Some observations and considerations on making and function of the arch element showing Tyche of Salona

Sa？etak All Croatian authors who discussed the relief showing Tyche (Fig. 1) - the personification of Salona - have been of the opinion that this makes element of an arch, positioned to the left from its keystone, and that the keystone and the element to the right also contained other figural reliefs (M. Abrami？, N. Cambi, J. Jeli？i？-Radoni？). Some foreign researchers, however, deem this is the arch keystone, presenting different arguments for this (J. J. Wilkes, N. Gauthier). In this paper, the author is pointing out two important details that have not been taken into consideration in this discussion at all: the groove in the upper flat surface of the block (Fig. 2), and the iron ring at the bottom curved surface (Fig. 3). The facts that these two installations are situated in the same vertical axis, that the groove is by its make identical to the groove in the keystone from Aequum showing the bust of Roma (Fig. 5), and that the ring by its position and make is similar to those in the vault of the southern gate of the Diocletian palace (Fig. 6), strengthens the interpretation claiming this to be the keystone. This is supported also by several other details in its make: almost identical height of the side surfaces and their inclination, position of the flag with inscription in the siglas and formation of the cyma recta profile in the left side of the niche. The asymmetrical design of the element and the specific shape of the niche, previously taken as evidences of the stone being positioned in the left part of the arch, actually result from a change in the project made while the works were under way. The author came to this conclusion when testing and measuring it with a standard 0.5 m long spirit-level with a central and two lateral marks (bubbles). This showed that the flat surface at the right side of the element and the upper three profiles at the left side are at the same level, and by several centimetres higher than the two lower profiles. Between the two lower profiles and the niche remained a narrow vertical frame, also parallel with the right side. The figure of Tyche nowhere exceeds the height of the frame and the niche edge, i.e., its relief does not protrude forward, this clearly showing that the field in which it is situated has been created within the former flat surface. All these details are well noticed when it is watched from the left semi-profile (Fig. 4). The technological details of manufacturing are leading to the conclusion that the niche had initially been designed hexagonal - with a bottom horizontal side, two side perpendicular