O.
Oak′um.
(Anglo-Saxon, acumba.) 1. The coarse portion separated from strick (strike: A.-S., strican) of flax or hemp in hackling. 2. Untwisted rope; used for calking the seams of a ship's plank, being forced thereinto by chisel and mallet. A first-rate ship of war requires 67,000 pounds of oakum to close the seams.Oar.
1. (Nautical.) An instrument for rowing. A long paddle which rests in tholes on the gunwale in rowing. A long oar, used occasionally to assist a vessel in a calm, is a sweep, and is operated by two or more men. Small oars are sculls; one rower wielding a pair, sitting midlength of the thwart. Scalling a boat is performed by an oar shipped in a half-round hole at the stern, the oar being moved with a twisting action from side to side. A rigged oar is one in which the oar is pivoted to the gunwale and moved by a rod, or otherwise by a rower sitting abaft it, so that he may face forward. The blade of the oar, also known as the wash, is the broad flat part which is dipped into the water in rowing. The blade was formerly known as the pala, which survives in the term peel, yet applied to it. The term pala meant a spade; the older forms of paddles might be used for digging. The loom of the oar is the shaft, beginning at the blade, and terminating in the handle, which is of rather smaller diameter than the loom, in order to afford a good hand-hold to the rower. The oar when in use rests in rowlocks in the gunwale of the boat or between thole-pins, which are round pegs, inserted in holes bored in the gunwale. To boat oars means to cease rowing and lay the oars in the boat. To feather oars is to turn the blades in a horizontal position on lifting them from the water at the end of each stroke, to afford as little resistance as possible to the water in withdrawing, and to the air. To ship oars is to place them in the rowlocks or between the thole-pins, ready for use. An oar is frequently used for steering; in which case it is sometimes an ordinary oar shipped in a swiveled fork at the stern, as in whale-boats; or it may be a broad paddle attached to a long arm, working on a swivel near its center, or similar device, as is often the case in keel-boats, scows, etc. To lie on the oars is to raise them from the water and hold them horizontally. To muffle the oars is to put sheepskins in the rowlocks to prevent any sound in rowing. To toss the oars is to raise them vertically, resting on the handles. It is a form of salute. To unship the oars is to take them out of the rowlocks. Single-banked is when the oars are rowed, one to each thwart, starboard and port sides alternately. Double-banked is when two opposite oars are pulled by two rowers seated on the same thwart, or by two men at each oar. The term bank, as applied to galleys, meant a tier of oars, as double-banked, single-banked, etc. Says Pliny: “The Copae invented the oar, and the Plataeans gave it its broad blade.” We suppose he means a fair distinction between the oar which rests in tholes and the paddle which is handled without receiving a fulerum support on the gunwale. The great ship of Ptolemy Philopator had forty ranks of rowers; the oars of the longest row were 38 cubits in length (say, 57 feet). These were loaded with lead on the part inside of the rowlocks, so as to evenly balance. The scarcity of timber in Eastern lands had a great deal to do with the importance and peace of nations thereabouts. The possession of Lebanon and Bashan was not one of the least of the points in dispute between the two branches of the Macedonian Empire represented by the Seleucidae and the Ptolemies. These struggles fill up the time between the death of Alexander and the absorption of the country by the Romans, and form the history which was so remarkably portrayed in prophency by Daniel several hundred years before. See the 11th chapter of Daniel. While the fir-trees of Senir furnished the planks, and the cedars of Lebanon the masts, the oaks of Bashan contributed the oars of the famous galleys of Phoenicia. Being the great carriers of that day, and having direct dealings with Britain, India, Greece, Spain, Africa, and many ports whose names remain but whose localities are difficult to determine, these “princes of the sea” and artificers upon the land were in demand wherever an extra amount of intelligence, taste, skill, and daring was required. Two lands at least contributed the timber of their vessels, another the cordage, another the sails, another the oars, others the ivory, ebony, and sandalwood for adorument; Palestine contributed its iron. Copper from the same land and the Caucasus was mingled with the tin from the far-off Cassiterides, the first contribution of Britain to the common stock of the world's merchandise, and which had the honor of forming with copper the alloy which made the brazen (bronze) laver and furniture of Solomon's Temple. Though littoral Tyre was destroyed by Nebuchadnezzar, and insular Tyre by “young Ammon,” the “rough he-goat, the king of Grecia,” yet she survived in her colonies until the Roman maelstrom drew them all into its vortex and swamped the distinctiveness of many nations. The best picture of the time is that given in Ezekiel XXVII. (which see). Machines are made for dressing, planing, riving, and splitting oars, but do not differ so specially from machines for getting out and dressing stuff for other purposes as to require elaborate description here.
2. (Brewing.) A blade or paddle with which mash is stirred in the tun.
Oar-lock.
（Nautical.) A means of pivoting an oar on the gunwale. A rowlock (which see).
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| Oar-propeller. |
Oar-pro-pel′ler.
1. A device to imitate by machinery the action of sculling. Two submerged blades at the stern are attached to an oscillating, vertical shaft and brought broadside to the water and feathered, alternately, so as to make an effective and a return stroke. The horizontal shaft [1542] |
| Oar-swivel. |
Oar-swiv′el.
A pivotal device for an oar on the gunwale. A rowlock. In the example, the oar is hung in gimbals, which allow it vibration in any plane, and it has besides a capacity for rotation on its own longitudinal axis in feathering. See rowlock.Oast.
A hop-drying kiln. |
| Oast. |
Ob′e-lisk.
1. A quadrangular, slender stone shaft, with a pyramidal apex. The width of the base is usually about one tenth of the hight, and the pyramidal apex has about one tenth of the whole length. It is Egyptian in its conception and execution. Obelisks were erected in pairs, and are yet numerous on the ancient sites, and no doubt many prostrate ones are buried in the soil of Egypt, which has risen from the deposit of the Nile 9 feet in 1,700 years at Elephantine, and 7 feet at Thebes. The deposit of mud at Thebes, therefore, since Amunoph I., would be about 17 feet. There are about a dozen Egyptian obelisks erected in Rome. The largest is that from Heliopolis. It is of granite, and now stands before the north portico of the Church of St. John Lateran, where it was erected in 1588. Its whole hight is about 149 feet; without the base, 105 feet. It was removed to Alexandria by Constantine, and to Rome by his son Constantius, and placed in the Circus Maximus. It was overthrown, broken into three pieces, and a piece was removed from its base before re-erecting. It weighs about 985,600 pounds. Its partner yet stands at Heliopolis. It is marked with the name of Osirtasen I., about 2100 B. C. Roman obelisks were also imported by Augustus and Caligula. Other obelisks are found at Constantinople, Paris, Arles, Florence, etc. The Egyptian obelisks are usually of granite, but there are two small ones in the British Museum made of basalt, and one at Philae of sandstone. The date of the Flaminian obelisk, which is covered with hieroglyphics, is supposed to be about 1600 B. C. The obelisk in Paris, erected in 1833, was brought from Luxor. It is 76 feet in hight. Of the needles of Cleopatra, so called, one is standing, 63 feet in hight, and the other is lying upon the ground. “The mode of raising an obelisk seems to have been by tilting it from an inclined plane into a pit, at the bottom of which the pedestal was placed to receive it. A roller of wood was fastened at each side to the end of the obelisk, which enabled it to run down the wall opposite to the inclined plane to its proper position.” — Wilkinson. For a full description of the mode of moving and re-erecting an Egyptian obelisk, see the quarto L'Obelisque de Luxor, Histoire de sa translation á Paris, Paris, 1839. See also Cresy's Cyclopedia, ed. of 1865, pp. 38, 40; also pp. 1013-17. 2. A reference-mark in printing (+); also called a dagger.Ob′ject-find′er.
（Optics.) A means of regis. tering the position of a microscopic object in a slide, so that it may be readily found in future. Maltwood's finder is a glass slide 3 × 1 1/4 inches with a scale occupying 1 square inch ruled into 2,500 squares. See “Beck on the microscope,” p. 67.
Ob′ject-glass.
（Optics.) The glass at that end of a telescope or microscope which is presented toward the object. The objective. By it an image of the object is formed, to be viewed by the eye-glass. In good instruments of either kind the object-glass is achromatic and composed of several lenses, one being of flint-glass and the other or others of crownglass. See achromatic-lens ; lens ; telescope ; eye-glass ; field-glass.
Ob-ject′ive.
（Optics.) That lens or combination of lenses in a microscope or telescope which brings the image of an object to a focus in order to be viewed through the eye-piece. The object-glass. Though acromatic lenses had been applied to telescopes by Dollond near the middle of the eighteenth century, yet in 1821, according to Biot, opticians regarded the construction of a good achromatic microscope as an impossibility. In 1827 Professor Amici of Modena exhibited in England and Paris a horizontal microscope whose object-glass, of large aperture, was composed of three superimposed lenses. A microscope constructed by Chevalier, on Amici's plan, was awarded a silver medal. The theory of the subject was about this time investigated by
