A plumb line is a line perpendicular to the horizon, hanging (through the air).
It will be just like 'Specs,' if it is a still night, to drop a plumb line and check himself.
One boy stands at Y and another at X, each with a plumb line.
The corpse no longer stirred; the chain was as motionless as a plumb line.
The mirror is always at hand, and a paper protractor on a piece of board, with a plumb line attached, serves as a quadrant.
A plumb line that is a little too long to reach the floor will, if swung so as just to touch the floor, describe a circle.
The Zenith is that point of the sky, overhead, toward which a plumb line points.
Your rocket leads shot up, and the plumb line dropped one hundred feet.
Supports of dressed stone truly fixed with the plumb line are perfectly stable of themselves.
Holding a plumb line at 350 miles per hour, she dropped upon the battle wagon below.