St. Leger, at twenty years of age, returned to Paris.  The celebrated Pingre was chief librarian of the Ste. GENEVIEVE COLLECTION; and St. Leger attached himself with ardour and affection to the society and instructions of his Principal.  He became joint SECOND LIBRARIAN in 1759; when Pingre, eminent for astronomy, departing for India to observe the transit of Venus over the sun’s disk, St. Leger was appointed to succeed him as CHIEF—­and kept the place till the year 1772.  These twelve years were always considered by St. Leger as the happiest and most profitable of his life.  During this period he lent a helping hand in abridging the Journal de Trevoux.  In September, 1764, Louis XV. laid the foundation-stone, with great pomp and ceremony, of the new church of Ste. Genevieve.  After the ceremony, he desired to see the library of the old establishment—­in which we have both been so long tarrying.  Mercier spread all the more ancient and curious books upon the table, to catch the eye of the monarch:  who, with sundry Lords of the bed-chamber, and his own librarian BIGNON, examined them with great attention, and received from Mercier certain information respecting their relative value, and rarity.  Every now and then Louis turned round, and said to Bignon, “Bignon, have I got that book in my library?” The royal librarian ... answered not a word—­but hiding himself behind CHOISEUL, the prime minister, seemed to avoid the sight of his master.  Mercier, however, had the courage and honesty to reply, “No, Sire, that book is not in your library.”  The king spent about an hour in examining the books, chatting with the librarian, (Mercier) and informing himself on those points in which he was ignorant.  It was during this conversation, that the noble spirit of Mercier was manifested.  The building of the library of St. Victor was in a very crazy state:  it was necessary to repair it, but the public treasury could not support that expense.  “I will tell your Majesty, (said Mercier) how this may be managed without costing you a single crown.  The headship of the Abbey of St. Victor is vacant:  name a new Abbot; upon condition, each year, of his ceding a portion of his revenue to the reparation of the Library.”  If the king had had one spark of generous feeling, he would have replied by naming Mercier to the abbey in question, and by enjoining the strict fulfilment of his own proposition.  But it was not so.  Yet the scheme was carried into effect, although others had the glory of it.  However, the king had not forgotten Mercier, nor the bibliographical lesson which he had received in the library of Ste. Genevieve.  One of these lessons consisted in having the distinctive marks pointed out of the famous Bible of Sixtus V. published in 1590.  A short time after, on returning from mass, along the great gallery of Versailles, Louis saw the head librarian of Ste. Genevieve among the spectators.. and turning to his prime minister,