34 REPORT OF THE SECRETARY. 



have been pleased to learn that no part of the Government exhibits has 

 excited more popular interest there. 



Congress at its last session took up the important question of the 

 definitive arrangement of streets in the vicinit}' of the Zoological Park, 

 and established, b}^ law, two such thoroughfares, one on the south- 

 eastern, the other on the western side of the park. Two comparatively 

 narrow strips are thus left between these roads and the park boundary, 

 and it would be of great advantage if these strips could be added to 

 the park. Attention has been called to this matter in previous reports, 

 and 1 have again submitted to Congress an estimate of the sum required 

 to effect the necessary purchase, 



I can, in conclusion, repeat my statement that the park is fultilling 

 more amply than ever the objects for which Congress founded it, 

 "the advancement of science and the instruction and recreation of the 

 people." 



ASTROPHYSICAL OBSERVATORY. 



In my last year's report I stated that it was probable that the radia- 

 tion of the sun after absorption by the earth's atmosphere as received 

 at Washington, appeared to have fallen off' l)y 10 per cent, and 1 added 

 that there had possibly been a decrease of the solar radiation itself 

 since the early part of the year 1903. I observed in this connection 

 that there seemed renewed promise of progress toward the\foretelling 

 by such means of the remoter changes of weather which affect harvests, 

 which was one of the great aims had in view in the foundation of the 

 observatory. 



With the aid of the large horizontal telescope and the apparatus 

 for obtaining distinct vision introduced by me and described in my 

 last report, and more fully in that for the present year, I have con- 

 tinued these investigations, particularly with reference to the increase 

 or diminution of the original solar radiation, apart from that absorbed 

 by the earth's atmosphere, and by means which are unaffected by that 

 absorption. These observations, independent of any theory upon the 

 subject, indicated that at the time of the observation in the last report 

 this radiation fell oft' at the source of energ}' in the sun, and that 

 changes in the transmissibility of the solar atmosphere were a possible 

 cause of at least a part of the effect observed on the earth. The amount 

 by which this solar radiation was diminished, as determined at the 

 source in the sun itself, appears to be in general accord with the state- 

 ments of meteorological observatories as to the changed temperature 

 at the earth's surface. 1 do not, however, venture to make the state- 

 ment that the diminution was unquestionably due to a change in the 

 solar envelope as an established fact, until further observations have 

 been made, while I still call attention to the high importance of addi- 

 tional study of the question. 



