6 NINTH REPORT — 1839. 



My present Report will therefore be found to embrace only a 

 small number of media of the more important class, but in 

 which, after repeated examination, I think the results may be 

 relied on. 



Table I. 

 Indices determined by Fraunhofer. 



I.— Flint-glass, No. 13. Specific gravity, 3723. 

 Temp. 15°Reaum. = 18°'75 Centig. 



B. 



C. 



D. 



E. 



F. 



G. 



H. 



1-627749 



1-629681 



1-635036 



1-642024 



1-648260 



1-660285 



1-671062 



II. — Ditto, No. 23. Sp. gr. 3'724. Mean of observations 

 with two different refringent angles. 



1-626580 



1-628460 



1-6336665 



1-640519 



1-646768 



1-6588485 



1-669683 



III.-Ditto, No. 30. Sp. gr. 3*695. 



1-623570 



1-625477 



1-630585 



1-637356 



1-643466 



1-655406 



1-666072 



IV.— Ditto, No. 3. Sp.gr. 3-512. 



1-602042 



1-603800 



1-608494 



1-614532 



1-620042 



1-630772 



1-640373 



V. — Crown-glass. M. Sp. gr. 2*756. 



1-554774 



1-555933 



1-559075 



1-563150 



1-566741 



1-573535 



1-579470 



VI.— Ditto, No. 9. Sp.gr. 2*535. Temp. 14° R. = 17°*5 C. 



1-525832 



1-526849 



1-529587 



1-533005 



1-536052 



1-541657 



1-546566 



VII.— Ditto, No. 30. Sp. gr. 2*535. 



1-524312 



1-525299 



1-527982 



1-531372 



1-534337 1-539908 



1-544684 



VIII.— Oil of Turpentine. Sp. gr. 0*855. Temp. 8°*5 R. 

 = 10°*6 C. 



1-470496 



1-471530 



1-474434 



1-478353 



1-481736 



1-488198 



1-493874 



