NO. 5 



SOLAR VARIABILITY ABBOT, FOWLE, ALDRICH 



of the sun were taken. Then, in order to standardize the observations 

 (for it is to be remembered that the bolographic curves depend for 

 their ordinates on the sensitiveness of the galvonometer, the clearness 

 of the sky, and the sun's zenith distance, all of which vary from day 

 to day), the sums of the mean measurements at the center (given 

 half weight) and at 2/10, 4/10, 55/100, and 65/100 radius, were 

 taken. All the measurements were divided by this sum and thus 

 expressed in terms of a unit five times the mean height of the central 

 part of the U-shaped curve. 



" For illustration: On June 8, 1908, the following measurements 

 were made on a curve corresponding to wave length 0.501/x. Taking 

 the sum, 40.96, of the first five places (giving the central place half- 

 weight) and dividing this sum into the mean values at the several 

 places on the curve, we have the following values : 



Table (53) i. — Illustrative of reduction of drift curve observations 



Distances from center: cm. I 



Linear o.oo jo. 91 



Fractional 0.00 0.20 



2.50 

 o-SS 



9 80 



Heights: 



Advancing limb 



Following limb 



Mean '2x4.909.69 9.21 



Ratio, mean height to 40.961 .11961 .2366J .2249 

 Ratio to central height 1^.. i.oooo; .98621 .9379 



19.69 

 9.69 



9.16 

 9.26 



2-95 

 0.65 



3-41 

 0.75 



3.75 3-98 4-i8 J4 32 

 0.82S 0.87s 0.92 10.95 



4-70 



14.78 



8.74 18.41 7.61 6.96 6.35 ls.65 



8.81 ;8.36 7-68 7-03 6.37 'S-SS i^./u 



8-775 ,8.38s 7-645 ;6.99S 6.36 '5.615 '4-74 



2142J .2047 -18661 .1708 .1553 -13711 -1157 



■8932] -8536 .7781 .7123 -6476: .57171 .4825 



4.41 

 0.97 



60 



0947 

 3949 



^ The lowest line of the table is added in view of its interest, but is not used in the reduc" 

 tions. It is based on the standard central value .1199 found from 104 curves. It will be 

 further explained. 



" The following table contains the standard reduction values for 

 many wave lengths. It corresponds to the next to the last line of 

 table above, represents the mean of many days of observation, and is 

 used in preparation of the tables which follow it. 



AUXILIARY STANDARD REDUCTION VALUES 

 Table {54) 2. — Mean distribution of radiation along radius of solar disk 



1 On half the scale of other columns. 



