To the Temple sacrifice is added the perpetual intercession of CHRIST, as the Great Angel of the Covenant (compare the prayer Supplices te rogamus), that is, Christ, presents His petition amidst the smoke which rises from off the altar of gold.The "mystery" Tractarian is Anglican Priest, Fr. John Mason Neale, well known for his translations of the ancient Latin hymns of the Latin liturgy into English, while retaining almost always the original Latin melody (if that's the right name for it).
Here is Neale's translation of the Sequence Coeli enarrant, written by Godescalcus in about AD 950, for the Feast of the Division of the Apostles which fell on July 15:
The Heavens declare the glory of the Son of God, the Incarnate Word, made Heavens from earth.
For this glory befitteth that LORD alone
Whose Name is the Angel of the Great Counsel.
This Counsel, the assistance of fallen man, is ancient, and profound, and true, made known to the Saints alone,
When this Angel, made Man of a woman, made an immortal out of a mortal; out of men, angels; out of earth, heaven.
This is the LORD GOD of Hosts, Whose angels sent into the earth are the Apostles.
To whom He exhibited Himself alive after His Resurrection by many arguments, announcing peace as the victor of death.
Peace be unto you, saith He; I am He; fear not; preach the word of CHRIST to every creature, before kings and princes.
As the FATHER hath sent Me, even so send I you into the world; be ye therefore prudent as serpents, be ye harmless as doves.
Hence Peter, Prince of Apostles, visited Rome; Paul, Greece, preaching grace everywhere; hence these twelve chiefs in the four quarters of the world, preached as Evangelists the Threefold and the One.
Andrew, either James, Philip, Bartholomew, Simon, Thaddeus, John, Thomas, and Matthew, twelve Judges, not divided from unity, but for unity, collected into one those that were divided through the earth:
Their sound is gone out into all lands.
And their words into the ends of the world.
How beautiful are the feet of them that proclaim good tidings, -- that preach peace;
That speak thus to them that are redeemed by the Blood of CHRIST: Sion, thy GOD shall reign;
Who made the worlds by the Word; Which Word was for us, in the end of the world, made Flesh:
This Word Which we preach, CHRIST crucified, Who liveth and reigneth, GOD in heaven.
These are the Heavens in which, O CHRIST, Thou inhabitest; in whose words Thou thunderest; in whose deeds Thou lightenest; in whose grace Thou sendest Thy dew:
To these Thou hast said: Drop down, O ye heavens, from above, and let the clouds rain the Just One; let the earth be opened and bud.
Raise up a Righteous Branch, Thou Who causest our earth to bring forth, sowing it with the seed of Apostolic words: through whose words grant, O LORD, that we, holding the Word of the FATHER, may bring forth fruit to Thee, O LORD, in patience.
These are the Heavens which Thou, Angel of the great Counsel, inhabitest, Whom Thou callest not servants, but friends; to whom Thou tellest all things that Thou hast heard from the FATHER.
By whose Division mayest Thou preserve Thy flock, collected and undivided, and in the bond of peace; that in Thee we may be one, as with the FATHER Thou art One.
Have mercy on us, Thou that dwellest in the heavens.