No doubt all students of science have read more or less about Barus\u27 work on condensation phenomena as produced in a specially constructed fog chamber. As is known, his work has been done under the direction of the Carnegie Institution of Washington, founded particularly for the solution of research problems, involving much time and considerable expense. The prime purpose of his work, so far as I can interpret it, is to determine the part played by various kinds of nuclei in the atmospheric condensation of vapor. This, of course, is a very interesting problem to the student of physiography, as well as to the physicist