Potash Water of from wood ashes. What is known as caustic potash (hydrate of potassium, KHO) is prepared from ordinary potash. It is solid, white, and extremely caustic, eating into animal and vegetable tissues with great readiness. It changes the purple of violets to green, restores reddened litmus to blue, and yellow turmeric to reddish brown. It rapidly attracts humidity from the air, and becomes semifluid. It is fusible at a heat of 300°, and is volatilized at low ignition. It is used in surgery under the name of lapis infernālis or lapis causticus for destroying warts, fungoid growths, etc., and may be applied beneficially to the bites of dogs, venomous serpents, etc. In chemistry it is very extensively employed, both in manufactures and as an agent in analysis. It is the basis of the common soft soaps, for which purpose, however, it is not used in its pure state. See Potassium. Potash Water, an water produced by mixing bicarbonate of potash with carbonic acid water in the proportion of 20 grains to each bottle of the water, or about half an ounce to the gallon. Bisulphate of potash, as being cheaper than tartaric acid, is sometimes used (but should not be) with carbonate of soda to produce the common effervescing drink. A valuable medicinal water is compounded of a certain proportion of bromide of potassium. See Aerated Waters. aerated Potato ash,' and closely resembles common salt (chloride of sodium). It is obtained from potassic minerals, the ashes of marine plants (kelp), and from seawater or brine springs. It enters into the manufacture of saltpeter, alum, artificial manures, etc. Bromide and iodide of potassium are useful drugs. (For the carbonate of potassium see Potash.) Bicarbonate of potassium is obtained by exposing a solution of the carbonate to the air, carbonic acid being imbibed from the atmosphere, and crystals being deposited; or it is formed more directly by passing a current of carbonic acid gas through a solution of the carbonate of such a strength that crystals form spontaneously. It is much used in medicine for making effervescing drinks. Nitrate of potassium is niter, or saltpeter. (See Niter.) Sulphate of potassium (K2SO4) is used medicinally as a mild laxative, in making some kinds of glass and alum, and in manures. The bisulphate (KHSO.) is used as a chemical reagent, and in calico-printing and dyeing. Chlorate of potassium (KCIO3) is employed in the manufacture of lucifer matches, in certain operations in calicoprinting, and for filling friction-tubes for firing cannon. It is a well-known source of oxygen. The bichromate (K:Cr:O) is also used in calico-printing and dyeing. Cyanide of potassium (KČN) is much used in photography. Potasium (po-tas'i-um; a Latinized Potato (po-tātō: Solanum tuberōterm from potash), a sum), a plant belonging to the name given to the metallic basis of pot- nat. order Solanaceae, which also includes ash, discovered by Davy in 1807, and one such poisonous plants as nightshade, henof the first fruits of his electro-chemical bane, thorn-apple and tobacco. We owe researches; symbol, K; atomic weight, 39.1. Next to lithium it is the lightest metallic substance known, its specific gravity being 0.865 at the temperature of 60°. At ordinary temperatures it may be cut with a knife and worked with the fingers. At 32° it is hard and brittle, with a crystalline texture; at 50° it becomes malleable, and in luster resembles polished silver; at 150° it is perfectly liquid. Potassium has a very powerful affinity for oxygen, which it takes from many other compounds. A freshly exposed surface of potassium instantly becomes covered with a film of oxide. metal must therefore be preserved under a liquid free from oxygen, rock-oil or naphtha being generally employed. It conducts electricity like the common metals. When thrown upon water it decomposes that liquid with evolution of hydrogen, which burns with a pale violet flame, owing to the presence in it of potash vapor. Chloride of potassium (KCI) is known in commerce as muriate of pot The Tubers of Potato. this esculent to western South America, where it still grows wild, chiefly in the region of the Andes, producing small, Potato tasteless, watery tubers. The potato was first introduced into Europe by the Spaniards after the conquest of Peru, by whom it was spread over the Netherlands, Burgundy, and Italy before the middle of the sixteenth century. In Germany it is first heard of as a rarity in the time of Charles V. Sir John Hawkins, Sir Francis Drake, and Sir Walter Raleigh are all credited with the first introduction of the tuber into England (1565). Although the potato was tolerably widely distributed on the continent of Europe before its appearance in Britain, it seems to have been cultivated more as a curiosity than as an article of food, and Ireland is said to have been the country in which it was first cultivated on a large scale for food. In the course of the eighteenth century it became a favorite article of food with the poorer classes in Germany; but in France there existed so violent a prejudice against it that it did not come into general use until towards the end of the century. The potato is a perennial plant, with angular, herbaceous stems, growing to the height of 2 or 3 feet; leaves pinnate; flowers pretty large, numerous, disposed in corymbs, and colored violet, bluish, reddish, or whitish. The fruit is globular, about the size of a gooseberry, reddish brown or purplish when ripe, and contains numerous small seeds. The tubers, which furnish so large an amount of the food of mankind, are really underground shoots abnormally dilated, their increase in size having been greatly fostered by cultivation. Their true nature is proved by the existence of the eyes' upon them. These are leaf-buds, from which, if a tuber or a portion of it containing an eye is put into earth, a young plant will sprout, the starchy matter of the tuber itself supplying nutriment until it throws out roots and leaves, and so attains an independent existence. The potato succeeds best in a light, sandy loam containing a certain proportion of vegetable matter. The varieties are very numerous, differing in the time of ripening, in their form, size, color, and quality. New ones are readily procured by sowing the seeds, which will produce tubers the third year, and a full crop the fourth. But the plant is usually propagated by sowing or planting the tubers, and it is only in this way that any one variety can be kept in cultivation. Like all plants that are extensively cultivated, and under very different circumstances of soil, climate, and artificial treatment, the potato is extremely subject to disease. Potato-bug structive potato disease proper. The principal feature of the curl is the curling of the shoots soon after their first appearance. After that they make little progress, and sometimes disappear altogether. The plants produce no tubers, or only a few minute ones, which are unfit for food. The scab is a disease that attacks the tubers, which become covered with brown spots on the outside, while underneath the skin is a fungus called Tubercinia scabies. The dry rot is characterized by a hardening of the tissues, which are completely gorged with mycelium (the vegetative part of fungi). In the disease called wet rot the potato is affected much in the same way as by the dry rot; but the tubers, instead of becoming hard and dry, are soft. The fungus present in wet rot is supposed to be the same that accompanies dry rot. The potato disease par excellence was prevalent on both sides of the Atlantic in the year 1845. Usually the first sign of this disease is the appearance of brown patches upon the haulms and leaves. These spots appear about the time the plants attain their full growth, and when carefully examined are found to be surrounded by a ring of a paler color. The whole of this outer ring is infested with a fungus called the Botrytis or Peronospora infestans, which is a constant accompaniment of the disease, if not its cause. If the weather be dry the progress of the disease is slow, but if a moist warm day supervene it will be found that the mold spreads with great rapidity, and sometimes the whole plant becomes putrid in a few days. The disease first shows itself in a tuber by appearing as a brownish spot, and the part affected may be cut out, leaving the remainder quite wholesome. None of the plans adopted for mitigating the potato disease have been very effective. The potato is also attacked by various insects, the most destructive being the Colorado beetle. The tubers consist almost entirely of starch, and being thus deficient in nitrogen, should not be too much relied on as a staple article of diet. Potatoes are extensively used as a cattle-food, and starch is also manufactured from them. In Maine, Vermont, and Northern New York this is an important industry. Enormous crops of this valuable esculent are grown in the United States, and much attention has been given to their improvement. Its cultivation has also extended widely over the earth. Potato-bug, ica to the Colorado bee a name given in Amer Among the diseases to which it is liable are the curl,' the scab,' the dry rot,' tle (which see), from the injury caused and the 'wet rot,' besides the more de- by it to the potato. Potchefstroom Pot Metal (pot'shef-strōm), a which might be done by the falling of Potchefstroom (pot'shef-ström), town in the Trans- the stone to the surface of the earth. that mood of a verb which exvaal, South Africa, on the Mooi River, Potential Mood, presses an action, event, or circumstance as merely possible, formed in English by means of the auxiliaries may or can. herbaceous perennials, nat. Potentilla (po-ten-til'a), a genus of order Rosacea, found chiefly in the temperate and cold regions of the northern hemisphere, containing about 120 species. They are tall or procumbent herbs, rarely undershrubs, with digitate or unequally pinnate leaves, and yellow, red, white flowers. Some purple, favorite garden flowers. P. anserina is also called silver-weed, goose-grass, wild tansy, the leaves of which are greedily devoured by geese; and P. fragariastrum, barren strawberry. P. reptans is a well-known creeping plant with conspicuous yellow flowers. The roots of P. P. Tormentilla is used in anserina are eaten in the Hebrides, either raw or boiled. Lapland and the Orkney Islands both to It is also employed in tan and to dye leather, and also to dye worsted yarn. medicine as a gargle in the case of enlarged tonsils and other diseases of the throat, and for alleviating gripes in cases or about 25 miles N. of the Vaal River. Potenza (po-tent'så), a are or town of Southern Italy and a bishop's see, capital of the province of the same name, on a hill of the Apennines near the Basento, 85 miles E. S. E. of Naples. It is walled, and is indifferently built. It suffered severely by earthquake in 1857, most of the buildings having fallen and many lives were lost. Pop. (1911) 16,672.-The province is partly bounded by the Gulf of Taranto and the Mediterranean. Its chief productions are maize, hemp, wine, silk, cotton. Poterium plants, nat. order Rosaces (pō-te'ri-um), a genus of and suborder Sanguisorbeæ. P. Sanguisorba, or salad-burnet, which grows on dry and most frequently chalky pastures, is said to be native about Lake Huron. It is valuable for fodder, and is used in It has pinnate leaves and tall salad. stems surmounted by dense heads of small flowers. Potential Energy, the energy of Poti (po'tye), a Russian town in that part of a system of bodies which is due to their eastern on the Transcaucasia, It has extensive coast of the Black Sea. harbor works, and is connected by railway with Tiflis, but the trade is being drawn away by Batoum. Pop. 7666. an inferior kind of brass is at a certain height above the earth's Pot Metal, copper, 10 parts; lead, Also a kind 6 to 8), used for making various large vessels employed in the arts. Potocki of stained glass in which the colors are incorporated with the substance by being added while the glass is in a state of fusion. Potocki (po-tots'ki), an ancient Polish family, taking its name from the castle of Potok, and still holding possessions in Galicia and the Ukraine. Among its most distinguished members was Count Ignatius, grand marshal of Lithuania before the downfall of Poland, and a fellow-patriot of Kosciusko, born 1751. In 1791 he took refuge in Saxony, and published a political tract upon the establishment and fall of the constitution, returning, however, to share in the last struggle for independence. He then passed some time in the prisons of St. Petersburg and Warsaw, and died at Vienna 1809. Potomac (po-to'mak), a river which forms the boundary between Maryland and Virginia, passes Washington, and after a course of nearly 400 miles flows into Chesapeake Bay, being about 8 miles wide at its mouth. The termination of the tidewater is at Washington, about 125 miles from the sea, and the river is navigable for large ships for that distance. Above Washington are several falls which obstruct navigation. Pot'oroo. See Kangaroo Rat. Potosi (pot-o-se'; common pronunciation, po-to'sē), a city of Southern Bolivia, in the department of same name, on the slope of the mountain mass of Cerro de Pasco, more than 13,000 feet above the sea-level, in bare and barren surroundings. It is regularly built, and has a cathedral, a mint, etc. It has long been celebrated for its silver mines, which were at one time exceedingly productive, and have again begun to show an improved return. The city was founded in 1547, and the nopulation increased so rapidly that in 1611 it amounted to 150,000, but the 1906 estimate was 23,450.-The department has an area of 50,000 square miles, and is celebrated for 1ts mineral wealth, especially silver. Pop. 325,615. Pot-pourri (po-pö-re: French) sig Potter lin, on the Havel, which here has several lakes connected with it. It is, on the whole, one of the handsomest and most regularly built towns in Germany, and with its suburbs now covers a large space. The principal edifices are the royal palace (remodeled 1750), with interesting memorials of Frederick the Great; Garrison Church, containing the tombs of William I and Frederick the Great; the Nikolai Church, the French Protestant Church, built after the model of the Pantheon at Rome; the town-house; and the Barberini Palace, erected by Frederick the Great in imitation of that at Rome, but rebuilt in 1850-52. Immediately to the west, outside the Brandenburg Gate (resembling a Roman triumphal arch), are the palace and park of Sans Souci. The palace, a building of one story, was erected under the direction of Frederick the Great; the grounds are finely laid out, and contain various fountains, etc., and an orangery 330 yards long. In the same neighborhood is the New Palace, a vast brick building exhibiting much gaudy magnificence. A third palace in the environs of the town is called the Marble Palace. Potsdam was an unimportant place till the Great Elector selected it as a place of residence and built the royal palace (1660-71). Pop. (1910) 62,243. Potstone (pot'ston; Lapis ollāris), a species of talc containing an admixture of chlorite. Its color is green of various shades; it is greasy and soft, but becomes hard on being exposed to the air. It derives its name from its capability of being made into vases, etc., by turning. It was obtained by the ancients from quarries in the island of Siphnos and in Upper Egypt. It is now quarried in the Valais in Switzerland, in Norway, Sweden, Greenland, and the neighborhood of Hudson Bay. Pott (pot), AUGUST FRIEDRICH, a German philologist, born in 1802. He studied at Göttingen, became a teacher in the gymnasium at Celle, and subsequently privat-docent in the University of Berlin. He wrote Researches in the Etymology of the Indo-Germanic LanHe died in 1887. guages, etc. nifies the same as olla Potter podrida (which see); also, and more generally, a musical medley, or a literary composition made up of parts put together without unity or bond of connection. Potsdam (pots'dam), a town in Prussia, a bishop's see, capital of the province of Brandenburg, and the second royal residence of the kingdom, is charmingly situated in the midst of (pot'èr), HENRY CODMAN, author and divine, was born at Schenectady, New York, in 1835. He entered the Protestant Episcopal ministry, and became bishop of New York City in 1887. He published numerous works and was an energetic social reformer. In 1900 he visited the Philippines and published his views thereon. He died in 1908. JOHN, an English classical Wooded bills, 17 miles southwest of Bert Potter, scholar and divine, primate of Potter all England, born in 1674, was the son of a linen-draper of Wakefield. In 1706 he became chaplain to Queen Anne. In 1708 he was appointed regius professor of divinity at Oxford, in 1715 was raised to the see of Oxford, and in 1737 appointed Archbishop of Canterbury. He died in 1747. His works include Archæologia Græca, a work on Greek antiquities, A Discourse on Church Government (1707), an edition of Clemens Alexandrinus (1714), and theological works (Oxford, 1753). Potter, PAUL, a celebrated Dutch painter of animals, born at Enkhuisen in 1625. He received his first instruction in art from his father, Pieter Potter (1587-1655), a painter of some note. He devoted himself specially to the study of animals, producing his firstsigned picture, The Herdsman, in 1613. His works, specimens of which are in the more important European galleries, are highly esteemed. His coloring is brilliant, and the separate parts are delicately executed, yet without stiffness or mannerism. His pictures are generally of small size, but there is a celebrated one of large size in Pottery was long supposed to be of no older date than the ninth century of our era, and to have originated with the Arabs in Spain; but the discovery of glazed ware in Egypt, of glazed bricks in the ruins of Babylon, of enameled tiles and glazed coffins of earthenware in other ancient cities, proves that this is not the case. The Arabs, however, seem to be entitled to the credit of having introduced the manufacture of glazed ware into modern Europe. The Italians are said to have become acquainted with this kind of ware as it was manufactured in the island of Majorca, and hence they gave it the name of majolica. They set up their first manufactory at Faenza in the fifteenth century. In Italy the art was improved, and a new kind of glaze was invented, probably by Luca della Robbia. The French derived their first knowledge of glazed ware from the Italian manufactory at Faenza, and on that account gave it the name of faïence. About the middle of the sixteenth century the manufactory of Bernard Palissy at Saintes in France became famous on account of the beautiful glaze and rich ornaments by which its products were distinguished. A the museum of Successive stages of Earthenware Vessel on the little later the The Hague. It represents a man Potter's Wheel. and cattle, with a bull in the foreground, and is known as Paul Potter's bull. He died at Amsterdam in 1654, at the early age of twenty-nine. His engravings are much esteemed, and his paintings command a high price. See Clay. Potter's Clay. vessels or utensils of any sort in clay. This art is of high antiquity, being practiced among various races in prehistoric times. We find mention of earthenware in the Mosaic writings. The Greeks had important potteries at Samos, Athens, and Corinth, and attained great perfection as regards form and ornamen tation. Demaratus, a Greek, the father of Tarquinius Priscus, king of Rome, is said to have instructed the Etruscans and Romans in this art. Glazed earthenware Dutch began to manufacture at Delft the more solid but less beautiful ware which thence takes its name. The principal improver of the potter's art in Britain was Josiah Wedgwood in the eighteenth century. Porcelain or chinaware first became known in Europe about the end of the sixteenth century through the Dutch, who brought it from the East. See Faience and Chinaware. The Though the various kinds of pottery and porcelain differ from each other in the details of their manufacture, yet there are certain general principles and processes which are common to them all. first operations are connected with the preparation of the potter's paste, which consists of two different ingredients, an earthy substance, which is the clay proper; and a siliceous substance, which is necessary to increase the firmness of the ware, and render it less liable to |