154 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1920. 



5. The distribution of energy in the solar spectrum had been closely 

 determined, and thereby our knowledge of the sun's temperature and 

 nature had been materially increased. 



6. Various by-products of the investigation, such as relating to the 

 transparency of the atmosphere under different circumstances of 

 humidity and haziness and for different altitudes from sea level up 

 to the level of Mount Whitney, the study of the dependence of the 

 temperature of the earth on radiation, the temperature of sun spots 

 as compared with other parts of the sun's disk, and many other 

 matters, had been investigated. 



BASSOUR, ALGERIA. 



By far the most interesting of these results of the investigation 

 was the supposed short-period variability of the sun. Although the 

 values of the " solar constant " did not appear to depend upon the 

 altitude of the observer above sea level, yet the apparent variations 

 of the sun were so little greater than the probable errors of the 

 observations that it seemed essential to strengthen the discovery of 

 the solar variability by some other independent check. The most 

 obvious procedure was to equip another observing station in a favor- 

 able region far removed from Mount Wilson, and to carry on for a 

 considerable period of time duplicate measurements of the " solar 

 constant " at the two stations. 



Preparations were made to go to Mexico for this purpose, but the 

 breaking out of revolution there made it undesirable to set up the 

 station in Mexico. Accordingly, the expedition was diverted to 

 Algeria, in North Africa, a country under the stable government of 

 the French, where good conditions with regard to cloudlessness might 

 be expected. The expedition went forward in 1911, employing the 

 same apparatus that had been used on Mount Whitney, although 

 with decided improvements in many respects. The expedition was 

 in charge of the writer, who was accompanied by Mrs. Abbot and 

 assisted by Professor Brackett, of Pomona College, California. 

 After discussion with the United States vice consul at Algiers, the 

 director of the observatory there, and others, a site was selected at a 

 little hamlet called Bassour, about 50 miles south of Algiers. 



With the exception of a few French neighbors, the people in the 

 vicinity were all Arabs, and there was a great deal of interest in 

 observing their customs and methods of working, which are nearly 

 identical with those of the times of Abraham. The most important 

 Arab in the neighborhood was a caid, who took a great interest in 

 our work and assisted it by keeping his curious neighbors from inter- 

 rupting it. 



As a boy I had sometimes wondered at the story in the Book of 

 Ruth, which says that Boaz slept upon his threshing floor. On our 

 farm in New Hampshire we sometimes threshed small lots of grain 



