﻿78 Intelligence and Miscellaneous Articles. 



The dispersion therefore is 



N G — N e = 0-000014; N g — N c = 0*000115. 



3. Oxygen.— Mean index : 1-0002719. 



Nc=l'000255; N E = 3'000294; N G =1'000300. 



4. Hydrogen. — Mean index : 1*0001 .38. 



N c = l-000129; N E = 1*000140; N G =1'000153. 



5. Nitrogen.— -Mean index : 1*0003019. 



N c = 1-000258; N E = 1*000302; N G = 1*000321. 



6. Chlorine.— Mean index : 1*000774. 



N c = 1-000699; Ne= 1-000792 ; N G =1*000840. 



7. Cyanogen.— Meow index : 1-000S29*. 



N c = 1-000804; N E = 1*000834; N G = 1*000895. 



8. Sulphuretted Hydrogen. — Mean index: 1*000639. 



N c =l*OO0599; N E = 1-000647; N G =1*000691. 



9. Ammonia. — Mean index : 1*000390. 



N c =l*000374; N E = 1*000399; N G =1*000444. 



10. Carbonic Oxide. — Mean index : 1-000344. 

 N c =l-000301; N E = l-000350; N G =1*000391. 



11. defiant Gas.— Mean index: 1*000669. 

 N c =l-000652; N E = 1*000694; N G =1'000702. 



12. Marsh-gas. — Mean index : 1-000449. 



N c =1-000412; N E =1-000471 ; N G =1-000502. 

 Vapours. 

 Bisulphide of Carbon. — Mean index : 1*001592. 



N c = 1*001489; N E = 1*001609 ; N G = 1'001795. 

 The dispersion is 



N G -N c =0-000306; N G -N E = 0'000186. 



It will he remembered that M. Le Roux has recently found that 

 through the vapour of iodine the spectrum is reversed. I propose 

 to ascertain whether the dichroism noticed, by M. Le Roux is met 

 with in the vapour of bromine ; but this investigation presents diffi- 

 culties, and requires a knowledge of physical constants which have 

 not yet been determined. 



The subject of these researches, which tends to fill up a void in 

 science, was suggested to me in the laboratory of investigation in 

 the Sorbonne by Professor Jamin. I have been fortunate enough to 

 be a,ble to execute them in the physical laboratory of the Faculty of 

 Sciences at Dijon, and under the eyes of Professor Billet, who has 

 aided me by his advice, which is so valuable to all who are engaged 

 in optical researches. — Comptes Rendus, October 5, 1868. 



* We find for this gas an appreciable difference between Dulong's num- 

 ber and that which we have obtained. 



