﻿204 Mr. N. McCleland on the Absorption Spectra of 



The value of m is increased in ratio 1 : 1*6 if the atom? 

 are between two unsaturated carbons or if they are between 

 two phenyl groups. 



Using the above figures satisfactory results are obtained, 

 the difference between calculated and observed positions of 

 the bands being small except in very complex substances. 

 In these cases, however, the numbers and approximate 

 positions of the bands calculated and observed are in 

 agreement. 



In conclusion the author wishes to thank Prof. Sir J. J. 

 Thomson for his interest in this paper, and Mr. Gr. Birtwistle 

 for much valuable advice and criticism. 



August, 1914. 



References. 



1. Drude, Theory of Optics, Sect. II. ch. V. 



2. Russell & Lapraik, Trans. Chem. Soc. xxxix. p. 168 (1881). 



3. Brit. Assoc. Report on Dynamic Isomerism. 1911. 



4. Hartley. Phil. Trans. 1, clxx. p. 257 (1879). 



5. „ Phil. Trans. A, ccviii. p. 475 (1908). 



6. Stark, Steubing, Enklaar, & Lipp, Jahrb. jRadioalctiv. Electronic, 



x.p. 139(1913). 



7. Stark & Lew, ibid. p. 179. 



8. Hartley, Trans. Chem. Soc. xlvii. p. 685 (1885). 



9. „ " „ ,. „ liii. p. 641 (1888). 



10. Hartley, Debbie & Lauder. „ .. lxxxi. p. 929 (1902). 



11. Baly & Collie, „ „ '„ Ixxxvii. p. 1332 (1905). 



12. Balv & Ewbank. .. ., ., Ixxxvii. p. 1355 (1905 ). 



13. Stewart & Balv, „ „ „ lxxxix. p. 492 (1906). 



14. Baker & Balv/ ,. ., ., xci. p. 1122 (1907). 



15. Purvis, „ ., ., xcvii. p. 1546 (1910). 



16. „ „ ,. „ xcix. pp. 811, 1699 (1911). 



17. „ „ v ., xcix. p. 2318(3911). 



18. Purvis & McCleland, .. „ „ ci. p. 1514 (1912). 



19. „ ,. „ „ „ ci. p. 1810 (1912). 



20. „ „ „ .. „ ciii. p. 433 (1913). 



21. „ „ „ „ „ ciii. p. 1088 (1913). 



22. Purvis, „ ., .. ciii. p. 1630 (1913). 



23. Baly & Tuck, ,. ., ,. xciii. p. 1913 (1908). 



24. Ley & Engelhardt. Zeit. Pkys. Chem. lxxiv. p. 1 (1900). 



25. Hantzsch & Lipschitz, Ber. xlv. p. 3011 (1912). 



Appendix. — I am indebted for the following proof of the 

 existence of the mutual induction term to Mr. Birtwistle, 

 of Pembroke College. 



The field due to a system of electrons moving in small 

 closed orbits about mean points x^y x z^ x 2 y 2 z 2 , &c. has been 

 expressed (so far as the part affecting radiation is concerned) 



