in the Invisible Prismatie Spectrum. <i? 
been possible to test these formule far from the visible spec- 
trum, wifence their constants have been in fact derived. This. 
desirable test we are now prepared to apply 
The simplest as well as the most widely used formula is that. 
of Cauchy, which as it is commonly written 
Ge 
(neat i+5) 
contains three unknown quantities, requiring for their deter- 
mination three simultaneous equations. Selecting the lines A, 
and H for this purpose, we have from the table just given 
the three equations, 
ear b é 
15 =a cian Diver hee eas tek caeues 
4=4+ OrG000)7 + (076000) 
e 
(0°58890)? * (0°58890)' 
13798 —@+4- 
0004+ saga < rsoeTay 
from which by elimination 
a=1°5593 b6=0°006775 e=0°0001137 
So that for this prism, the formula becomes, 
es tg ind mois wh 
— ause below this point the heat is absorbed by some! 
ent of our atmosphere 
i ever great the wave-length of the ray transm 
0 far below A as A is below D, is absolutely con 
riments, and all extra-polations ma Le 
have been deter~ — 
the visit 
® visible spectrum in which its constants 
ef 
