Is there a reference - magazine article, perhaps - describing an early
computer control system for a railroad switching yard?  It has not
turned up in my rough scratching about; hope one of you can spot it.
The thing was in use at a mid-continent yard, I think; can't remember
which.

In switching yards a yard engine would push a line of cars up a hump. 
From the top each car was released to coast singly down.  As it came
to a switch it would be diverted towards a track on which cars for a
specific designation cumulated. There they would be coupled into a
train and taken off to the destination yard.

This computer was digital but ferociously non-electronic.  A command
word consisted of eight balls, each either steel or glass.  The word
was assembled to designate the outgoing track on which the car in
question would end up. The balls of the word were allowed to fall
through parallel glass tubes.  Coils were wound around the tubes; a
set of coils corresponded to each of the sorting track switches in the
yard.  As the balls fell and passed through the coils, steel balls
generated electromagnetic pulses; glass balls did not.  So the
eight-bit command word triggered control signals to the track
switches.

This system, though you might be skeptical, really was in routing
service.  Can't remember how long, etc.

Given the racket it made it was labelled, of course, 'Hailstorm.'