R. H. C. Davis's field notes containing observations and interpretations of architecture in Italy and France. His title from the front cover reads: "XVIII". The majority of the text is written in English with some cited quotes written in French and Latin. Each entry begins with a list of dates starting with when the structure was raised, when reconstructions or restorations were made, when battles took place which altered the architecture, when paintings were added, and when additions like towers were begun. The list is followed by summaries of architectural elements with illustrations. Some have a second chronology of the history of the surrounding city, typically quoted from another source. Within each entry, Davis makes theories about the origins of certain details, its sources of influences and inspiration. The theories are followed up by references to scholarly works in an attempt to prove or disprove the theory. Throughout the notebook are cross-references to entries in his other notebooks. Some entries have additions in a later hand such as when Davis revisited the site or discovered additional research at a later date.

The table of contents include: General bibliography, additional to [volumes] I-XVII; Meaux Cathedral (Marne) (S. Etienne); Abby Church of S. Germain des Pres; The Abbey Church of Saint Denis (Ile de France); the Pantheon; Crypt of Abbey of S. Paul, Jouarre (Seine-et-Marn); Priory of S. Martin-des-Champs (Cluniac); Senlis and the Cathedral of Notre-Dame, revisited; Emile Mala sur les Influences Arabes dans L'art Roman; L'art Pre-Roman by Jean Hubert (Paris: Nonuments d'Art et d'Histoire, 1938); Index.

The illustrations feature details of architectural elements such as towers, gateways, base molds, bay design, stone-work ornamentation, bases of columns, masonry, and capitals. Other illustrations are maps and floor plan layouts. Some illustrations are copied from research books and papers Davis read or studied. He borrowed heavily from Jean Hubert's book, L'Art Pre-Roman.