The Viscosity of Air

The viscosity of air has been remeasured with the rotating cylinder apparatus used by Day and Bleakney. All of the constants have been redetermined, and especial attention has been given to the corrections to the simple theory. The value obtained at 22°C is $\eta =1.8243\mathrm{}\pm 0.0045$ c.g.s. units. This raises the oil drop value of $e$ to 4.796 e.s.u. It is shown in the appendix that a correction must be applied for the opening between the suspended cylinder and the guard cylinders, and also a correction must be applied for the moment of inertia of the air carried around by the cylinder when determining its moment of inertia. Neglect of these corrections has introduced some additional uncertainty into other work.