This paper discusses the possibilities of using diagrammatic solutions for accurate astronomical navigation and gives a detailed description of two methods of doing so that have been put into effect in Germany. These methods, the ARG1 and the Astronomischer Rechenatlas, have previously been described in German publications and referred to in numerous reports and memoranda written in this country and the United States. So far as is known no authoritative description of these two aids to navigation has yet been published in English, and it is appropriate that this, the first, should have been written by Dr. Freiesleben, who played a prominent part in their development.—Ed.

The development of radio aids to navigation has not made astronomical navigation redundant, but it has given more force to earlier demands for the simplification of methods of reduction. No longer is it acceptable to have a large variety of alternative methods, and it is probable that attempts will be made to select a single method that is both simple and universally applicable.