Semidiameters [noun]

Definition of Semidiameters:

range, sweep

Each semicircular niche was about a foot in its semidiameter.

And with your compas take the quantitee of the semidiameter iustly.

For a right line either from the center unto the touch-point; or from the touch point unto the center is radius or semidiameter.

Then at the ende of eche semidiameter, I draw a touche line, whiche shall make righte angles with the semidiameter.

Whereby it dothe well appeare, that the side of anye sisangle made in a circle, is equalle to the semidiameter of the same circle.

As the semidiameter was only 28 inches, this large tree could have been but 168 years old.