Proof to No Purpose

You see this grntle stream that glides,
Shoved on, by quick-succeeding tides:
Try if this sober stream you can
Follow to th' wider ocean,
And see, if there it keeps unspent
In that congesting element.
Next, from that world of waters, then
By pores and caverns back again
Induct that inadultrate same
Stream to the spring from whence it came.
This with a wonder when ye do,
As easy, and else easier too:
Then ye may recollect the grains
Of my particular remains,
After a thousand lusters hurled,
By roughing winds, around the world.