Page:Passages from the Life of a Philosopher.djvu/471

Rh If the opaque cylinder which intercepts the light consists of two cylinders, A and B, connected together by rods: thus—

Such occultations are very distinct, and are specially applicable to lighthouses.



In the year 1851, during the Great Exhibition, the light I have described was exhibited from an upper window of my house in Dorset Street during many weeks. It had not passed unnoticed by foreignes, who frequently reminded me that they had passed my door when I was asleep by writing upon their card the number exhibited by the occulting light and dropping it into my letter-box.

About five or six weeks after its first appearance I received a letter from a friend of mine in the United States, expressing great interest about it, and inquiring whether its construction was a secret. My answer was, that I made no