One conclusion which emerged from this imaginary operation was that all changes in electric and magnetic force (for instance, those caused by an oscillating circuit) sent waves spreading through space; and that these waves had the same transverse character, and the same speed, as light. 'We can scarcely avoid the inference', he wrote in a monumental sentence, 'that light consists in the transverse undulations of the same medium which is the cause of electric and magnetic phenomena.