81 
ON AEGON AND ITS COMPANIONS. 
Argon. Repetition at 237'3°. 
p. 
V 
P.V. 
32-844 
959-1 
32460 
32-370 
899-3 
32370 
38-511 
827-7 
32267 
44-450 
777-6 
32233 
44-900 
715-8 
32142 
48-880 
654-7 
32001 
53-927 
595-3 
32103 
57-267 
560-0 
32069 
60-047 
534-0 
32067 
64-482 
499-7 
32222 
67-849 
474-1 
32170 
71-542 
450-1 
32203 
These results are graphically re})roduced on Plate 2. 
Determinatioji of Refractivity .—-The apparatus which we employed is essentially 
the same as that described by Lord Rayleigh, in the ‘ Proceedings,’ vol. 59, p. 202, 
and vol. 64, p. 67, and differed from it only in dimensions. The parallel tubes of the 
refractivity apparatus were of glass, and liad an internal diameter of 2 millims. ; their 
length was 32 ceidrins. ; the gauge-tubes were 4 millims. in diameter, and the con¬ 
necting tubes were of capillary bore ; and the total caj)acity at full pressure was 
5 cub. centims., but it was possiljle to work with 3 culi. centims. of gas. The focal 
leiiii'th of the lenses was 30 centims. 
The refractivity was determined in tlie manner previously desciPjed. 
Helium.0T238 
Neon.(I.) (0-235; IT.) 0^234 . 0-2345 
Argon.0-968 
Krypton.(1.) 1-450; (II.) 1-449 . 1-450 
Xenon . . (I.) 2-361 ; (II.) 2-365 ; (III.) 2-379 ; (IV.) 2-352 . 2-364 
The refractivity of helium and argon were })reviously determined (‘ Proc. Roy. 
Soc.,’ vol. 64, p. 190) ; that of neon was compared with hydrogen ; and the refrac¬ 
tivity of hydrogen compared with air was found equal to 0-4733 (‘Proc. Roy. 
Soc.,’ vol. 62, p. 227). 
Two samples of krypton were oljtained, one liy fractionating from argon (I.); 
VOL. CXCVII.- A. 
M 
