A text book of physics, for the use of students of science and engineering (1918)
Duncan, John, d. 1941, Starling, Sydney George, 1873- · London Macmillan · leaf 642
a … Fig. 572.—Submarine periscope. Range-finders.--In order to measure the distance of an objectfrom the observer, the method of the staff and telescope may beemployed (p. 613), but this involves the placing of a standard oflength in the position occupied by the object. This is for manypurposes…
Physics
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