458 P N P N On comparing the "available buoyancy" with the "greatest vossible load at 100 ft per foot superficial of roadway" for each of the bridge equipments in the preceding table, it will be seen that very few of the bridges are really capable of carrying the maximum load they may be called on to bear. Strictly speaking the roadway superficies should in all instances be proportioned to the buoyancy of the pontoon, or, as the central interval between the pontoons cannot be reduced below certain limits, the width of the roadway should be proportioned to the buoyancy ; in other words the " chesses " or planks which form the roadway should be made of a shorter length for a bridge which is designed for light traffic than for one which is designed for heavy traffic. The employment of chesses of different lengths for the pontoon equipment of an army would, however, be very inconvenient and troublesome, and this has led to the adoption of a constant breadth of roadway, on the under standing that the traffic will always be controlled by the officer in charge of the bridge. The latest form of pontoon for the English army is one with which the name of Colonel Blood, R. E., is mainly associated. Its powers are given in the lowest line of the preceding table. It is an open bateau with decked ends and sides partly decked where the rowlock blocks are fixed. It consists of six sets of framed ribs con nected by a deep kelson, two side streaks, and three bottom streaks. The sides and bottom are of thin yellow pine with canvas secured to both surfaces by india-rubber solution, and coated outside with marine glue. The central interval between the pontoons in forming a bridge is invariably maintained at 15 feet ; for the support of the roadway five baulks are ordinarily employed, but nine for the passage of siege artillery and the heaviest loads ; they fit on to saddles resting on central saddle beams. The pontoons are not immersed to within 1 foot of the tops of their "coamings" when carrying ordinary loads, as of infantry in marching order " in fours " crowded at a check, or the 16-pounder gun, which weighs 4800 lb ; nor are they immersed to within 6 inches when carrying extraor dinary loads, such as disorganized infantry, or the 64-pounder gun weighing 11,100 lt>. In designing this pontoon the chief points attended to were (1) improvement in power of support, (2) simpli fication in bridge construction, (3) reduction of weight in transport, and (4) adaptation for use singly as boats for ferrying purposes. One pontoon with the superstructure for a single bay constitutes a load for one waggon, with a total weight behind horses of about 4500 lb. For the British army in India the standard pontoon for many years was the Pasley ; it was seldom used, however, for boats could almost always be procured on the spot in sufficient numbers wherever a floating bridge had to be constructed. Of late years an equipment has been prepared for the Indian army of demi-pon toons, similar to the Blood pontoon cut in half, and therefore more mobile ; each has a bow and a square stern, and they are joined at the sterns when required to form a "pier" ; they are fitted with movable covers and can therefore be used in much rougher water than pontoons of the home pattern, and their power of support and breadth of roadway are the same, For the British army there is a light form of the Blanshard pontoon suitable for infantry un crowded, guns unlimbered, and cavalry in single file. The Berthon collapsible boat, for infantry in single file, is also employed ; when open it is 9 feet long and 4 feet wide; it weighs 109 lt> with a pair of oars and a removable thwart or seat (to enable it to be used as a boat), and can be slung on to a bamboo and carried by two men ; the superstructure for one bay weighs 97 lb, and is also carried by two men ; the width of roadway is 18 inches; twelve boats are required to bridge a stream 100 feet in width. The india-rubber pontoon does not appear to have been generally employed even in America, where it was invented. The engineer officers with the army of the Potomac, after full experience of the india-rubber pontoon and countless other inventions of American genius, adopted the French equipment, which they found "most excellent, useful, and reliable for all military purposes." The Russians in crossing the Danube in their war with Turkey in 1878 employed the Austrian equipment. Authorities. Colonel Lovell, R.E., Prof. Papers, Royal Engineers, vol. xii., 1S63 ; BriK.-Gen. Cullum, U.S.A. Engineers, System of Military liridges in use by the United States Army, 1863; Gen. Barnard, U.S.A., Report on Army of Potomac, ISfiS ; Lord Wolscley, Pocket-Dook fur Field Service, 1882 ; Military /fridges, Chatham, 1879. (J. T. W.) PONTOPPIDAN, ERIK (1698-1764), a learned Danish author, was born at Aarhuus on August 24, 1698, and studied divinity at the university of Copenhagen. On finishing his education he was appointed travelling tutor to several young noblemen in succession, and in 1735 he became one of the chaplains of the king. In 1738 he was made professor extraordinarius of theology at Copenhagen, and in 1747 bishop of Bergen, Norway, where he died on December 20, 1764. His principal works are Thcatrum Daniie reteris et modernx (4to, 1730), a description of the geography, natural history, antiquities, &c., of Denmark; Gcsta et Vestigia Danomm extra, Daniam (2 vols. 8vo, 1740), of which laborious work it is enough to remark that it was written before the rise of the modern historical school ; Annalcs Ecdcsiss, Danicse (4 vols. 4to) ; Marmora Danica Sdcctiora (2 vols. fol., 1739-41); Glossarium Norvegicum (1749); Del forstc Forsog paa Norges naturlige Historic (4to, 1752-54; Eng. trans., Natural History of Nonvay, 1755), contain ing curious accounts, often referred to, of the Kraaken, sea-serpent, and the like; Origcncs Ifafniciiscs (1760). His Danskc Atlas (7 vols. 4to) was mostly posthumous. POXTORMO, JACOPO DA (1494-1557), whose family name was CARUCCI, a painter of the Florentine school, was born at Pontormo in 1494, son of a painter of ordinary ability, was apprenticed to Leonardo da Vinci, and after wards took lessons from Pier di Cosimo. At the age of eighteen he became a journeyman to Andrea del Sarto, and was remarked as a young man of exceptional accomplish ment and promise. Later on, but still in early youth, he executed, in continuation of Andrea s labours, the Visita tion, in the cloister of the Servi in Florence- one of the principal surviving evidences of his powers. The most extensive series of works which he ever undertook was a set of frescos in the church of S. Lorenzo, Florence, from the Creation of Man to the Deluge, closing with the Last Judgment. By this time, towards 1546, he had fallen under the dangerous spell of Michelangelo s colossal genius and superhuman style ; and Pontormo, after working on at the frescos for eleven years, left them incomplete, and the object of general disappointment and disparagement. They were finished by his leading pupil Angelo Bronzino, but have long since vanished under whitewash. Among the best works of Pontormo are his portraits, which include the likenesses of various members of the Medici family; they are vigorous, animated, and highly finished. He was fond of new and odd experiments both in style of art and in method of painting. From Da Vinci he caught one of the marked physiognomic traits of his visages, smiles and dimples. At one time he took to direct imitation or reproduction of Albert Diirer, and executed a series of paintings founded on the Passion subjects of the German master, not only in composition, but even in such peculi arities as the treatment of draperies, &c. Italian critics, both contemporary and of later date, have naturally regarded this as a very perverse aberration. Pontormo died of dropsy on 2cl January 1557, mortified at the ill success of his frescos in S. Lorenzo ; he was buried below his work in the Servi. He was a man of solitary self- neglectful habits, a slow worker, receiving comparatively little aid from scholars, indifferent to gain or distin guished patronage, and haunted by an instinctive horror of death. PONTUS was the name given in ancient times to an extensive tract of country in the north-east of Asia Minor, bordering on Armenia and Colchis (see vol. xv. Plate II.). It was not, like most of the divisions of Asia, a national appellation, but a purely territorial one, derived from its proximity to the Euxine, often called simply Pontus by the Greeks. Originally it formed part of the extensive region of Cappadocia, which in early ages extended from the borders of Cilicia to the Euxine; but afterwards it came to be divided into two satrapies or governments, of which the northernmost came to be distinguished as " Cappadocia on the Pontus," and thence simply as "Pontus." The term is not, however, found either in Herodotus or Xenophon, though the latter traversed a considerable part of the region, and it is probable that it did not come into general use until after the time of Alexander the Great. Under the Persian empire the province continued to be governed by a satrap, nominally subject to the great king,
but apparently enjoying virtual independence, as no