"You have your chronometer at hand?" I asked.
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"Certainly."
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"Well, take it into your hand. Pronounce my name, noting exactly the second at which you speak. I will reply as soon as I hear your words—and you will then note exactly the moment at which my reply reaches you."
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"Very good; and the mean time between my question and your answer will be the time occupied by my voice in reaching you."
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"That is exactly what I mean, Uncle," was my eager reply.
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