FOGGIA, a town and episcopal see of Apulia, Italy, capital of the province of Foggia, 243 ft. above sea level, in the centre of the great Apulian plain 205 m. by rail S.E. of Ancona and 123 m. N.E. by E. of Naples. The pop. of the commune in 1931 was S 7,232. The name is perhaps derived from the pits or cellars under the pavement slabs of the open spaces (foveae) in which the grain of the neighbourhood is stored. The town is the mediaeval suc cessor of the ancient Arpi, 3 m. to the N. ; the Normans, after conquering the district from the Eastern empire, gave it its first importance. The date of the erection of the cathedral is 1172; it retains some fine Norman architecture but was much altered after the earthquake of 1731. Only one single gateway of the palace of the emperor Frederick II. (1223, by Bartolommeo da Foggia) is preserved. Here died his third wife, Isabella, daughter of King John of England. Charles,of Anjou died here in 1285. After his son's death, it was a prey to internal dissensions and finally came under Alfonso I. of Aragon, who converted the pastures of the Apulian plain into a royal domain in 1445, and made Foggia the place at which the tax on the sheep was to be paid and the wool to be sold. It is still a great wool market, and the centre of an associ ation (the Ovile Nazionale) for improving the breed of sheep. Foggia is a railway centre, on the main line from Bologna to Brindisi, where this is joined by the line from Benevento and Caserta. There are also branches to Rocchetta S. Antonio (and thence to either Avellino, Potenza, or Gioia del Colle), to Man fredonia and to Lucera.
See R. Caggese, Foggia e la Capitanata (Bergamo, Arti Grafiche, 1910) well illustrated; A. Haseloff, Bauten der Hohenstaufen in Unteritalien, i. (Leipzig, 1914), 67 sqq.
are employed for the purpose of guidance or warning when visual marks or signals are obscured by fog or their visibility is materially reduced by atmospheric conditions. Permanent fog-signals intended for the guidance of the mariner are usually established in conjunction with coast and harbour lighthouses and lightships. For warning signals made during fog by vessels under weigh or at anchor see NAVIGATION. Fog-signals are used in railway working to warn engine drivers when the ordi nary signals are obscured by fog; these commonly consist of detonators, fixed on the rail, which are exploded as the leading wheel of the engine passes over them (see RAILWAY SIGNALLING).
Coast fog-signals are of three kinds: (a) Aerial-acoustic; (b) Submarine-acoustic, including submarine bells and oscillators, which are usually established on light-vessels as an auxiliary to an aerial-acoustic signal; and (c) Wireless or Radio-fog-signals. Aerial-acoustic signals may be divided into three classes; first, those sounded by compressed air, such as sirens, diaphones and reed-horns; secondly, explosive signals, including nitrated-gun cotton charges, guns and rockets, the two last now seldom used; and thirdly, bells and gongs. The use of wireless-fog-signals has been largely extended since 1921, when the first permanent coast signal of this description was established, and they are of great importance to aerial as well as to marine navigation. Aerial acoustic signals are audible at greatly varying distances and, under certain atmospheric conditions, may be heard at a considerable distance though at the same time wholly inaudible in intervening areas. Wireless and submarine signals, on the other hand, are unaffected by the atmospheric conditions which impair the audi bility of aerial sound-signals. (See LIGHTHOUSES.) (N. G. G.)