How soft this Prison is — Southdown Sheep

Southdown sheep need no bars due to their nature. It's their fate. Dungeon and home are the same due to kinsmanship, if one cannot find a new realm.

How soft this Prison is 1
How sweet these sullen bars
No Despot but the King of Down
Invented this repose

Of Fate if this is All 5
Has he no added Realm
A Dungeon but a Kinsman is
Incarceration-Home.
(F.1352/J.1334)
[1] Prison:: a grassland as sheep's prison.
[2] sweet, bars:: they like this prison (sweet home) without solid bars.
[3] Down:: a breed of sheep raised on the chalk downs of England (OED n.1 5), also called Southdown.
[3-4] King of Down, Invented:: a master who was not a despot but made the calm nature of the Southdown sheep.
[5] Fate:: the fate of sheep (or family members).
[6] added Realm:: other place than home.
[7, 8] Dungeon, Kinsman, Home:: dungeon and home are the same due to kinsmanship. Kinsman hints at Dickinson's father, who was not a despot.

Good Properties of Southdowns. "In Wiltshire, as in many other counties, the Southdown sheep are more frequently fed than any other. . . . They will lie quiet to feed, and stand folding and the winter well" ─ The American Farmer (1825)

The Southdown sheep are among the best for all hill countries where the grass is short; and their kindly properties have caused them to penetrate into almost all parts of the country. They have a patience of occasional short keep, and an endurance of hard stocking equal to any other sheep ─ The Penny Cyclopaedia (1842)