Question about the Application of Spredlight Lenses to N&W PL Signals

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Attached are two photos. 

The first photo shows the standard yellow Corning 5 3/8" lens furnished with the N&W PL-2 Position Light signals, with ribbed prisms cast into the glass. (And yes, you can see the "cat's eye" downward deflecting prism at the top, behind the signal lens.) (Photograph taken in my basement...) 

The second photo shows a green Corning lens as applied to the N&W Position Light signals in the early 1960s. Note the "checkerboard" pattern to the prisms. The back of the rim is marked "Spredlight Deflector or Horizontal Spread 25° Downward 15° Code 55225." 

My question is: Was it really necessary to change the pattern of the prisms on the lenses when adding color to the standard PL signals, or was this just a matter of a salesman generating some extra commissions? 

I also wonder how these 25° Spredlight lenses affected the range of a signal. 

As a matter of speculation on my part, the application of the "denser" colored red and green lenses (i.e. less "transmissibility" than yellow) might have been the occasion for the N&W jacking up its signal lamps from the older 9 volts 12 watts to the newer standard of 10 volt 18 watts. Denser lens? Just force more light through it ! 

The ostensible reason for the addition of color to the N&W Position Lights Signals was a side collision between northward passenger Train No. 2 and a southward freight train at the south end of Cloverdale Siding. 

As for the 25° of "spredlighting," perhaps someone thought this would be advantageous on some of the N&W's rather serpentine trackage. But who knows, since there don't seem to be any records??? 

-- abram burnett 

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