REPORT OF THE SECRETARY. 



79 



Table 2-a.— Solar constant values from pyrheliometry—Continwi]. 



Date. 



1904. 

 Janiiary 27... 

 February 11 _ 

 May 28 



Julys 



September 15 . 

 September 22 . 



October 4 



October 5 



October 21 .... 

 November Iti . 

 December 29 _ 



m\r,. 



January 20 



February".... 



March 2 



April 19 



April 22 



May 2 



May 8 _. 



May 20 



June 3 



June 22 



June 27 



Range of I 



air I Log. 

 masses. 



9^.0 

 7-2.9 

 1-1.9 

 2-1.7 

 4-2.0 

 4-3.0 

 7-3.2 

 5-2.7 

 (5-3.0 

 0-3.8 

 4-3.6 



9-3.4 

 8-3.4 

 6-2. 6 

 2-2.0 

 2-2.1 

 3-2.0 

 3-2.0 

 2-1.6 

 1-2.2 

 1-2.0 

 1-1.5 



.090 

 .113 

 .121 

 .158 

 .120 

 .099 

 .126 

 .145 

 .063 

 .095 



.067 

 .097 

 .088 

 .184 

 .112 

 .151 

 .111 

 .105 

 .128 

 .096 

 .140 



Radia- 

 tion com- 

 puted 

 from 

 pyrheli- 

 I ometrv. 



Grade of 

 pyrheliom- 

 etry obser- 

 vations. 



.813 

 .771 

 .757 

 .695 

 .759 

 .796 

 .748 

 .716 

 .865 

 .803 

 .855 



.857 

 .800 

 .816 

 .702 

 .773 

 .706 

 .774 

 .785 

 .745 

 .802 

 .724 



2.02 

 2.27 

 2.24 

 2.05 

 2.25 

 2.22 

 2.17 

 2.30 

 2.06 

 1.95 

 2.24 



2.07 

 2.12 

 2.23 

 2.17 

 2.21 

 2.18 

 2.09 

 2.14 

 2.22 

 2.17 

 2.28 



Excellent . . 

 Very good . 



Radia- I 

 tion com-! 



puttfd bylGrade of spec- 



spectro- tro-bolometric 



bolo- 1 observations. 



metric j 

 method. 



2.02 Fair. 



2.26 



Do. 



Poor. 



Excellent. 



Good. 



Passable. 



Good. 



Indifferent. 



(b) Transmission of the solar envelope. — As stated above tbe apparatus foi* 

 examining tbe solar image bas been provided with appropriate shelters, and 

 IS now jiiuch improved over its condition last year. The great coelostat was 

 exhibited at St. Louis in 3904, and as a substitute a smaller coelostat was 

 arranged at the Observatory shop. The larger coelostat was not returned from 

 St. Louis until January, 1905, and, in the press of preparation for the Mount 

 AVilson expedition, time could not well be spared to set it up, so that the smaller 

 instrument has served throughout the year. iNIany measurements, both of the 

 distribution of radiation along the diameter of the solar disk and of its distri- 

 bution in sun spots, have been made after the manner explained last year.o A 

 revision has been made of all the data obtained relating to the distribution along 

 a diameter, on the assumptions (1) that we study a phenomenon of absorption 

 only ; (2) occurring in a homogeneous medium situated outside the photosphere, 

 and (3) extending to 21 per cent of the solar radius. 



With these assumptions it appears that the form of the distribution curves as 

 shown in Plate VIII of last year's report agree within the experimental error 

 with that deduced from the ordinary simple exponential absorption formula. 

 As this formula in a logarithmic form is peculiarly tidapted to graphical illus- 

 trations and comparison of results, all the measurements have been reduced on 

 the above basis and the results to be given below in Table 3 depend on it. It 

 goes without saying that the assumptions made are not harmonious with our 

 conceptions of the sun's absorbing envelope, and they are only made for want 

 of better and for the sole purpose of more readily comparing the results of dif- 



a Smithsonian Report for 1904, p. 85. 



