Page:Popular Science Monthly Volume 22.djvu/169

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157
TIME-KEEPING IN LONDON.

shown in Fig. 1,[1] representing a back view of the clock-train. The crutch-axis, supported by the arm (c) and the back plate {b) of the clock-train, carries an arm (e), attached at f to the left-hand pallet arm. The pallets are carried by the crutch-rod (d). At gis attached a detent projecting toward the left and ending in a light curved

PSM V22 D169 Greenwich clock escapement.jpg
Fig. 1.—Greenwich Clock Escapement

spring. Near the top of the escape-wheel this detent carries a jeweled pin which locks the wheel. The action is as follows: When the pendulum swings toward the left, the arm (e) lifts the delicate spring at the end of the detent, the wheel is released and drops forward so that a tooth presses against the face of the pallet and gives an im-

  1. Figs. 1, 3, 4, 5, and 6, have been taken from Lockyer's "Stargazing," through the courtesy of Macmillan & Co., London, publishers, by permission of the author.