33 We close these letters, Venerable Brethren, by manifesting anew the great hope We earnestly cherish that through this extraordinary gift of Jubilee granted by Us under the auspices of the Immaculate Virgin, large numbers of those who are unhappily separated from Jesus Christ may return to Him, and that love of virtue and fervor of devotion may flourish anew among the Christian people. Fifty years ago, when Pius IX, proclaimed as an article of faith the Immaculate Conception of the most Blessed Mother of Christ, it seemed, as we have already said, as if an incredible wealth of grace were poured out upon the earth; and with the increase of confidence in the Virgin Mother of God, the old religious spirit of the people was everywhere greatly augmented. Is it forbidden us to hope for still greater things for the future? True, we are passing through disastrous times, when we may well make our own the lamentation of the Prophet: "There is no truth and no mercy and no knowledge of God on the earth. Blasphemy and Iying and homicide and theft and adultery have inundated it" ( Os . iv.,1-2). Yet in the midst of this deluge of evil, the Virgin Most Clement rises before our eyes like a rainbow, as the arbiter of peace between God and man: "I will set my bow in the clouds and it shall be the sign of a covenant between me and between the earth" ( Gen . ix.,13). Let the storm rage and sky darken - not for that shall we be dismayed. "And the bow shall be in the clouds, and I shall see it and shall remember the everlasting covenant" ( Ibid .16). "And there shall no more be waters of a flood to destroy all flesh" ( Ibid .15.). Oh yes, if we trust as we should in Mary, now especially when we are about to celebrate, with more than usual fervor, her Immaculate Conception, we shall recognize in her that Virgin most powerful "who with virginal foot did crush the head of the serpent" (Off. Immac. Conc.).
Source: Ad Diem Illum Laetissimum (Vatican.va)