182 Dr. Tycho E:son Auren on 



Z. Element. I. II. III. IV. Mean. 



14 Si obs. 7-45 745 7*62 7*65 



corr. 7-18 7*09 7*08 677 7-03 



15 P obs. 7'81 8-07 8-37 8'64 



corr. 734 744 742 7'27 737 



16 S obs. 10-13 10-40 1055 10'36 



corr. 9 86 10-04 10-01 9-58 9'87 



17 CI obs. 12-84 13-19 13-17 13-96 



corr. 12-51 12-74 12-49 1298 12'68 



19 K obs. 18-9 19-0 200 19-4 



corr. 18-4 18'4 190 18"0 18-5 



20 Ca obs. 26-0 27-1 26'9 24-8 



corr. 25-7 26*7 26'4 240 25'7 



23 V obs. 44-1 45-1 47*2 46-5 



corr. 436 . 44-5 462 45'1 44*9 



24 Cr 50-4 53*6 53*5 52'1 52'4 



25 Mn 60-1 61-1 62'5 597 60-9 



26 Fe 69-2 69'4 70-5 68-2 69'3 



27 Co 83-4 82-9 85-9 80'2 83-1 



28 Ni 88-6 93*5 950 93-0 92-5 



29 Cu 100 100 100 100 100 



30 Zn 112 114 116 113 114 



33 As 159 168 171 166 166 



34 Se 181 183 190 191 186 



35 Br 193 203 208 206 203 



37 Eb 259 269 266 265 265 



38 Sr (263) 274 289 292 285 



42 Mo (338) 353 380 382 371 



45 Rh (393) 432 462 440 445 



46 Pd (422) (473) 500 486 493 



47 Ag (414) (475) 544 510 527 



50 Sn 420 536 646 717 — 



53 I 413 519 618 756 — 



56 Ba 431 527 672 878 



82 Pb 855 898 945 950 — 



It appears from the table that K ,q for the lightest 



elements increases with a decreasing wave-length, but 

 starting from Mg this progress lessens more and more when 



the atomic number increases. As for the elements Sn, 

 I, and Ba, selective absorption plays a considerable part : 



that is why the values found for these elements are not 



comparable with the other values. At Pb, «p b / Cll increases 

 markedly as the wave-length is diminishing. By means 



