360 14 



sharp. For such images the intensitj' of the spectra of the II""* order, or d', will 

 be found comparatively high. 



In order to make the comparison between the spectra of the P' and II"'' orders 

 as direct as possible, d' = 'I mm was chosen to represent normal intensity of the 

 spectra of the II"'' order. For different values of d' the correction of the effective 

 wavelength to d' = '1 mm was found to be 



d' -08 



correction + 6'95 



number of images n . 74 



After smoothing the following corrections were adopted 



d' 



corr. . . . 



10 



•12 



•134 mm 







— 7-1 



— 10-9ju 



— 



43 



26 



•08 



•09 



•10 



•11 



•12 



•13 



•14 



•15 mm 



+ 7 



+ 3^ 







— 3- 



— 7 



— 10 



-13 



— 16/( 



These corrections are, as was to be anticipated, about twice as large as those 

 found for the distance between the two spectra of the P' order. 



The mean error of a single effective wavelength from the spectra of the II"'' 

 order was determined in the same way as above for the spectra of the P' order. 

 The values found are given in Table 8. 



Table 8. 



Spectra of II"'' order. 



equivalent diameter of central image, d' = -08 -09 '10 -11 -12 -13 -14 mm 



number of differences used 97 185 98 61 22 7 1 



square of mean error of distance between^ „ ^ „^„ ,„ „ 



^ ^^ . . TT H J r 271 184 210 141 132 119 312 u2 



the spectra of II"° order / 



I observed 38 56 49 73 78 86 33 m-2 



■weight of 7; ■ smoothed 32 44 56 68 80 92 104 m-2 



[ adopted 8 32 56 64 56 32 8 m-2 



The spectra of the II"'' order were measured on 703 images, the total weight 

 of the corresponding colour indices being 26412 m~^. 



9. Spectra of the IIT^ Order. 



For the spectra of the IIF*^ order a diameter d = ^25 mm of the central star- 

 image was chosen as representing normal intensity of the exposure. For other 

 values of d the adopted reductions to c? = •25 mm are contained in Table 9. In 

 the same table the square of the mean error of the effective wavelength for different 

 values of d is given followed by the smoothed weights, which have partly been 

 further reduced on account of the uncertaintj' of the corrections to normal intensity 

 of the image. 



