Public Geological Lecture.

The last of the series of four public Friday afternoon lectures which are being given by the Geological department will be delivered in the Geological Lecture Room at 4.30 o'clock this afternoon by Professor J. E. Wolff. Professor Wolff's subject will be "Crystal Optics and the Structure of Crystals." The lecture will consist of two parts, the first showing the structure of crystals by means of the stereopticon and the second part illustrating by projections by the polariscope the relation which exists between crystal-structures and rays of light. In this last portion of the lecture the views used are highly colored and the result is a very beautiful effect on the sheet.