Signalling.

In probably no branch of railway working has such striking progress been recorded in recent years as in the signal department. Although great changes have been witnessed in many directions in the signalling field, however, it is somewhat singular that until recently semaphore signals as developed in the infancy of railways continued to hold undisputed sway on all the Home lines. Now the semaphore signal of the old familiar type is to undergo a most important change, after serving for something like four score years.

In place of the lower quadrant semaphore, with an arm moving in the quarter of the circle below the horizontal to indicate “line clear,” there is now to be introduced the upper quadrant signal, i.e., with the arm raised above the horizontal to indicate “proceed.” This change is in accordance with the best modern practice as favoured on many European lines and in the United States, and the new form of semaphore is to become standard throughout all the Home railway systems.

The semaphore was first employed at New Cross, on the London and Brighton Railway, in 1841, and was the invention of Charles Hutton Gregory, the engineer of that line. The horizontal position of the arm represented “danger,” while to indicate “proceed” the arm was lowered and concealed in a slot in the post. With the adoption of block signalling Gregory's type of signal was still employed, but for the “clear” indication the arm was lowered not quite into the post, but sufficient to form a well-defined angle with it.