Axial chromatic aberration of the human eye.

terminal of a direct current electric supply being connected to p, while the positive lead makes contact with the backs of those studs which it is desired to make luminous. The arrangement can be used for quite a number of purposes, and it is proposed to publish later the results of experiments in the reproduction of photographs, etc. For the present, in this preliminary paper, it is merely desired to point out that a new means is now available, by which, within a small compass, an almost unlimited number of separately con­ trollable luminous areas can be obtained ; that such areas, or points, can have their luminosity graded, by means of the applied voltage; that such luminosity can be established, or extinguished, at least some hundreds of times per second ; and that, since all the luminous points are automatically in parallel, being all connected to the negative pole (the electrolyte), only one contact is needed for each alloy unit.