The Size and Size Distribution of Fog Particles

Abstract

An apparatus for the microscopic measurement of fog particles is described. The particles were collected on a slightly greased glass slide and viewed with the aid of dark-field illumination. The particle sizes were measured either visually with an eyepiece micrometer or, more usually, by the subsequent measurement of photomicrographs. With the aid of this apparatus a series of fog particle size distribution curves were obtained. These curves are characterized by a single maximum which always occurs at a particle diameter which is an integral multiple of 3.1 microns. The curves approach the axis asymptotically for large particle diameters but have a definite minimum. An explanation for this minimum on the basis of certain properties of the nuclei of condensation is offered.