782 
in which PR, is VeERpet’s constant, /, is the current in amp, @, is 
the corrected galvanometerdeflection for the wavelength 4358 A.U., 
and R;, J; and «; relate to the other mercurylines. As, owing to small 
leaks and to temperature fluctuations, the readings of the manometer 
did not remain perfectly stationary, the dispersion was calculated 
from 
hk, ad, ap (l48h) a, p, 
B, ae ae aps (1+ ôt) Tm B 
= 
hl 
in which d, is the density, p, the pressure and f, the temperature 
of the gas during the measurement with the line 4358, the subscript 
2 denotes the other wavelengths, 3 is the pressurecoefficient (taken 
from AMAGAT’s observations), and /; is equal to p; {1+ (t,—h)}. 
Since P, does not differ much from p,, deviations from BorLE's 
law need not be taken into account. For the reduction of the ob- 
servations at the lower pressure from 2805 to 2654 A.U. the rotation 
for the line 2805 was first taken to be unity, and the relative dis- 
2805 
persion was then obtained by multiplication by 
0 
The oxygen used was supplied by the “Oxygenium” Company, 
Schiedam. It was analysed in a Hempgr absorptionbulb filied with 
copper gauze, moistened with a solution of ammonia and ammonium 
carbonate. For the gas with which the most reliable results were 
obtained, 97 °/, of oxygen was found. 
The following table is from the photographs, obtained on the 21 
to the 25t of May: 
TABLE &@ 
iS pressure temp. _galv. deflect. 
Ain AU. “in atm. | in °C. mm. : 
4358 83.8 17.4 335.9 1.00 
4047 83.8 142 304.9 1.10 
3665 83.25 15 258.2 1.31 
3130 84.9 16.9 184.2 1.79 
2805 82.5 Luca 152.3 2.24 
2805 40.9 16.7 314.1 — 
2155 41.3 Ted 301.9 231 
2654 41.05 ig. |. 9260.4 2.50 
