Study of materials and technology of ancient floor mosaics' substrate

Ancient pavements are composed of a variety of preparatory or foundation layers constituting the substrate, and of a layer of tesserae, pebbles or marble slabs forming the surface of the floor. In other cases, the surface consists of a mortar layer beaten and polished. The term mosaic is associated with the presence of tesserae or pebbles, while the more general term pavement is used in all the cases. As past and modern excavations of ancient pavements demonstrated, all pavements do not necessarily display the stratigraphy of the substrate described in the ancient literary sources. In fact, the number and thickness of the preparatory layers, as well as the nature and the properties of their constituent materials, are often varying in pavements which are placed either in different sites or in different buildings within a same site or even in a same building. For such a reason, an investigation that takes account of the whole structure of the pavement is important when studying the archaeological context of the site where it is placed, when designing materials to be used for its maintenance and restoration, when documenting it and when presenting it to public. Five case studies represented by archaeological sites containing floor mosaics and other kind of pavements, dated to the Hellenistic and the Roman period, have been investigated by means of in situ and laboratory analyses. The results indicated that the characteristics of the studied pavements, namely the number and the thickness of the preparatory layers, and the properties of the mortars constituting them, vary according to the ancient use of the room where the pavements are placed and to the type of surface upon which they were built. The study contributed to the understanding of the function and the technology of the pavements’ substrate and to the characterization of its constituent materials. Furthermore, the research underlined the importance of the investigation of the whole structure of the pavement, included the foundation surface, in the interpretation of the archaeological context where it is located. A series of practical applications of the results of the research, in the designing of repair mortars for pavements, in the documentation of ancient pavements in the conservation practice, and in the presentation to public in situ and in museums of ancient pavements, have been suggested.

Nature in the books of seven metals – Ǧābirian corpus in dialogue with ancient Greek philosophy and Byzantine alchemy –

The Ǧābirian corpus was a receiver of ancient Greek ideas and, at the same time, a source of knowledge for the later Greek-speaking world, in particular for medieval Byzantine alchemy. Both aspects are explored in the dissertation with respect to the notion of nature. After a general introduction to the Corpus and the sciences described in it, particular attention is devoted to a Byzantine anonymous text, The Work of Four Elements, which was probably influenced by the Ǧābirian Books of Seventy. These texts exemplify how, in the theory of the Ǧābirian science, things are constructed from four natures (hot, cold, moist and dry), the balance of which defines what a thing is. By changing the balance of natures, one can transmute any metals into gold that is perfectly proportioned in terms of natures. Ǧābir presents the art of dyeing metals gold in the Books of Seven Metals which, along with chrysopoetic recipes, also include medical recipes and theoretical contents such as the theories of four humours, properties, and talismans. Moreover, Ǧābir postulated a substrate that does not change in itself and continues to exist when natures move in and out of things. Such primary existence is called the fifth nature as an additional principle to the four natures. This key concept for the Ǧābirian theory, which has been underexplored so far, is discussed through the textual and critical analysis of various unedited sources: the Books of Seven Metals and the Book of the Fifth Nature. This study confirms that the fifth nature was probably derived from ancient Greek philosophical concepts such as the Empedoclean particles, the Aristotelian fifth element and the Stoic pneuma. Thus, this research indicates the importance of the Ǧābirian corpus both in the history of alchemy and the history of philosophy.