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OThe history of the symbol O is parallel to that of E. Each represents several sounds which are dis tinguished habitually in speech without any difficulty, but for which, owing to the imperfection of the English alpha bet, there are no separate symbols. Probably the confusion is worst in English ; but French and Italian also have more sounds for each of these symbols than can be properly included under them, and so they distinguish these some times by diacritical marks, as d or 6, and sometimes they do not distinguish at all. The different sounds which O is used to denote in English lie, with one exception, on the line between the pure a -sound and the pure u- sound. We have already seen that e denotes several different sounds on the other line that between pure a and pure i. The difference be tween the sounds on these two lines is this. In the a i line only the tongue is employed ; it is raised more and more for each successive sound. But in the a u line the tongue is not the only agent ; the cavity of the mouth is also contracted, so that the passage is narrowed, and the lip -aperture is lessened more and more for each sound; in technical phrase the lips are "rounded," so that for u the aperture is the smallest possible to allow of the utter ance of a true vowel, hence the great ease with which the -sound passes into a w, in which there is friction caused by the still greater closing of the lips, and therefore we have a consonant not a vowel sound. The following different sounds denoted by O in English are readily discriminated. Beginning from the -end of the line, we come first to the sounds heard in " not " and in " lord " ; for both of these the back of the tongue is much depressed and the lips are only slightly rounded. The difference between the two sounds consists in this for the first the back of the tongue is more con vex than for the second ; the passage is therefore some what narrowed, and the two corresponding sounds are therefore (here and in all the other similar pairs) known technically as " narrow " and "wide," or as "open "and "close." The narrow sound is written by o in English when r or I follows, and the wide is written aw as in " law," or au as in " Paul," or even a as in " pall." The next pair may be exemplified by "pole" and "pour," narrow and wide respectively; for these the tongue is higher and the rounding greater. Here again several digraphs represent the same sound, as in " foal," " soul," "hoe," "grow." Next the doubled o is generally used to represent the last sound in the scale, the close u, for which the tongue is highest and the "rounding" greatest, as in " pool " ; but in " rule " and others the same symbol is used for this sound as would be used in other European languages. Lastly the exception mentioned above o is one of the symbols employed to denote the neutral vowel, as in " son," as well as u in " sun " and a in " final." The modified German o written o or oe is a sound unknown in English. It is produced by putting the tongue into the position for the sound denoted by a in " fate " or e in " fete " a middle sound in the line between a and i and then by rounding the lips. It thus com bines the specialities of the two scales of vowel -sound the i- scale and the u- scale. In Italian there are an " open " o (marked <5) and a "close" o (marked o). The "open" o corresponds to the open or wide sound described above. The " close " o is not quite the same as the "narrow" o of English, but comes a little nearer to u. In the form of the symbol there is no recorded variation, except that in old Latin it was sometimes square, as O. In Greek two symbols were employed and ft for short and long o respectively. But it is not improbable that the second of these denoted at first not merely long o but a more open sound, more near to the sound of " law " in English. OAJACA, or OAXACA, the chief town of the province of the same name in Mexico, lies 1600 feet above the sea in a beautiful valley on the left bank of the Atoyac, or Eio Verde, which reaches the Pacific after a course of about 170 miles. The city is surrounded by luxuriant gardens, orchards, and cochineal plantations ; its streets are wide and regular, and among its public buildings are the cathedral, the bishop s palace (fashioned after the type of a similar ancient edifice at Mitla), and the Dominican monastery and church. Chocolate, cigars, cotton -cloth, wax candles, etc., are manufactured. The population was 26,228 in 1877. The city, which dates from 1522, was visited by a severe earthquake in 1870. OAK (Anglo-Saxon, ac or a?c), a word found, vari ously modified, in all Germanic languages, and applied to plants of the genus Quercus, a well-marked section of the natural order Corylaceaz (Cupuliferai of De Candolle), in cluding some of the most important timber trees of the north temperate zone. All the species are arborescent or shrubby, varying in size from the most stately of forest trees to the dwarfish bush. Monoecious, and bearing their male flowers in catkins, they are readily distinguished from the rest of the Cupuliferous family by their peculiar fruit, an acorn or nut, enclosed at the base in a woody cup, formed by the consolidation of numerous involucral bracts developed beneath the fertile flower, simultaneously with a cup -like expansion of the thalamus, to which the bracteal scales are more or less adherent. The ovary, three-celled at first, but becoming one-celled and one-seeded by abortion, is closely invested by the perianth, toothed on 9^ FIG. 1. Inflorescence of Oak. a, 6, c, Querc-us Robur. (From Behrens , Allge- meine Botanil; pp. 209, 210.) d, e, Q. sessiliftora (Smith); half natural size. (From Kotschy, Die Eichen Europa s, Vienna, 1862, plate xxxn.) the margin, and adherent below ; the male flowers are in small clusters on the usually slender and pendent stalk, forming an interrupted catkin ; the stamens vary from six to twelve. The alternate leaves are more or less deeply sinuated or cut in most of the species, but in some of the deciduous and many of the evergreen kinds are nearly or quite entire on the margin. The oaks are widely distri buted over the temperate parts of Europe, Asia, North Africa, and North America. In the western hemisphere they range along the Mexican highlands and the Andes far into the tropics, while in the Old World the genus, well XVII. 87
