IS TUE VISCOSITY A DMVINITE PHYSICAL QUANTITY'? 59

Among gases air may be regarded as the standard substance
as water is among liquids. And if we compare the numerous
values for the viscosity of air obtained prior to 20 years ago, the
result is discouraging and has been often commented upon.
These values are given for 0° in Table XX.

TABLE XX.—VISCOSITY OF Am AT 0°C.

Method
<f>
<p
Observer

Transpiration .........
5,942

Graham (1846)

Oscillating disks .......

5,325
Maxwell (1866)

Oscillating disks ....... Oscillating disks.

5,814 5,590
Meyer and Springmuhl (1873) Puluj (1874)

Oscillating disks . .

5,556
Puluj (1874)

Transpiration
5,854

Obermayer (1875)

Oscillating disks. . . .

5,489
Puluj (1876)

Transpiration ........
5,951

Obermayer (1876)

Transpiration .........
5,650

E. Wiedemann (1876)

Transpiration
5 988

Obermayer (1876)

Transpiration .
5 952

Obermayer (1876)

Transpiration .....
5 848

0. Meyer (1877)

Transpiration ........
5,882

0. Meyer (1877)

Transpiration .........
5,747

0. Meyer (1877)

Oscillating disk ........

5,714
Puluj (1878)

Transpiration
5 650

Hoffman (1884)

Oscillating disk . . .

5,955
Schumann (1884)

Oscillating disk ... .

5,838
Schneebeli (1885)

Oscillating cylinder .

5,831
Tomlinson (1886)

Transpiration .........
5,770

Breitenbach (1899)

Oscillating cylinder ....

5,659
F. Reynolds (1904)

Transpiration
5 761

Tanzler (1906)

The transpiration method appears to give higher values for the
fluidity than are obtained by the other methods but the results
are not very consistent among themselves. However the follow-
ing table of recent values for the viscosity of air at 15° is very
satisfactory.
We have the authority of Fisher (1909) page 150, for the state-
ment that "No experimenter has made the attempt to apply
a correction to his measured pressures to allow for the kinetic
energy of the emerging gas." It appears probable that the exist-