The nature of light is to throw out its rays. The nature of the Light of God is the same. If we study the rays minutely we shall see that from whatever angle we view them there is one central ray shooting forth with more intensity and with much more light than all the others. That means there is a central ray. Actually the emblem of the cross, which is most ancient, is derived from the study of light. The first glance shows the one central ray; the second glance develops that ray into a horizontal line, and the two lines then form a cross.