[D8724AAD], Letter from S F Armstrong to Thomas Alva Edison, July 12th, 1887


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[D8724AAD], Letter from S F Armstrong to Thomas Alva Edison, July 12th, 1887

Editor's Notes

Attachment to D8724AAC. On the letterhead of the Chicago, St. Paul & Kansas City Railway Company Engineering Department. "In reply to yous of the 7th inst. in reply to mine will sayd that my intention is to cause each train to signal in advance its presence and to leave such signal until it has passed at danger for instance suppose a train passing a curve sets into a signal at the opposite end of the curve at danger and also one at its present position these remain set until train arrives at the position of farther signal when as it passes the signal it sets the signal at saftey unless there is a following train on same curve which can counteract its [------] this could be used on straight line if necessary but do not conceive any necessity for same now to accomplish this I thought to use Electricity and the question came up can an induced current be made strong enough to work the signals if they are so built as to be in equilibrium at all times suppose the index consisted of an arm that when horizontal was danger but if perpendicular would leave a white light in the night or white larg[--] in arm on eather side of light a red glass inserted or even red cloth you would have a red light or danger signal now these the [-----] could be made to exactly balance each other so that a small force only would be necessary to move them from safety to danger or the reverse and the question with me was it possible to induce a current strong enough to set the signal as supposed. ## Now to illustrate suppose a train going in one direction comes to a curve it sets the signals at both ends and on a long curve intermediate signals of course a train on the same track would stop if going in the opposite direction and whistle giving an agreed signal for such cases or suppose it is another section following the engineer ought to know whether the train had had time to be over curve and if so should slow up bit if not he should continue on looking out for internediate signals and if these remain set should slow or if they are set at safety by advance train he should immediately set his current and again place signals at danger and so with each section of any train until all are passed each section when elaving setting the safety signal but any section when elaving setting the safety signal but any section on curve immediately setting danger signal, as soon as the engineer sees the safety signal; now as to the mechanism the arm could be made straight and balanced in center the rear enclosed to prevent sleet or snow falling on same the forward end being double and sufficient distance a part to permit a lantern being set between them as in this sektch (drawn diagram] by might or target by day the revolution on axel being accomplished by any machinery now if a current one way would set it the reverse current one way would set it the reverse current would replace signal to safety this could be done by the eingineer having a reversing mechanism on his engine to set the current in his wire in a contrary direction a special wire being placed around corner for this special purpose all being under the contraol of Engineer of train the reason for desiring an induced current is the ease with which the connection could be made with wire at any point." Marginalia by Ezra Torrance Gilliland: "present this so that [--] [----] get [--] [--] [---] [-----] Gill"




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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
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