OCTOBEB 21, 1910] 



SCIENCE 



543 



solar spectrum and new measurements accord- 

 ing to the international system shall be taken 

 as soon as possible. 



Professor Hartmann made the following 

 suggestions, which were not accepted by the 

 committee, but in accordance with his request 

 are appended to the report of the committee : 



1. In all cases, where owing to special rea- 

 sons, wave-lengths are measured and published 

 according to the " Rowland system," those 

 wave-lengths shall be used as Standards which 

 are calculated from the recent interferometer 

 measurements, taking as the wave-length of 

 the red cadmium line A6438.7098. (Such 

 standards have been published by Hartmann 

 in the Physih. Zeitsch., vol. 10, p. 123, and 

 others will be published in accordance with 

 the best measurements.) 



2. In order to avoid misunderstanding in 

 the publication of wave-lengths, the system of 

 standards used in each ease shall be indicated 

 by using special symbols after the wave- 

 lengths. The following method is proposed : 



(a) " M." " The Michelson System," based 

 upon 6438.4722 M., as the wave-length of the 

 red cadmium line. 



(b) " C." " The International System," 

 based upon 6438.4696 C, as the wave-length of 

 the red cadmium line, the value adopted by 

 the third International Conference. 



(c) " E." " The Rowland System," as de- 

 fined above. 



At the second session the following reports 

 were presented: 



Measurement of Solar Radiation: Mr. Abbot. 

 Sun-spot Spectra: Mr. Fowler. 

 Eclipses : M. le Comte de la Baume Pluvixel. 



Mr. Abbot discussed the measurement of 

 solar radiation under the following headings : 

 (1) Solar Constant Work by method of 

 Langley, (2) Solar Variation, (3) Simplified 

 Methods for Solar Constant Work, (4) Pyre- 

 heliometry, (5) Sky Radiation and Cloudi- 

 ness, (6) Distribution of Radiation over the 

 Sun's Disk, (7) Mount Whitney Station. 



The committee on sun-spot spectra closed its 

 report with the following resolutions, which 

 were adopted by the conference : 



1. That the report of the work of the sun- 



spot spectrum committee and of the coop- 

 erating observers, be printed in the next vol- 

 umes of the Transactions of the Solar Union, 

 in full or in abstract as circumstances may 

 determine. 



2. That notwithstanding the progress of 

 photographic work, visual observations of spot 

 spectra should be continued, and that the com- 

 mittee should be reappointed to continue the 

 organization of this work. 



3. That in view of our increased knowledge 

 of spot spectra, the committee be authorized 

 to prepare and circulate a revised and ex- 

 tended scheme of visual observations. 



4. That in view of the fact that several ob- 

 servers have prepared manuscript catalogues 

 of several thousands of lines in the photo- 

 graphic spectra of sun-spots, it is desirable to 

 have such catalogues collated by those who 

 made them, in such manner that all the avail- 

 able data should be collected in a single cata- 

 logue. 



5. That it is desirable that, for the use of 

 visual observers, the separate sections of the 

 new photographic map of the sun-spot spec- 

 trum should not exceed 60 centimeters in 

 length, and should be on a scale of 5 mm. to 

 the Angstrom. 



The eclipse committee, through its secre- 

 tary, M. le Comte de la Baume Pluvinel, 

 briefly recounted the experiences of the Flint 

 Island expedition of 1908 and the Tasmanian 

 expedition of 1910. The committee under- 

 takes to further cooperation among eclipse ob- 

 servers by distributing observing programs to 

 avoid duplication of work, and by aiding in 

 the loaning of apparatus for eclipse observa- 

 tions. It was recommended by the commit- 

 tee that the direction of measurement of posi- 

 tion angles around the sun's limb be from 

 north to east. The recommendation was 

 adopted by the conference. 



Father Cirera presented the following re- 

 port: 



1. La communication de M. le Secretaire 

 sur les eclipses a ete presentee par moi a le 

 Section d'Astronomie de I'Association Es- 

 pagnole pour I'Avancement des Sciences. On 



