PETRONIA, AMNIS
a brook that had its source in a spring, the Cati fons, on
the west slope of the Quirinal, and flowed across the campus Martius into
the Tiber (Fest. 250:
Petronia amnis est in Tiberim perfluens, quam
magistratus auspicato transeunt, cum in Campo quid agere volunt, quod
genus auspici peremne vocatur; cf. 45:
Cati fons ex quo aqua Petronia
in Tiberim fluit dictus quod in agro fuerit Cati). The
CATI FONS (q.v.)
is now usually identified with a spring in the cortile di S. Felice of the
royal palace in the Via della Panetteria (cf. acqua di S. Felice, LA 236),
close to the ancient porta Salutaris. The Petronia stream probably
followed the line of the present underground channel which runs south-
west across the Piazza Venezia, and westward to the east end of the
porticus Pompeiana. From this point its course is doubtful. Whether
after uniting with the
AQUA SALLUSTIANA (q.v.) it turned south and
flowed into the river opposite the island (HJ 473; KH i, ii), or continued
west under the porticus Pompeiana, and flowed into the Tiber near
the navalia (
AR 1909, 67-76), is as yet undetermined. The importance
of this stream lay in the fact that it was the boundary of the city auspices,
and necessitated the taking of the auspicia peremnia whenever the
magistrates crossed it to preside over the comitia centuriata (Mommsen,
Staatsrecht i. 97, 103; Jord. i. I. 139, 267; University of California
Publications in Classical
Philology ii. 272-273).
