff of the Mount Wilson Ob- 

 servatory, tke entire party making the ascent 

 numbered about one hundred. Forty-two 

 delegates from abroad, representing ten differ- 

 ent nations, were present. 



The sessions of the conference were held in^ 

 the museum building of the observatory on 

 the mornings of August 31, September 1 and 

 September 2, with an afternoon session on the 

 last day. The afternoons were for the most 

 part given up to committee meetings and an 

 inspection of the equipment of the obser- 

 vatory. 



Professor Pickering occupied the chair at 

 the session of the first day. Professors Camp- 

 bell and Frost on the second and third days, 

 respectively. 



In his opening address Professor Hale con- 

 sidered the following salient points: 



1. Emphasis of the union's function as a 

 stimulator of research. 



2. Benefits of formal cooperation as shown 

 in the adoption of standards of wave-length. 



3. Sun-spot spectrum map. 



4. Description of the 150-foot tower tele- 

 scope of the Solar Observatory and its equip- 

 ment, when used for spectrographic observa- 

 tions and as a spectroheliograph. 



5. The observation and interpretation of 

 various groups of phenomena observed in sun- 

 spots and in their spectra: sun-spot lines ap- 

 pearing as triplets or as quadruplets; lines 

 asymmetrical in intensity or in separation; 

 variations of intensity of magnetic field as 

 shown in lines of the same and of different 

 elements; apparent rotation of plane of polar- 

 ization of the light by its passage through the 

 spot vapors ; methods of mapping the magnetic 

 field in and around spots; unipolar, bipolar 

 and multipolar vortices around spots. 



6. Cooperative work — (a) with spectrohelio- 

 graphs, and the importance of the Ha line for 

 this work; (b) in connection with eclipse ex- 

 peditions. 



The remainder of the first session was occu- 

 pied by the presentation and discussion of the 

 reports of the executive committee and of the 

 committee on wave-lengths. 



Professor Kayser presented the last-named 

 report. The following recommendations were 

 incorporated in it and were separately adopted 

 by the conference: 



1. In the region of the spectrum, in which 

 three independent measurements by the inter- 

 ferometer method of the lines of the iron arc 

 are available, i. e., between A4:282 and A6494, 

 the arithmetical mean of the three measure- 

 ments shall be adopted as definite interna- 

 tional standards of second order, provided 

 there is sufficient agreement between them. 



2. The committee be given authority to pub- 

 lish these standards as soon as possible. 



3. For the part of the spectrum in the neigh- 

 borhood of A5800, where the number and char- 

 acter of the iron lines is not satisfactory, the 

 committee propose the use of barium lines as 

 additional standards. 



4. The laboratories or observatories possess- 

 ing first-rate concave gratings are invited to 

 determine by interpolation as soon as possible 

 standards of the third order in the spectrum 

 of the iron-arc within the above range of 

 spectrum (i. e., A4282 to A6494). 



5. The measurement of standards of the sec- 

 ond order shall be extended to shorter and 

 longer wave-lengths, and the arithmetical 

 mean of three independent determinations 

 shall be adopted as secondary standards. 



6. Standards of the third order shall then 

 be obtained from them in the manner indi- 

 cated. 



1. The above system of standards shall be 

 called the international system, the unit on 

 which it is based being called the interna- 

 tional unit (I. U.) as defined by the confer- 

 ence of 1907. 



8. It is very desirable that in different labo- 

 ratories possessing concave gratings of the 

 first quality photographs of arc, spark and 



