304 ELC. Pickering on different forms of the Spectroscope. 
TABLE II.—60° Prisms. 
lsurface.| 1 prism. 2p. { 10 p. 
15 |18° 35')37° 10’| 74° 207 ue ‘a0l1ase 40" 186° '50’|371° 40° 
Deviation 1°6|23° 8'\46° 16’| 92° 32'/138° pe bee 4! |231° 20/1|462° 40! 
1-7 |/28° 13'156° 2671112° 52/1699 24’\225° 447 re 10’|564° 20/ 
15 | °756 1512 | 3°023 4.535 6-046 7-558 |15°116 
Dispersion 1°6| °833 1667 | 3°334 5-000 6°667 8°334 68 
CLT] -949 1899... S797 5°696 7594 9-493 |18°986 
15| 945 895 811 “jA2 686 “641 509 
Transmitted + 1°6| -920 853 “148 “672 618 “578 “491 
ey 
"888 ‘801 “681 “608 B65 ‘538 *505 
Taste IIl.—Angles of Prisms 67° 22’, 64° and 60° 56’. 
1°5 122° 38//45° 16’ fe 32’ 135" 48'\181° 4’ [226° 20’ 452° 40! 
Deviation 1°6 |26° 62° 156° 208° 260° 5 
17 129° 4’ |68° 8’ ae 16/|174° 24’|232° 32'|290° 40’ bie 20’ 
15 
Dispersion 16 1. 2 4 6 8 10 20 
17 
16 923 *863 "163 ‘691 "639 -600 520 
Transmitted 4 1°6| -899 “818 “702 "629 “582 “552 505 
Lt ‘874 “780 “657 *b88 *b49 *b23 -bO1 
Table I applies to ase of 45°. Table II to those of 60°, 
these being the forms in general use, and Table III. where the 
angle is such that the reflected light would be totally pola 
10 prisms of Deviation. Septic. Transmitted. Trans Xcos?- 
ey 305° 0’ 9°680 “e011 308 
60° 462° 40’ 16°668 "294 
64° ° 20°000 "268 
- Again, comparing cartes producing equal deviation, 
Devia Dispersion. Transmi Trans. X cos #- 
12 ier of 45° 366°." 11°616 "339 “268 
“ 
ag” 370° 8 13°334 532 *319 
64° 364° 14, 
