318 PROFESSOR L. BECKER ON THE DISTRIBUTION OF 



pictures VI6. and VII. the corresponding distances A 6 = 550, h 7 = 1000, and /* = 900, 

 k, = 1400; hence v equals -10 for & = 1000, and -17 for h = 1400, while the 

 accidental errors v are about 45 and 75, that is to say, four times as great as the 

 systematic errors. Compared with the actual residuals v left by the equations, 

 the systematic errors are still smaller. The result, then, is this : Let there be equal 

 blackness on the two adjoining halves of two neighbouring pictures (Nos. m and m+ 1) 

 of the corona at distances h m and h m+l , then h M and h m+l are also correlative distances 

 on the corona at which the ratio of the intensities equals F,,,_ ,, 1+1 . 



The result would have been different if the backgrounds of the two neighbouring 

 pictures had not been overlapping, i' = i+s would have been found instead oft, and 

 s could not have been separated from i. 



(g) The intensity of the diffused light of the sky can be disregarded on the first 

 five photographs. To prove this, I start from the equations [see (/)] 



(I m +S m ) a i m -fS a m1 < m:tl = constant for equal blackness. 



The lower sign belongs to the first half of the mth photograph, and the upper sign 

 to the second half. For the first five photographs s is small compared with i, hence 

 by (a), (b), and (c) 



" (i m + o- ra )% n = constant, where <r m = s (1 + F Mi m1 ) 

 * = F nm , where i' p = i p + a- p . 



* n 



<r m is the intensity which produces at aperture a m and exposure t m the same 

 blackness as the two superposed exposures to the diffused light. The distances 

 belonging to the intensities i' m and i' n are, by definition, correlative distances on the 

 corona. We obtain, then, in the same manner as explained in (f), 



fdh\ 

 art m = <r, ' 



and 



v = 



<r m is calculated by the above formula and s = 0'6, except for the first photograph 

 and the first half of the second. The values range between 0'8 and 2 '3. 



A minute before the beginning of totality the cap was removed from the object- 

 glass and during that time light must have been reflected into the camera by the 

 shutter, which was placed about an inch from the object-glass, and illuminated the 

 plate at the place where Photographs I. and lie*, were taken. The blackness of the 

 background lies between that of IV. and V., and I estimate tr, = 10 and cr 2 = 5. 



The calculated values of v do not amount to a third of the accidental errors v of 

 measurement (Table III.). It is, therefore, permissible to regard the corresponding 



