Rays emitted by Glowing Platinum. 459 
Region 17 on Kirchhoff’s Seale 2445. 
Calc. Diff. Temp. (°) Observed, Calc. : 
0:009 +°001 1759°6 0-290 0°280 +7010 
1539°5 0-017 0-015 +002 1901°7 0-891 0891 “000 
1618°5 0°054 0-056 — 002 1932°; 1:320 1°321 —'001 
Temp. (°) Observed. 
0-010 
Region 18 on Kirchhoff’s Scale 2648. 
1653°6 0°067 0-050 +°017 | 1901°7 0-795 0-799 —"004 
1689°7 0112 0-080 +°032 | 1932°7 1-249 1°'249 000 
1689-7 0060 0°059 +001 | 19017 0750 0-750 000 
17596 0-207 0:202 +7005 ' 19327 1203 1200 +7003 
The size of the above differences bears witness to the difficul- 
ties which, aside from those which are unavoidable, even in the 
study of the most favorable colors at intensities best adapted to 
the eye, stand in the way of accurate results. t the lowest 
yellow and green ray The position of the ocular Nicol, 
at which each ray of the spectrum disappears, 1s given In the 
column mark °—a@” of The corresponding 
Taste VI 
Optical 
Region. (90—a)° sin” (—a) onion. Region. (9—a)° sin ? (90—a) action. 
7 ; 001719 01782 14 354 0°04620  0°0662 
8 1°45 0°00932 0°3284 15 50 007592  0°0432 
9 16 0°00363 0°6601 16 724 0°16! 070184 
10 1-0 0°00306 10000 17 830 021600 00142 
i es 0°01340 0°2281 18 9°36 027801 0-01117 
12 2-718 001611 0°1900 19 12°36 0°44662 0-0068 
13 2°42 002221 0°1380 20 15°36 0772320 070023 
visible spectrum. However valuable such researches might 
prove to show remarkable — of = eye = regard to 
its perceptive power for various colors, these very changes ren 
ihe catenins ts useless in the investigation of the real 
energy of the rays themselves. 
