27+ C. 8. Hastings—Ortieal Constants of Glass. 
values are relatively, though not absolutely, as accurate as the 
ers. 
The following table contains, in the columns under # 
’ 
increase of refractive index also in units of sixth place, corres- 
ponding to an increase of 1° C. in temperature. 
is ii FEE 
Line. i’ k Kk’ k ke K 
A 4°12 3°79 1:70 1°74 caf — "iT 
B 4°04 4°22 2°35 2°04 = <oe — 53 
C 3°96 4°45 277 2719 — 06 — ‘i 
D, 5°12 5°07 2°43 2°61 — 00 — '08 
5614 6°58 5°40 2°56 | 2°84 + “04 ee le 
E 54> 5°87 2°68 3°16 + 36 
F 5°69 6:57 3°52 3°63 — °09 + “14 
4548 7:24 4°32 4°09 +111 
G 8°53 7°85 3°86 4°51 +1°26 +144 
h 8°03 8°48 4°78 493 +1°05 +1°78 
3951 9°2] 8:99 6-04 5°28 + 3°22 + 2°06 
It is evident at a glance that the values of k’ increase in each 
case with the decrease of wave length; and it was found that 
the quantities could be embodied, within the limits of error of 
the observations, by a formula of the form 
1\2 
The significance of the constants a and # is clearly that the 
first is the change in refractive power for light of indefinitely 
great wave length, or briefly, the change in refractive gt 
z 
SE Aue Pew Rene eS fen 1°875-+-1°1105,. 
1 
i 8 eae k= 4424. “15555: 
i 
Ill nie --k=—1'813-+0°6045,. 
: f glass, computed in the 
ordinary way, are as 9:8:6 nearly, while the coefficients 10 
