Revelation 15:1

"And I saw another sign in heaven, great and marvelous, seven angels having the seven last plagues, for in them is filled up the wrath of God."

Just as there were seven seals and seven trumpets which were symbols of judgment upon Jerusalem; so now there are seven vials that are symbols of judgment upon Rome.

They are called the seven last plagues; they were the last as regards Rome; the last warning she would get before her downfall. God gives men space to repent, he bears long and warns often for he is slow to anger and plenteous in mercy; but the last time comes at length.