Budapest Régiségei 30. (1993)

TÁRGYI EMLÉKEK ÉS LELETEK = DENKMÄLER UND FUNDE - Noéh Ferenc: Fragment of a measuring instrument from Aquincum 293-295

Ferenc NOÉH FRAGMENT OF A MEASURING INSTRUMENT FROM AQUINCUM During the fall of 1990, Orsolya Madarassy, archaeologist at the Budapest Historical Museum recovered a unique find during the course of excavations at one of the sites being investigated in the 3rd district of Budapest. This site is located at lot No 17804, some 100 m from the amphitheater on Nagyszombat street; house No 94 on Lajos street had previously stood at this lot. The object itself is a 369 g fragment of a marble plate which is worked on both sides. The thickness of this plate varies between 13 and 15 mm. The outline of this fragment corresponds to an oblong shape 10 cm wide and 13.5 cm long. All four sides of the plate are bordered by fractures. These fractures are old, that is, the object was not broken during its recent recovery. This find is made from white marble with a cloudlike pattern of light grey graphite. This type of stone may be found in North Africa. If it is of European origin, it does not come from Italy but rather from Greece. Its volume is 136. 4 cubic cm, which means that the density of the material is 2.7 g/cubic cm. Neither the direction of the graphite stripes, nor the location of the incised design (to be discussed later) show the original dimensions of this object or the relation of its fragmented sides to the original, probably carefully worked edges. Drawings may be seen on both sides of this marble plate (Figs. A and B). Around the middle of the edge on side "A" the central point of concentric arches can be seen. At this point, a small depression seems to have been eroded into the marble suggesting that it frequently supported the pin-like axis of a compass or compass needle. Nine radii originate at this point, two of which (N

Q 5 and 8) also connect the inner circle (r = 61 mm) and the series of peripherally located circles (r = 85, 87 and 89 mm respectively). Of these two latter, a 2 degrees division was set between the two outermost circles. Ten degrees divisions occur between the middle and inner circles. Fragmentary Roman numerals may also be recognized outside the largest circle. The starting point of these divisions is located on the fragment itself at the radius marked 5 in this study. Radius 5 is perpendicular to radius 1. Radii 6, 7, 8 and radii 4, 3, 2 were drawn symmetrically to the left and right respectively. These three pairs of divisions form angles of 11°, 20° and 23,5° with radius 5. It is noteworthy that this latter value corresponds to an angle of special importance in astronomy: it is the angle between the celestial equator and plane of eclipses. Radius 9 is significantly less marked on this plate. It forms a 43,5° angle with radius 5, Radius 1 and the circle intersect right at the edge of this fragment, however, it may be assumed that this "radius" also continued beyond the circle. At the same time, it may be said with certainty that that radii 1 and 5 did not end in the centre of the circles but continued in a diametric fashion toward the opposite side of the circle. On side A of the fragment, the inner circle may be followed along its 146°. Two other segments of concentric circles also occur near the edge of this plate. They are, however, oriented differently and their center lay well below the present edge of the fragment the radii of these circles are significantly greater than those of the previously described circles. On the basis of the lengths and positions of chords, the radius of the larger circle must have measured approximately 97 mm. Nine symmetric circle segments may be seen on the B side of this plate. The centre of these circles does not fall within the fragment, but its estimated location can be reconstructed. According to these calculations the radius of the inner circle was 73 mm long and 106 mm in the case of the outer circle. The 73 mm measurement almost exactly corresponds to 4 digiti, that is, 1 palmus. The most complete four circle segments are represented by a central angle of almost 90°. These circles start at a common, radial line which is marked by a letter 'D' on one of its sides. Four of the nine circles origin on the fragment. In the case of the other five circles, only smaller segments of them occur on the marble plate. Four (abbreviated) city names are written next to the starting point of the four inner circles. From the inside out, these read as follows: SVENIS, ALEXA, RODO, ATHE. The missing letters were not erased or removed by accidental truncation. These words are the original, proper abbreviations of Alexandria, Rhodos and Athens. All of these four towns had an eminent place in scientific life during Antiquity. At that time, it was a well known fact that Syene was located at a renowned latitude: it was the border of summer solstice, as was known at that time. In his great, comprehensive work "Geógraphika" Strabo (64 B.C.? - A. D. 20?) wrote as follows: "the Tropics must be at Syéne, since at the time of the summer solstice the point of the sun dial has no shadow there". Syene, today known as Assuan, was made famous by the measurements of angles that were carried out by Eratosthenes (276 B. C? - 196 B. C.?). He took these measurements in Alexandria, an 293