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 son, that any chief who prepared to remove would be killed. At the Agency (Fort King, in Marion county) he became more violent, and in the summer of 1835 Thompson put him in irons. From this confinement he obtained his release by a profession of penitence and of willingness to emigrate. Late in November 1835 he murdered Charley Emathla (or Emartla), a chief who was preparing to emigrate with his people, and on the 28th of December he and a few companions shot and killed General Thompson. On the same day two companies of infantry under Major Francis L. Dade were massacred at the Wahoo Swamp near the Withlacoochee river, while marching from Fort Brooke on Tampa Bay to the relief of Fort King. In a battle fought three days later at a ford of the Withlacoochee, Osceola was at the head of a negro detachment, and although the Indians and negroes were repulsed by troops under General Duncan L. Clinch (1787–1849), they continued, with Osceola as their most crafty and determined leader, to murder and devastate, and occasionally to engage the troops. In February 1836 General Edmund P. Gaines (1777–1849), with about 1100 men from New Orleans, marched from Fort Brooke to Fort King. When he attempted to return to Fort Brooke, because there were not the necessary provisions at Fort King, the Indians disputed his passage across the Withlacoochee. In the same year Generals Winfield Scott and Richard K. Call (1791–1862) conducted campaigns against them with little effect, and the year closed with General Thomas Sidney Jesup (1788–1860) in command with 8000 troops at his disposal. With mounted troops General Jesup drove the enemy from the Withlacoochee country and was pursuing them southward toward the Everglades when several chiefs expressed a readiness to treat for peace. In a conference at Fort Dade on the Withlacoochee on the 6th of March 1837 they agreed to cease hostilities, to withdraw south of the Hillsborough river, and to prepare for emigration to Arkansas, and gave hostages to bind them to their agreement. But on the 2nd of June Osceola came to the camp at the head of about 200 Mikasuki (Miccosukees) and effected the flight of all the Indians there, about 700 including the hostages, to the Everglades. Hostilities were then resumed, but in September Brigadier General Joseph M. Hernandez captured several chiefs, and a few days later there came from Osceola a request for an interview. This was granted, and by command of General Jesup he was taken captive at a given signal and carried to Fort Moultrie, at Charleston, South Carolina, where he died in January 1838. The war continued until 1842, but after Osceola's death the Indians sought to avoid battle with the regular troops and did little but attack the unarmed inhabitants. See J. T. Sprague, The Origin, Progress and Conclusion of the Florida War (New York, 1848).

OSCHATZ, a town in the kingdom of Saxony, in the valley of the Döllnitz, 36 m. N.W. of Dresden, on the trunk railway to Leipzig. Pop. (1905) 10,854. One of its three Evangelical churches is the handsome Gothic church of St Aegidius, with twin spires. Sugar, felt, woollens, cloth and leather are manufactured, and there is considerable trade in agricultural produce. Four miles west lies the Kolmberg, the highest eminence in the north of Saxony.

 OSCHERSLEBEN, a town of Germany, in the Prussian province of Saxony, on the Bode, 24 m. by rail S.W. of Magdeburg, and at the junction of lines to Halberstadt and Jerxheim. Pop. (1905) 13,271. Among its industrial establishments are sugar-refineries, iron-foundries, breweries, machine-shops and brick works. Oschersleben is first mentioned in 803, and belonged in the later middle ages to the bishops of Halberstadt.

 OSCILLA, a word applied in Latin usage to small figures, most commonly masks or faces, which were hung up as offerings to various deities, either for propitiation or expiation, and in connexion with festivals and other ceremonies. It is usually taken as the plural of oscillum (dimin. of os), a little face. As the oscilla swung in the wind, oscillare came to mean to swing, hence in English “ oscillation,” the act of swinging backwards and forwards, periodic motion to and fro, hence any variation or fluctuation, actual or figurative. For the scientific problems connected with oscillation see and.

Many oscilla or masks, representing the head of Bacchus or of different rustic deities, are still preserved. There is a marble oscillum of Bacchus in the British Museum. Others still in existence are made of earthenware, but it seems probable that wax and wood were the ordinary materials. Small rudely shaped figures of wool, known as pilae, were also hung up in the same way as the oscilla.

 OSCILLOGRAPH. In connexion with the study of alternating or varying electric current, appliances are required for determining the mode in which the current varies. An instrument for exhibiting optically or graphically these variations is called an oscillograph, or sometimes an ondograph. Several methods have been employed for making observations of the form of alternating current curves—(1) the point-by-point method, ascribed generally to Jules Joubert; (2) the stroboscopic methods, of which the wave transmitter of H. L. Callendar, E. B. Rosa, and E. Hospitalier are examples; (3) methods employing a high-frequency galvanometer or oscillograph, which originated with A. E. Blondel, and are exemplified by his oscillograph and that of W. Duddell; and (4) purely optical methods, such as those of I. Frohlich and K. F. Braun.

In the point-by-point method the shaft of an alternator, or an alternating current motor driven in step with it, is furnished with an insulating disk having a metallic slip inserted in its edge. Against this disk press two springs which are connected together at each revolution by the contact of the slip at an assigned instant during the phase of the alternating current. This contact may be made to close the circuit of a suitable voltmeter, or to charge a condenser in connexion with it, and the reading of the voltmeter will therefore not be the average or effective voltage of the alternator, but the instantaneous value of the electromotive force corresponding to that instant during the phase, determined by the position of the rotating contact slip with reference to the poles of the alternator. If the contact springs can be moved round the disk so as to vary the instant of contact, we can plot out the value of the observed instantaneous voltage of the machine or circuit in a wavy curve, showing the wave form of the electromotive force of the alternator. This process is a tedious one, and necessarily only gives the average form of thousands of different alternations.

In the Hospitalier ondograph, a synchronous electric motor driven in step with the periodic current in the circuit being tested drives a cylinder of insulating material having a metallic slip let into its edge. This cylinder is driven at a slightly lower speed than that of synchronise. Three springs press against the cylinder and make contact for a short time during each revolution, so that a condenser is charged by the circuit at an assigned instant during the alternating current phase, and then subsequently connected to a voltmeter. This process, so to speak, samples or tests the varying electromotive force of the alternating current at one particular instant during the phase and measures it on a voltmeter. Owing to the fact that the cylinder is losing or gaining slightly in speed on the circuit periodicity, the voltmeter goes slowly, say in one minute, through all the phases