For semi-diameter and also for refraction and parallax, —9ʹ.
The difference between the semi-diameter of the base-ring at the breech of a gun, and that of the ring at the swell of the muzzle.
The semi-diameter of the earth's orbit is our standard measure for the universe.
Now this depth of 43,528 fathoms is only a seventy-fourth part of the semi-diameter of the earth.
The semi-diameter of the earth, is the distance from its surface, to its centre.
As Capella sees the semi-diameter of the terrestrial orbit only under an angle 22 times smaller, its distance is 22 times greater.
For the greatest length of a versorium has no moment or perceptible proportion to the earth's semi-diameter.