156 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1920. 



As shown by the illustration, figure 2, the sun is not equally 

 bright along its diameter, but falls off rapidly toward the edges of 

 the disk. This contrast in brightness between the center and edge 

 of the solar disk is much greater for violet and ultra-violet rays than 

 it is for red and infra-red ones, but what is particularly interesting, 

 the contrast of brightness which had been determined in Washing- 

 ton in 1907 was found to be less when it was redetermined at Mount 

 Wilson in 1913. Not only was this result found, which confirmed 

 the existence of the variability of the sun in the term of years, but 

 the experiments at Mount Wilson show that the contrast of bright- 

 ness varied from day to day in association with the variations of the 

 "solar constant." This result, taken in connection with the experi- 

 ments in California and Algeria in 1911 and 1912, fully confirmed the 

 existence of the short-period variations of the sun. 



VISIT TO AUSTRALIA. 



In most countries the seat of government is fixed at some promi- 

 nent city, but the United States and Australia are alike in that a 

 special place was selected to build the capital. In the United States, 

 although the streets were well laid out, no particular care appears 

 to have been taken in regulating the character of buildings in Wash- 

 ington, so that, apart from the great public spaces and some fine 

 buildings for Government purposes, the city presents the ordinary 

 up and down happy-go-lucky appearance of almost all of the Amer- 

 ican cities. In Australia, however, a competition was established to 

 plan a model city for the new capital at Canberra. Amongst the in- 

 stitutions embraced in the plan of public buildings was to be an ob- 

 servatory. In 1914 the British Association for the Advancement of 

 Science met in Australia. In connection with it, various scientists 

 were invited by the Australian Government, and amongst them the 

 writer was asked to attend and to take the opportunity to present to 

 the Government and to Australians and others interested the story 

 of the solar researches which have been mentioned above, in order 

 that if possible plans might be made for the inclusion of the " solar 

 constant" work in the program of the proposed new Government 

 observatory at the capital city of Canberra. 



Accordingly, the writer sailed to Australia in 1914, but as he 

 arrived at Sidney came the news of the outbreak of the great Euro- 

 pean war. Accompanied by the astronomer royal of England, Sir 

 Oliver Lodge, the former premier of Australia, and other men of 

 great weight, the writer waited upon the premier at Melbourne and 

 presented the case of the " solar constant " work as had been ex- 

 pected. But it was felt that owing to the unexpected participation 

 of Australia in a great war the time was unpropitious for promoting 

 any new projects, although much interest was taken in the work de- 



