Yoh. 6, 1920 INTERNATIONAL ASTRONOMICAL UNION 
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1. To advise as to what eclipse problems are most worthy of attack, 
and what equipment is needed for successful work. 
2. For the eclipse of 1923, to collect well in advance all available in- 
formation regarding possible eclipse sites, weather probabilities, trans- 
portation facilities, living conditions, etc. (The Mexican Meteorological 
Service has already been communicated with in regard to the eclipse of 
1923.) 
3. To publish such information and eclipse computations well in ad- 
vance. 
4. To advise intending observers as to location so as to secure a wide 
distribution of stations. 
5. To gain information regarding the apparatus that is available at 
different observatories, and to arrange as a central clearing-house for the 
loan of apparatus to intending observers who have not adequate facilities. 
A discussion is given of the various eclipse problems under the headings : 
Photography of the corona. 
What is the corona? 
What causes the corona? 
Motion of the corona. 
Polarized light in the corona. 
Brightness of the corona. 
Spectrum of the corona. 
Wave-lengths of coronal lines and rotation of the corona. 
Flash spectrum. 
Einstein effect. 
Times of contact. 
Other eclipse problems. 
Movie camera. 
S. A. MiTCHKivL, Chairman, E. E. Barnard, H. D. Curtis. 
REPORT OF THE COMMITTEE ON STANDARDS OF WAVE-LENGTH 
1. It is recommended that the International Astronomical Union 
appoint at the earliest practicable date, a committee whose functions shall 
be essentially the same as those of the Committee on Wave-Lengths of 
the International Union for Cooperation in Solar Research. 
2. The primary standard. — ^The remarkable sharpness of the red Cad- 
mium line, the extraordinary skill with which the meter was evaluated in 
terms of this wave-length, and the final definition of the angstrom, as an 
arbitrary unit, by the international Solar Union at Paris in 1907, would 
seem to place the primary standard almost beyond the range of question. 
However, the recent perfection of a new method for making end-stand- 
ards of length, the comparative ease with which the optical length of these 
end-standards can be determined, and the possible superiority of some other 
