It looks as if some lines of this poem had been lost. The first
sentence has no subject unless 'That' in the second line be a
demonstrative--a very awkward construction.
If written by Donne this poem must have been composed about the same
time as _The Storme_ and _The Calme_. He is writing apparently from
the New World, from the Azores. But it is as impossible to recover the
circumstances in which the poem was written as to be sure who wrote
it.