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 ordinary merit. Curious if not very artistic bills have been produced in Russia; and in Austria good work has been done by Orlik, Schliessmann, Oliva and Hynais.

In the United States of America, however, with the exception of some designs by Matt Morgan, few posters of artistic interest were produced before 1889, in which year Louis J. Rhead commenced a notable series of decorative placards. Will H. Bradley began to produce his curious decorative grotesque posters a little later. If American artists are behind Europeans in the artistic designing of large posters they have no rivals in the production of small illustrated placards for publishers of books and magazines. Chief among those who have devoted themselves to this branch of poster design is Edward Penfield. Others who have achieved success in it include Maxfield Parrish, Ethel Reed, Will Carqueville, J. J. Gould, J. C. Leyendecker, Frank Hazenplug, Charles Dana Gibson, Will Denslow, Florence Lundbourg and Henry Mayer.

Exhibitions of artistic posters have been held in the chief cities of Europe and America, and the illustrated placard has already a literature of its own. In England a monthly magazine (The Poster) was for a time specially devoted to its interests, and collectors are numerous and enthusiastic.

See Ernest Maindron, Les Affiches illustrées (Paris, 1895); Les Maîtres de l’affiche (Paris); Les Affiches étrangères illustrées (Belgium, Austria, Great Britain, United States, Germany and Japan) (Paris, 1897); Charles Hiatt, Picture Posters (London, 1895); J. L. Spousel, Das Moderne Plakat (Dresden, 1897); Arsene Alexandre, M. H. Spielmann, H. C. Bunner and A. Jaccacci, The Modern Poster (New York, 1895).

 POSTERN (from O. Fr. posterne, posterle, Late Lat. posterula, small back-door, posterus, behind), a small gateway in the enceinte of a castle, abbey, &c., from which to issue and enter unobserved. They are often called “sally ports.” (See .)

 POSTHUMOUS, that which appears or is produced after the author or creator, and thus applied to a literary work or work of art published or produced after its author’s death, or especially to a child born after the death of its father. The Latin postumus, latest, last, from which the word is derived, is formed from post, after, but it was in Late Latin connected with humare, to place in the ground (humus), to bury.

 POSTICHE, a French term for a pretentious imitation, a counterfeit, particularly used of an inartistic addition to an otherwise perfect work of art. The French word was adapted from the Italian posticcio, from Latin positus, placed, added.

 POSTIL, or, properly a gloss on a scriptural text, particularly on a gospel text, hence any explanatory note on other writings. The word is also applied to a general commentary, and also to a homily or discourse on the gospel or epistle appointed for the day. The word in Medieval Latin was postilla, and this has been taken to represent ''post illa sc. verba textus'', i.e. “after these words of the text” (see Du Cange, Glossarium, s.v. postillae), but the form “apostil” may point to the Latin appositum, placed near or next to.

 POSTILION (through the Fr. from the Ital. postiglione), a postboy, rider of a post-horse, hence any swift messenger, but more particularly the rider of the near horse of a vehicle drawn by two or more horses where there is no driver. The swift travelling post chaises of the 18th and early 19th, centuries were usually driven by postilions.

 POSTUMIA, VIA, an ancient highroad of northern Italy, constructed in 148 by the consul Spurius Postumius Albinus. It ran from the coast at Genua through the mountains to Dertona, Placentia (the termination of the Via Aemilia Lepidi) and Cremona, just east of the point where it crossed the Po. From Cremona the road ran eastward to Bedriacum, where it forked, one branch running to the left to Verona and thence to the Brenner, the other to the right to Mantua, Altinum and Aquileia. The military occupation of Liguria depended upon this road, and several of the more important towns owed their origin largely to it. Cremona was its central point, the distances being reckoned from it both eastwards and westward.

 POSY (a shortened form of poesy, Fr. poésie, poetry), a verse of poetry or a motto, either with a moral or religious sentiment or message of love, often inscribed in a ring or sent with a present, such as a bouquet of flowers, which may be the origin of the common use of the word for a nosegay or bouquet. It has been suggested that this use is due to the custom of the symbolic use of flowers. Skeat quotes the title of a tract (Heber’s MSS. No. 1442), “A new yeare’s guifte, or a posie made upon certen flowers,” &c. “Posy rings,” plain or engraved gold rings with a “posy” inscribed on the inside of the hoops, were very frequently in use as betrothal rings from the 16th to the 18th centuries. Common “posies” were such lines as “In thee my choice I do rejoice,” “As God decreed so we agreed,” and the like. There are several rings of this kind in the British Museum.

<section end="Posy" /> <section begin="Potashes" />POTASHES, the crude potassium carbonate obtained by lixiviating wood ashes and evaporating the solution to dryness, an operation at one time carried out in iron pots—hence the name from “pot” and “ashes.” The term potash or caustic potash is frequently used for potassium hydroxide, whilst such a phrase as sulphate of potash is now appropriately replaced by potassium sulphate. (See .)

<section end="Potashes" /> <section begin="Potassium" />POTASSIUM [symbol K (from kalium), atomic weight 39·114 O＝16)], a metallic chemical element, belonging to the group termed the metals of the alkalis. Although never found free in nature, in combination the metal is abundantly and widely distributed. In the oceans alone there are estimated to be 1141$$\times$$1012 tons of sulphate, K2SO4, but this inexhaustible store is not much drawn upon; and the “salt gardens” on the coast of France lost their industrial importance as potash-producers since the deposits at Stassfurt in Germany have come to be worked. These deposits, in addition to common salt, include the following minerals: sylvine, KCl; carnallite, KCl·MgCl2·6H2O (transparent, deliquescent crystals, often red with diffused oxide of iron); kainite, K2SO4·MgSO4·MgCl2·6H2O (hard crystalline masses, permanent in the air); kieserite MgSO4·H2O (only very slowly dissolved by water); besides poly halite, MgSO4·K2SO4·2CaSO4·2H2O anhydrite, CaSO4; salt, NaCl, and some minor components. These potassium minerals are not confined to Stassfurt; larger quantities of sylvine and kainite are met with in the salt mines of Kalusz in the eastern Carpathian Mountains. The Stassfurt minerals owe their industrial importance to their solubility in water and consequent ready amenability to chemical operations. In point of absolute mass they are insignificant compared with the abundance and variety of potassiferous silicates, which occur everywhere in the earth’s crust; orthoclase (potash felspar) and potash mica may be quoted as prominent examples. Such potassiferous silicates are found in almost all rocks, both as normal and as accessory components; and their disintegration furnishes the soluble potassium salts which are found in all fertile soils. These salts are sucked up by the roots of plants, and by taking part in the process of nutrition are partly converted into oxalate, tartrate, and other organic salts, which, when the plants are burned, are converted into the carbonate, K2CO3. It is a remarkable fact that, although in a given soil the soda-content may predominate largely over the potash salts, the plants growing in the soil take up the latter: in the 'ashes of most land plants the potash (calculated as K2O) forms upwards of 90% of the total alkali. The proposition holds, in its general sense, for sea plants likewise. In ocean water the ratio of soda (Na2O) to potash (K2O) is 100:3·23 (Dittmar); in kelp it is, on the average, 100:5·26 (Richardson). Ashes particularly rich in potash are those of burning nettles, wormwood (Artemisia absinthium), tansy (Tanacetum vulgare), fumitory (Fumaria officinalis), and tobacco. In fact, the ashes of herbs generally are richer in potash than those of the trunks and branches of trees; yet, for obvious reasons, the latter are of greater industrial importance as sources of potassium carbonate. According to Liebig, potassium is the essential alkali of the animal body; and it may be noted that sheep excrete most of the potassium which they take from the land as sweat, one-third of the weight of raw merino consisting of potassium compounds.

To Sir Humphry Davy belongs the merit of isolating this element from potash, which itself had previously been considered an element. On placing a piece of potash on a platinum plate, connected to the negative of a powerful electric battery, and<section end="Potassium" />