1397 
ments were made for helium. According to Reyxoups the critical 
velocity would be 2960 °™/,..; in our experiments the greatest 
velocity was 105 °™/... All our observations are brought together 
in Table I. The notations are the same as in the previous paper 
about hydrogen. 
Again the first two experiments were used for the calibration 
of the apparatus, for which purpose we assumed as K. Sunmuer *) 
does, 4, .107 = 1887 and C in SUTHERLAND'’s formula = 78.2. In this 
way we got the values given under 74, .10’. These were corrected 
4 
for the change in = with the temperature and for the gliding. The 
y 
corrected values stand in column 7 under 4. 107. 
As can be seen, most of the measurements were made under a 
mean pressure of 40 cm. mercury. At 20°.1 K. we also took some 
measurements at 12 cm. mercury pressure. A glance at the table 
shows that the viscosity does not depend upon the density. 
Proceedings Royal Acad. Amsterdam. Vol. XV. 
TABLE: |: 
Viscosity of helium at about normal density, observations 
and results. 
es PomHg PemHg | Baden Pemtig Se ae 
204.50 | 10.83 | 36.81 | 13475 | 1.565 | — |) soo4 
294.55 7.892 44.43 | 13372 1.370 — 
250.3 9.870 42.98 | 9540.5 1.539 | 1806 1788 
20351 8.471 45.65 | 7828.5 1.622 | 1591 1564 
170.5 8.522 42.60 | 7191.2 1.851 | 1420 1392 
89.7 10.173 41.07 | 3201.0 2.709 943.7 917.9 
89.8 8.480 44.60 | 2933.4 2.241 945.6 919.2 
1505 9.744 42.57 | 1828.1 1.999 841.8 817.6 
74.7 7.037 45.30 | 3220.0 2.810 838.2 Sige2 
20:17 5.121 41.61 921.1 4.600 362.5 349.9 
20.15 5.566 39.49 | 881.0 4.516 364.6 352.0 
20.20 4.540 40.10 846.8 4.540 360.0 347.6 
20.16 4.528 11.15 | 1788.8 218 362.9 35155 
20.16 4.530 128 19672 2.018 362.0 307 
15.00 3.374 42.73 922.8 5.010 304. 1 293.1 
15.00 3.962 40.31 821.4 4.921 305.2 294.2 
15.00 1.270 41.55 | 1514.1 2.981 9015 296.4 
1) K. Scumirr: Ann. d. Phys. 30, 1909, p. 393. 
ay 
