Chauvet's journal "Ephemerides" was written in 1858-1882, but refers to Réunion and French matters as far back as 1657. The chronological arrangement of the journal is not a reliable indication of its contents because of lengthy reminiscences and historically informative correspondence, as Chauvet quotes some correspondence at length.

The entries after 1875 are sparse. The journal is intermittent, and records only certain things. His daily work and current events are referred to only briefly, but he writes with much detail about his observations of local natural history (especially botany and birds); the physical and mental development, illnesses, and death of his children, and the progress of his own grief; and news of (and the genealogy of) the Chauvet-Lafitte-Gilbert-Lambert-Hoarau families in Réunion, Nantes, and elsewhere. He keeps a log of each journey (at times in great detail, at times of daily positions only). He makes constant references to Réunion, comparing the local flora, and the seeds he grows in his trial gardens, to those he knew there; when there he measures and describes houses, writes down ghost stories, descriptions of all hurricanes since 1667, names and histories of the individuals his family held as enslaved persons, how to prepare vanilla beans and animal hides. He observes some astronomical phenomena (such as meteors) closely, and some storms (e.g, the New York blizzard of 1869). Some expenses are listed (e.g. the costs of the whole life of his daughter Ophelia, dead at 17 months). He is greatly interested in illnesses and yellow fever in New Orleans, remedies, and deathbed scenes.

Chauvet is a fair source for the daily life of New York and suburbs society, and a better one for Nantes--in both cases his correspondence (of which he records large portions) gives more details in his absence than the brief notes he makes when he is actually there. He records the political conversations of visitors from Latin America, Burma, and France. He makes brief reference to the effects of the US Civil War, and to draft riots, gives a detailed description of the troubles in Mexico, and becomes involved in the relations between the United States and Achin (now Aceh, Indonesia).

The journal is written in mixed French and English, and usually day by day, although there are some long gaps. It seems that it was made partly so that his son Albert would later learn something of Chauvet's background and life: his attitude toward his distant family is amiable and sentimental.