Polybius, Histories

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Improvements In Signalling

This matter being agreed upon, the two parties must go to their respective points of observation; and each must have, to begin with, a stenoscope with two funnels, to enable him to distinguish through one the right, through the other the left position of the signaller opposite him. Near this stenoscope the tablets must be fixed, and both points, to the right and to the left, must be defended by a fence ten feet long and about the height of a man, in order to make it clear on which side the torches are raised, and to hide them entirely when they are lowered. These preparations completed on both sides, when a man wishes, for instance, to send the message "Some of our soldiers to the number of a hundred have deserted to the enemy,"—the first thing to do is to select words that may give the same information with the fewest letters, for instance, "A hundred Cretans have deserted," for thus the number of letters is diminished by more than a half and the same information is given. This sentence having been written on a tablet will be transmitted by five signals thus: The first letter is κ, this comes in the second group of letters and therefore on the second tablet; the signaller therefore must raise two torches on the left to show the recipient that he must look at the second tablet; then he will raise five on the right, because κ is the fifth letter in the group,¹ which the recipient must thereupon write on his tablet. Then the signaller must raise four torches on the left, for ρ is in that group, and two on the right, because it is the second in the fourth group, and the recipient will write ρ on his tablet: and so on for the other letters.