Nearly all these instruments register the revolution of a small wheel of known circumference, which is run along the line to be measured.
The fort rises from a huge mass of granite rock, which with a circumference of nearly 2 m., juts up abruptly to a height of 450 ft.
The curves on railways are either simple, when they consist of a portion of the circumference of a single circle, or compound, when they are made up of portions of the circumference of two or more circles of different radius.
Knives are arranged around their circumference in such a way that the hopper feeding them presents an annular opening to the disk, say 7 ft.
In other machines a roll of narrow paper, in width equal to the circumference of the cigarette, is converted into a long tube, filled with tobacco, and automatically cut off into proper lengths.
The castle is a quadrangular structure of great strength, with rounded towers at three of the angles, and has a circumference of about 400 ft.