Shielded Bottom Arms on N&W Semaphores ?

[NW Mailing List]

A number of the Valuation-era photographs of depots (stations) show an unusual arrangement of two-arm semaphore signals used on the N&W before the advent of the Automatic Block Signal System. These photographs probably date between 1916 and 1923. 


Description of Signals: For each direction, a Train Order office was provided with two lower quadrant semaphores, one over the other, on a common mast. The upper arm, with a square end, was the Manual Block Signal (horizontal = block occupied; vertical = block clear.) The lower arm, with a scalloped end, was the Train Order signal (horizontal = receive train orders; vertical = no train orders orders.) So far, this is a straightforward and easily understood arrangement. 


However, here are two mysteries attending these signals. 


(1) The bottom semaphore arms (the Train Order arms) were concealed from view in a tin cage when in the down ("no orders") position, so that they could not be seen from an approaching train. 


(2) The bottom arms (Train Order arms) had only one lens in the spectacle, namely a red lens. When the bottom arm was down ("no orders" position,) no green lens was provided and a metal blanking piece in the spectacle prevented the engineman from seeing the flame in the oil lamp. 


The net result is that the Train Order semaphore arm >> ONLY << gave an aspect (arm, light, or arm + light) when it was at red (receive orders.) If there were no Train Orders for delivery, the engineman would see neither a semaphore arm nor a light of any color. 


Not only was this an unusual arrangement, but it seems to violate several principles which later came to be accepted as common practice in the signal procedures of American railroads. 


So, here are my two questions: 


(1) Has anyone figured out the logic behind this arrangement, viz. concealment of the Train order arm when in clear position, and lack of a green lens upon its spectacle? What advantage did this arrangement procure? 


(2) When did this arrangement first appear on the N&W? 


-- abram burnett 

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