466 



KNOWLEDGE. 



December, 1910. 



numerous 

 Professor 



delegates 



Hale, 



July 17, 1905, 17" 56'". Low- Level Cal- 

 cium Flocculi Slit Set on Hi (X3965) 

 Sun's Diameter =0.28 meter. 





r; 





TIk' report of the 

 given hy Professor Schustt 



Professor Kayser pre- 

 sented the report of the 

 Committee of wave 

 lengths, suggesting the 

 adoption of three hun- 

 dred and seventy - one 

 standard wave lengths, 

 mosth' of tile iron spec- 

 trum. 



Mr. Abbott jjresentetl 

 the report on the meas- 

 urement of Solar radia- 

 tion. The most probable 

 value of the Solar Con- 

 stant of radiation appears 

 to be about 1'92 calories 

 per square cm. per 

 minute. 



Professor Fowler pre- 

 sented the report of the 

 committee of Sun-spot 

 observations, one result 

 of which is, that the spot 

 spectrum is found to be 

 as constant as the Fraun- 

 hofer spectrum itself. 



Professor Newall spoke 

 ol the possibility of using 

 plane gratings for measuring the 

 tertiar\' standards, whilst Professor 



and giving a short ^address, 

 unfortunately, was unable, on 

 account of illness, 

 to take an active 

 part in the meet- 

 ings. In his address 

 he spoke of the use 

 I if the Conferences 

 and of their stim- 

 ulation to research: 

 also on the needs of 

 tertiary standards. 

 and the preparation 

 of a sjjectrum map 

 on a large sc;de. 

 He also spoke of 

 the new tower tele- 

 ■-cope and com- 

 bined spectrograph 

 .iiul spectrohelio- 

 L;raph, illustrated 

 m this article. 



Tlie sessions of 

 the Conference 

 then formalh' be- 

 gan, and the reports 

 of the \- a r i o u s 

 committees were 

 received. 

 Executive Committee was 



20, 1905. 5" 18"'. High-Le 

 Calcium Flocculi Slit set on Ha 

 Sun's Diameter = 0.28 meter. 



^ 





f 





■ ■«•■#-? . 



'5'. 





-:£\^-' 



wave lengt 

 I'abrN" said 



that 



for short portions of the spectrum plane gratings 

 may be even better than concave 



Mr. Adams gave 

 the report on the 

 determination of 

 Solar Rotation by 

 the displacement of 

 lines, and spoke of 

 the use of the plane 

 grating in measur- 

 ing Solar rotation 

 at Mount Wilson. 



Professor Frost 

 presented the re- 

 port of the Com- 

 mittee on the spec- 

 troheliograph. It 

 was decided that 

 daily photographs 

 of Calcium flocculi 

 should be con- 

 tinued. 



In addition to 

 the meetings, the 

 astronomers made 

 a detailed inspec- 

 tion of the instru- 

 ments used in the 

 advancement of 

 astrononi}', particular interest being taken in the new 

 tower telescope, 180-feet high including dome, and 

 • . - -..-, ^ ..;- its 80-foot deep pit for 



; the new combined spec- 

 -. ; trograph and spectro- 

 ' iieliograph. The tower 

 is surmounted by a dome 

 containing a coelostat 

 and necessar\' mirrors to 

 project the beam of light 

 on to the 12-inch object 

 glass, situated near the 

 summit of the tower, 

 which focusses the image 

 of the sun on the slit of 

 the spectrograph in the 

 linuse at the foot, the 

 -tiisitive parts of the 

 spectrograph being 

 situated in the under- 

 ground pit to maintain 

 constant temperature. 



The tower itself is 

 realK" two towers, one 

 within the other, having 

 al)out i-inches clearance 

 between them, so that 

 the inner one is shielded 

 b\- the outer from the 

 direct ra\'s of the Sun, 

 and also from the force 

 insulated portion which 

 (objective. 



-^ 

 "§??« 



4. Hsdro^cu (Ha) I'locculi photuj^raplu il 

 Snow Telescope and 5-ft. Spectroheliograph. 



of the 

 carries 



wind. It is 

 the coelostat 



this 

 and 



