To drawe a streight line from any pricke that is not in a
line, and to make it perpendicular to an other line.
Open your compas as so wide that it may extend somewhat farther,
then from the prick to the line, then sette the one foote of the
compas in the pricke, and with the other shall you draw a
compassed line, that shall crosse that other first line in .ij.
places. Now if you deuide that arch line into .ij. equall
partes, and from the middell pricke therof vnto the prick
without the line you drawe a streight line, it shalbe a plumbe
line to that firste lyne, accordyng to the conclusion.
[Illustration]
_Example._
C. is the appointed pricke, from whiche vnto the line A.B. I
must draw a perpendicular. Thefore I open the compas so wide, that
it may haue one foote in C, and thother to reach ouer the line,
and with y^t foote I draw an arch line as you see, betwene A.
and B, which arch line I deuide in the middell in the point D.
Then drawe I a line from C. to D, and it is perpendicular to the
line A.B, accordyng as my desire was.