constrain > afflict, distress (with implied restriction of liberty)
8 And oftentimes loud strokes, and ringing sounds
oftentimes > frequently
9 From under that deep rock most horribly rebound.
303.10
The cause some say is this: A litle while
2 Before that Merlin dyde, he did intend,
A brasen wall in compas to compile
4 About Cairmardin, and did it commend
Vnto these Sprights, to bring to perfect end.
6 During which worke the Ladie of the Lake,
Whom long he lou'd, for him in hast did send,
8 Who thereby forst his workemen to forsake,
Them bound till his returne, their labour not to slake.
1 The cause, some say, is this: a little while 2 Before Merlin died, he did intend 3 A brazen wall in compass to compile
in compass to compile > to build in a circle
4 About Caer-merdin, and did it commend
it > [the project] commend > entrust, commit