coverer. Sebastian Cabot, however, having taken on its banks a considerable booty from the Indians, gave it its present name. Estimated by the body of water which it pours into the ocean, it is one of the largest rivers in the world. It is, however, properly speaking, but a continuation of the PARAGUAY and PARANA, which see. See also AMERICA, SOUTH. When the Parana takes its more decisive bend to the south-east to join the Uruguay, and the two streams expand together, they become properly the La Plata, and through this channel the great body of water formed by the confluence of the Parana, the Paraguay, and the Uruguay, flows into the ocean and forms an estuary of fresh water without parallel for width and magnificence. It is 150 miles broad at its mouth, from Cape St. Maria to Cape St. Anthony but some geographers have considered the point of Monte Video on one side, and the Punta de Piedras or Stony Point on the other, as its proper boundaries. Between those promontories it is about eighty miles broad. The water, however, neither loses its freshness, nor feels the influence of the tide in any considerable degree, between the first mentioned extremities. At Buenos Ayres, about 200 miles from the mouth, it is about thirty miles broad; and, the shores being little elevated, the eye can seldom reach from one side to the other. This noble expanse is, notwithstanding its extent, deformed by rocks and sand-banks, and rendered of dangerous navigation by shoals and shallows. Impetuous torrents of wind also sweep, at intervals, over the vast plains of the Pampas, to the south-west of Buenos Ayres, and rush down this wide opening with amazing fury. It has been observed, however, that a thunder-storm generally precedes the ravages of the Pamperos, and gives sufficient notice to mariners to prepare for them. The only port in this quarter which is adapted for the safety of ships of considerable burden is that of Monte Video; though those of Maldonado, Barragon, Buenos Ayres, and Colonia, afford anchorage. The La Plata was formerly it is said navigable as high as the city of Assumption for large ships; but from the accumulations of sand this is certainly now impracticable. There are two great banks, which are the terror of mariners; i. e. the English and the Ortiz bank. The former is the most advanced toward the ocean, and is of considerable extent. Occasionally, and when the floods come down the rivers, it is covered for several fathoms, but has in general only a few feet water: the same may be said of the Ortiz bank, which lies higher up, and more across the river, being of greater length but less breadth. Still further to perplex the navigation here is a reef of rocks and shoals stretching out from Purita de Piedras, and rendering the entrance along the southern shores of the river of great intricacy and danger. The northern channel is at once narrower and deeper than the southern. Ships generally make Cape St. Maria; and their best way is to range along the northern shore, till they are clear of the Ortiz, between which and Fisher's bank, off Colonia or St. Sacrament, there is a good passage to VOL. XVII. the road of Buenos Ayres. In the lower part of the river there are very few islands. That of de Lobos, or the Wolves (so called from the seals and other amphibious animals that frequent it), lies off the Punta de Este, surrounded by dangerous rocks. The Isle de Flores, or of Flowers, lies between the English bank and the port of Monte Video, and affords tolerable anchorage. San Gabriel protects the roadstead of St. Sacrament, until near the confluence of the Uruguay and the Parana; where on one side is the island of Martin Garcia, and on the other that of Palmas. The difficulties of this navigation have been found to be much exaggerated by the policy of the Spaniards. The soundings decrease regularly from fifteen to four and three fathoms water, and the bottom varies from sand at the mouth, to rocky clay, thick mud, and sediment. PLATEA, or PLATEA, an ancient and strong town of Boeotia, at the foot of Mount Citheron, on the borders of Megaris and Attica, between Mount Citharon and Thebes; famous for a battle fought between Mardonius, the Persian general, and the united Spartans and Athenians, under Pausanias and Aristides, wherein the former were defeated with great slaughter. The Persian army consisted of 300,000 men, of whom scarcely 3000 escaped. The Grecian army lost only ninety-one Spartans, fifty-two Athenians, and sixteen Tegeans. The plunder of the Persian camp was immense. This decisive victory, which from that period secured the liberties of Greece against the power of the Persians, was fought on the 22nd of September, A. A. C. 479, the same day on which the Greeks obtained another important victory at Mycale. See MYCALE. The Greeks, in memory of it, built a temple to Jupiter Eleutherius, and instituted the games called Eleutheria. Plataea was taken by the Thebans, after a famous siege in the beginning of the Peloponnesian war; and afterwards destroyed by the Spartans A. A. C. 427. It was rebuilt by Alexander the Great; but is now in ruins. These may, however, be traced in all their extent. Their form is triangular, the circuit about 3200 yards, or a mile and three quarters. At the south angle evidently stood the citadel; the whole remaining masonry consists of blocks accurately hewn and well put together. PLATEANS, the people of Platea. They were greatly attached to the Athenians, and sent them 1000 men, when Greece was invaded by Datis the general of Darius. PLATALEA, the spoonbill, in ornithology, a genus belonging to the order of grallæ. The beak is plain, and dilates towards the point into an orbicular form; the feet have three toes, and are half palmated. The species are distinguished by their color. 1. P. ajaja, the roseate spoonbill, is but a little less than the white. The bill is marked all round with a furrow parallel to the edge, and is of a grayish white color, so transparent as to show the ramification of the blood-vessels belonging to it; the forehead is of a whitish color between the bill and eyes and throat; the plumage is a fine rose color, deepest on the wings; the legs are gray, the claws blackish, and the 2 H toes have membranes as in the next species. The variety of this species is entirely of a beautiful red color, having a collar of black at the lower part of the neck; the irides are red. Latham imagines it is the roseate in full plumage. It is said to be of a blackish chestnut the first year; becomes rose-colored the second; and of a deep scarlet the third. It lives on small fish. 2. P. leucorodia, the white spoonbill, is about the size of a heron, but somewhat shorter in the neck and legs. The bill is more than half a foot long, and, like that of the rest of the genus, is shaped like a spoon; the color of the bill is very various, being in some birds black; in others brown, and sometimes spotted; from the base to two-thirds of its length several indentations cross it, the rising parts of which are of a dark color; the tongue is short and heart-shaped, the irides are gray, the skin of the lore round the eyes and of the throat is bare and black, the plumage is entirely white, though in some specimens the quills were tipped with black; the legs are generally either black or of a grayish brown color; between the toes there is a membrane connected to the outer one as far as the second, and to the inner as far as the first joint. This bird,' says Latham, is found in various parts of the old continent, and from the Ferro Isles near Iceland to the Cape of Good Hope. It frequents the neighbourhood of the sea, and has been met with on the coasts of France and at Sevenhuys, near Leyden, in great plenty, annually breeding in a wood there. The nest is placed on high trees, near the sea-side. The female lays three or four white eggs, powdered with a few pale red spots, and of the size of those of a hen. They are very noisy during breeding time, like our rooks; are seldom found high up the rivers, chiefly frequenting the mouths of them. Their food is fish, which they often take from other birds, in the manner of the bald eagle; also mussels and other shell fish, being found in greatest numbers where these are plentiful; and they will also devour frogs and snakes, and even grass and weeds which grow in the water, as well as the roots of reeds. They are migratory, retiring to the warmer parts as the winter approaches, and are rarely seen in England. Their flesh is said to have the flavor of a goose, and is eaten by some, and the young birds have been thought good food. The two varieties of this species are equal in size to the roseate species. The bill of the first is reddish; the plumage mostly white; the feathers of the wings partly white and partly black, and the legs reddish. The plumage of the other is entirely white, not excepting even the quills. It has a crest of feathers whose webs are very loose, and separated from one another; the bill is of a rufous gray color, having red edges, and the legs are of a dull pale red. They both inhabit the Philippine Islands. 3. P. pigmea, the dwarf spoonbill, is about the size of a sparrow. The bill is black, longer than the head, flat at the end, and nearly of a rhomboidal form; the angles and top of the upper mandible are white, the tongue is smooth, the body is brown above and white beneath, the quills have white shafts, the tail is rounded, . short, and of a brownish white color; the feet have four toes, are cloven, and the claws are pointed. It inhabits Surinam and Guiana. PLATANE, n. s. Fr. platane; Lat. platanus. The plane tree. The platane round, Milton. The carver holm, the maple seldom inward sound. Spenser. I espied thee fair and tall, Under a platane. PLATANUS, the plane-tree, a genus of the polyandria order and monœcia class of plants, natural order fiftieth, amentaceæ. There are two species 1. P. occidentalis, occidental or western planetree, rises with a straight smooth stem to a great height, branching widely round. It has lobated leaves seven or eight inches long, and from nine or ten to twelve or fourteen broad, divided into three large lobes, with very small flowers, collected into round heads, succeeded by round rough balls of seeds. It is a native of Virginia and other parts of North America, where it attains an enormous size, and is remarkable for having its stem of an equal girth for a considerable length; some trees being eight or nine yards in circumference. 2. P. orientalis, oriental or eastern plane tree, rises with a very straight smooth branching stem to a great height. It has palmated leaves six or eight inches long and as broad, divided into five large segments, having the side ones cut into two smaller, green above, and pale underneath; and long pendulous pedunculi, each sustaining several round heads of close-sitting, very small flowers; succeeded by numerous downy seeds, collected into round, rough, hard balls. It is a native of Asia and many parts of the east, and grows in great plenty in the Levant. The varieties of these two species are the Spanish or middle plane tree, having remarkably large leaves of three or five narrower segments; and the maple-leaved plane tree, having smaller leaves, somewhat lobated into five segments, resembling the maple tree leaf. All these elegant trees are of a hardy temperature, so as to prosper here in any common soil and exposure in our open plantations, &c., and are some of the most desirable trees of the deciduous tribe. They were in singular esteem among the ancients of the east for their extraordinary beauty and the delightful shade they afforded by their noble foliage. The leaves commonly expand in May, and fall off early in autumn; and the flowers appear in spring, a little before the leaves, being succeeded by seeds, which in fine seasons frequently ripen here in September. These fine trees are singularly fitted for all ornamental plantations. Their straight growth, regular branching heads, and the lofty stature they attain, together with the extraordinary breadth of their luxuriant leaves, render them extremely desirable furniture to adorn avenues, lawns, parks, and woods; some disposed in ranges, some as single standards, others in clumps, some in groves, &c. The propagation of these trees is by seed, layers, and cuttings. The seeds frequently ripen in these parts, and are also procured from other countries, and may be obtained of the nurserymen or seedsmen. The best season for sowing them is autumn, if they can be then procured. Choose a somewhat shady moist soil; and having dug the ground, and raked it fine, form it into four feet wide beds, and either scatter the seeds evenly on the surface, and rake them in, or previously with the back of a rake turn the earth off the surface nearly half an inch deep into the alleys; then sow the seed, and directly, with the rake turned the proper way, draw the earth evenly over the seeds, and trim the surface smooth; many of the plants will rise in spring, and some probably till the spring following. When they are one or two years old plant them out in nursery rows, two or three feet asunder, and about half that distance in the lines; to remain till of a proper size for final transplantation. The method of propagation by layers is commonly practised in the nurseries, in default of seed, and by it they most readily grow; for which purpose some stout plants for stools must be planted, which in a year after must be headed down near the bottom, that they may throw out many shoots near the ground, convenient for laying; which, in the autumn after they are produced, lie by for slit-laying, and by the autumn after will be well rooted, and form plants two or three feet high, so as to be separated, and planted in nursery rows like the seedlings. All the sorts will take tolerably by cutting off the strong young shoots; but the platanus occidentalis more freely than the oriental kind. Autumn is the best season; as soon as the leaf falls choose strong young shoots, and plant them in a moist soil; many of them will grow, and make tolerable plants by next autumn. To continue the distinction of the varieties more effectually, they should be propagated either by layers or cuttings; for, when raised from seed, those of the respective species generally vary. PLATE, n. s. & v. a. Sax. plat; Fr. plat; Belg. plate; Gr. #λarvç. A piece of metal beat out flat or into breadth; armour of plates; wrought silver or gold; a broad shallow eatingdish or vessel; to cover or arm with plates; beat into laminæ. The doors are curiously cut through and plated. Sandys. With their force they pierced both plate and mail, And made wide furrows in their fleshes frail. What nature wants has an intrinsick weight, All more is but the fashion of the plate. Young. PLATE is likewise used by sportsmen to express the reward given to the best horse at races; which was formerly often a piece of elegant silver plate, as a tea-pot, tea kitchen, caudle sally converted into a purse. cup or punch bowl; but is now almost univer PLATFORM, n. s. Fr. flat, plat and form. The sketch of any thing horizontally delineated; ichnography; scheme; plan; flat place. When the workmen began to lay the platform at Chalcedon, eagles conveyed their lines to the other side of the streight. Sandys. Their minds and affections were universally bent even against all the orders and laws wherein this church is founded, conformable to the platform of Geneva. Hooker. Where was this? Shakspeare, I have made a platform of a princely garden by precept, partly by drawing not a model, but some general lines of it. Bacon's Essays. They who take in the entire platform, and see the chain, which runs through the whole, and can bear in mind the observations and proofs, will discern how these propositions flow from them. Woodward. No artful wildness to perplex the scene: Grove nods at grove, each alley has a brother, And half the platform just reflects the other. Pope. PLATFORM, in the military art, is an elevation of earth, on which cannon are placed to fire ou the enemy; such are the mounts in the middle of curtains. On the ramparts there is always a platform, where the cannon are mounted. It is made by the heaping up of earth on the rampart, or by an arrangement of madriers, rising insensibly for the cannon to roll on, either in a casemate or on attack in the outworks. All practitioners are agreed that no shot can be depended on, unless the piece can be placed on a solid platform; for, if the platform shakes with the first impulse of the powder, the piece must likewise shake, which will alter its direction, and render the shot uncertain. They must be made higher behind than before by six or nine inches, to prevent too great a recoil, and to advance the gun easily when loaded. They are from eighteen to twenty feet long, eight feet before, and fourteen or fifteen feet behind, and the direction left to the officers of the royal regiment of artillery. PLATFORM, OF ORLOP, in a man of war, is a place on the lower deck, abaft the main mast, between it and the cock-pit, and round about the main capstan, where provision is made for the wounded men in time of action. PLATINA (Bartholomew Sacchi), or Philip, as others call him, a learned Italian historian, born in 1421 at Piedena, a village between Cremona and Mantua. He first embraced a military life, but afterwards devoted himself to literature. He went to Rome under Calixtus III. about 1456; was introduced to cardinal Bessarion, obtained some benefices from Pius II., and was appointed apostolical abbreviator. Paul II. succeeding, abolished the offices of all the abbreviators. Platina complained to the pope, and requested to be judged by the auditors of the Rota. Paul gave him a haughty repulse, and finally put him in prison, where he suffered great hardships for four months, when he was liberated, but forbid to leave Rome. After this he was again imprisoned with many others, on suspicion of a plot, and put to the rack. The plot being found imaginary, he was next accused of heresy. Sixtus IV., succeeding Paul in 1467, appointed Platina keeper of the Vatican library, in which station he lived very happily till 1481, when he died of the plague. He was author of several works, of which the most famous is his History of the Popes. PLATINA, or PLATINUM. See PLATINUM. PLATING. See SILVER.. PLATINUM, or PLATINA, in chemistry, is the heaviest of the metals. The name was given it by the Spaniards from the word plata, signifying silver, by way of comparison with that metal, whose color it resembles, or from the river Plata, near which it is found. It is characterised by a silvery color, not tarnished by the air; it is very hard and tenacious, sonorous, exceedingly malleable and ductile, specific gravity 21.5, detonating with nitre; soluble only by boiling it in sixteen times its weight of nitro-muriatic acid, and giving the solution first a yellow and then a red-brown color; its oxide is precipitated from this solution by the addition of muriate of ammonia, in the form of an orange powder. It is found in the gray silver ore of Guadalcanal in Spain, in Choco, in New Granada, and in the province of Barbacoas. It is peculiar to an al luvial tract of 600 leagues, where it is associated with grains of native gold, zircon, spinel, quartz, and magnetic ironstone. It is not true that this metal occurs near Carthagena, or Santa Fé, or in the islands of Porto Rico and Barbadoes, or in Peru, although these different localities have been mentioned by authors. The gray copper ore of Guadalcanal in Spain contains from one to ten per cent of platina. A Negro slave in the gold mines of Condoto, in the government of Choco, in South America, found a mass of platina of extraordinary magnitude, and which is now deposited in the royal museum, in Madrid. It weighs rather more than 14 lb., and is the largest piece of this metal hitherto met with The large specimen brought from America by Humboldt, and deposited in the king's cabinet in Berlin, and which weighs 1085 grains, w28 also found in Choco. These facts allow us to hope that platina may be found in its original repository somewhere in that country. It was unknown in Europe before the year 1748. Don Antonio Ulloa then gave the first intimation concerning its existence, in the narrative of his voyage with the French academicians to Peru. Its ore has been found to contain likewise four new metals-PALLADIUM, IRIDIUM, OsMIUM, and RHODIUM, which see; beside iron and chrome. The crude platina is to be dissolved in nitro-muriatic acid, precipitated by muriate of ammonia, and exposed to a very violent heat. Then the acid and alkali are expelled, and the metal reduced in an agglutinated state, which is rendered more compact by pressure while red-hot. Pure or refined platina is by much the heaviest body in nature. It is very malleable, though considerably harder than either gold or silver; and it hardens much under the hammer. Its color on the touch-stone is not distinguishable from that of silver. Pure platina requires a very strong heat to melt it; but, when urged by a white heat, its parts will adhere together by hammering. This property, which is distin guished by the name of welding, is peculiar to platina and iron, which resemble each other Îikewise in their infusibility. Platina is not altered by exposure to air; nei ther is it acted upon by the most concentrated simple acids, even when boiling, or distilled from it. The aqua regia best adapted to the solution of platina is composed of one part of the nitric and three of the muriatic acid. The solution does not take place with rapidity. A small quantity of nitric oxide is disengaged, the color of the fluid becoming first yellow, and af terwards of a deep reddish-brown, which, upon dilution with water, is found to be an intense yellow. This solution is very corrosive, and tinges animal matters of a blackish-brown color: it affords crystals by evaporation. Count Moussin Poushkin has given the following method of preparing malleable platina:Precipitate the platina from its solution by muriate of ammonia, and wash the precipitate with a little cold water. Reduce it in a convenient crucible to the well-known spongy metallic texture, which wash two or three times with boiling wa ter, to carry off any portion of saline matter that may have escaped the action of the fire. Boil it for about half an hour in as much water, mixed with one-tenth part of muriatic acid, as will cover the mass to the depth of about half an inch, in a convenient glass vessel. This will carry off any quantity of iron that might still exist in the metal. Decant the acid water, and edulcorate, or strongly ignite the platina. To one part of this metal take two parts of mercury, and amalgamate in a glass or porphyry mortar. This amalgamation takes place very readily. The proper method of conducting it is to take about two drachms of mercury to three drachms of platina, and amalgamate them together; and to this amalgam may be added alternate small quantities of platina and mercury, till the whole of the two metals is combined. Several pounds may be thus amalgamated in a few hours, and in the large way a proper mill might shorten the operation. As soon as the amalgam of mercury is made, compress it in tubes of wood, by the pressure of an iron screw upon a cylinder of wood adapted to the bore of the tube. This forces the superabundant mercury from the amalgam, and renders it solid. After two or three hours, burn upon the coals, or in a crucible lined with charcoal, the sheath in which the amalgam is contained, and urge the fire to a white heat; after which the platina may be taken out in a very solid state, fit to be forged. Muriate of tin is so delicate a test of platina, that a single drop of the recent solution of tin in muriatic acid gives a bright red color to a solution of muriate of platina, scarcely distinguishable from water. If the muriatic solution of platina be agitated with ether, the ether will become impregnated with the metal. This ethereal solution is of a fine pale yellow, does not stain the skin, and is precipitable by ammonia. If the nitro-muriatic solution of platina be precipitated by lime, and the precipitate digested in sulphuric acid, a sulphate of platinum will be formed. A subnitrate may be formed in the same manner. Platinum does not combine with sulphur directly, but is soluble by the alkaline sulphurets, and precipitated from its nitro-muriatic solution by sulphureted hydrogen. Pelletier united it with phosphorus, by projecting small bits of phosphorus on the metal heated to redness in a crucible; or exposing to a strong heat four parts each of platinum and concrete phosphoric acid with one of charcoal powder. The phosphuret of platinum is of a silvery-white, very brittle, and hard enough to strike fire with steel. It is more fusible than the metal itself, and a strong heat expels the phosphorus, whence Pelletier attempted to obtain pure platinum in this way. He found, however, that the last portions of phosphorus were expelled with too much difficulty. Platinum unites with most other metals. Added in the proportion of one-twelfth to gold, it forms a yellowish-white metal, highly ductile, and tolerably elastic, so that Mr. Hatchett supposed it might be used with advantage for watchsprings, and other purposes. Its specific gravity was 19.013. Platinum renders silver more hard, but its color more dull. Copper is much improved by alloying with platinum. From one-sixth to onetwenty-fifth, or even less, renders it of a golden color, harder, susceptible of a finer polish, smooth-grained, and much less liable to rust. Alloys of platinum with tin and lead are very apt to tarnish. For its important combinations with iron and steel, see STEEL. The following remarks of Mr. Murray on an easy method of forming alloys of platinum may not be unacceptable: While operating on antimony,' says Mr. M., 'I had placed a small button of that metal in a platinum spoon, and introduced it into the flame of a spirit lamp. The antimony had scarcely attained fusion, when the platinum spoon, together with it, ran into a uniform brittle mass, and fell in vivid combustion on the glass lamp, which was consequently fractured. The effect in question is better exhibited by wrapping up a bit of antimony in platinum foil, and holding it by a pair of forceps in the alcoholic flame, when a beautiful ignition shortly commences, and the glowing mass falls to the ground. Fragments of grained tin, arsenic, lead, bismuth, &c., folded up in platinum-foil, exhibited at the instant of fusion and combination very brilliant and beautiful phenomena; but the finest effect certainly was that of zinc and platinum-foil, when the fused mass emitted an intense light of a blue color. Alloys of tin and arsenic, bismuth and lead, &c., were in like manner subjected to experiment. Laminated gold, silver, and copper, proto-carburet, and per-carburet of iron, pinchbeck, &c., were rolled up in platinum-foil, and introduced into the flame, but without any particular result. Remarkable and beautiful, however, were the phænomena which appeared, when some metallic wires were brought in contact with platinum wire at a white heat in this flame. Gold, silver, and copper wires were those used. They fused in the flame, and, when brought in contact with the platinum wire, severally produced minute adhering balls, which, repeated with narrow intervals between, appeared ultimately like little glowing beads threaded on a string. These united with the platinum, and burned with very delicate scintillation; and, when the wire was inclined, the beads ran along the metallic string, combining with successive films of the wire, until the latter became as fine as the almost airy thread of the gossamer. The gold, silver, and copper wires, per se, entered into tranquil fusion, and did not scintillate. When zinc is carried along the platinum wire, the ends or streams of a fine blue flame ascend from it, and, when the bead rather exceeds in size, jets of a similar colored flame issue, accompanied sometimes with slight explosion.' Platinum, antimony, charcoal (fine levigated, from the betel-nut) and silica, when alloyed in a somewhat similar manner, gave a button impressed with difficulty by the knife, and granular. Crushed in a steel-mortar, it was reduced to powder, the particles of which were very brilliant. Platinum, silica, and antimony, nearly similar. Parts capable of imperfect extension by the hammer; and sometimes on the edge so hard |