This manuscript of six pages is entitled "Diario de la expedición de reconocimiento hecha ... en los ... ríos del Sacramento y San Joaquin." It is the diary of exploration of the delta region by Fr. Narciso Duran and Lieutenant Luís Argüello. The two explorers started out together but later separated and still later reunited. Each kept an account, this one being that of Father Narciso. It should be studied in conjunction with that of Lieutenant Argüello. There are many points of disagreement which cannot be discussed in detail. It is to be noted that Father Fray Ramón Abella accompanied Father Duran on this expedition. Diary of the expedition of reconnaissance made to the rivers Sacramento and San Joaquin. _Viva Jesus._ Diary of the expedition of exploration made in the month of May of 1817 by the Commandant of the Royal Presidio of our Father San Francisco, Lieutenant Don Luís Argüello, with his launch San Rafael, alias "The Fine One," and by the Fathers Fray Ramón Abella, minister of the Mission of Our Father of San Francisco, and Fray Narciso Duran, minister of San José, with the launch named San José, alias "The Fisherman," in the only two rivers which enter the Port of Our Father San Francisco, called the Sacramento and the San Joaquin. _13th day of May._ We left the beach at the Presidio at ten o'clock in the morning of this day with a fresh wind, which lasted until we had crossed the entrance of the port. By rowing we arrived at twelve o'clock at the big island of Los Angeles [Angel Island], where we ate lunch. At five o'clock in the afternoon we left the island, and having passed Point San Pablo, which is on the side of the mainland of San José, we stopped at eight o'clock in the evening, having gone in the entire day six leagues toward the northeast. _14th day._ We set out at six o'clock in the morning, and with a light wind we arrived at noon at the end of the strait of the Chupcanes [i.e., Carquinez Strait]. The village of this name is Christian, part at San José, part at San Francisco. It is fourteen leagues distant from the latter and seventeen leagues north-northeast of the former. After lunch we set out with a fresh wind, which became strong by the middle of the afternoon, in the direction of the Ompines toward the east. In this area one recognizes the mouths of the only two rivers which flow through this strait to the Port: one comes from the north and northeast and is called the Sacramento, the other from the east and southeast and is called the San Joaquin. I say they are the only two rivers, for it seems that the many openings and branches which form so many islands of brush and tulares, as well also as some other rivers which are found here, all come to discharge their water into the two rivers mentioned. Thus although the western slopes of the Sierra Nevada form certain rivers, as has been stated, nevertheless all of them lose their identity and are lost in the two principal rivers just described.