Clock

A clock from the Latin cloca, "bell" is an device for measuring time. A clock is generally a physical instrument, an especially accurate one is called a chronometer. The clock in its recent form 24 hour clock has been in use since at least the 14th century. Clock can refer to an conceptual system of time measurement ed. see calendar for other measurements.

Practically all computers depend on an exact internal clock signal to allow synchronized processing. (A few research projects are developing CPUs based on asynchronous circuits). Some computers also preserve time and date for all manner of operations whether these be for alarms, event initiation or just to display the time of day.

Watch

A watch is a little portable clock that displays the present time and occasionally the present day, date, month and year. In modern times they are generally worn on the wrist with a watch-strap, although before the 20th century most were pocket watches, which had covers and were carried separately, often in a pocket, and hooked to a watch chain. In previous times mechanical timepieces were used, powered by a spring wound regularly by the user. The creation of "Automatic" or "Self-Winding" watches allowed for a constant winding without special action from the wearer: it works by an eccentric weight, called a winding rotor, that rotates to the movement of the wearer's body. The back-and-forth movement of the winding rotor couples to a rachet to automatically wind the watch. Watches may be collectible; they are often made of precious metals, and can be considered an article of jewelry. Types of watch Pocket clock The first necessit for portability in time keeping was direction-finding and mapping in the 15th century. The latitude could be calculated by looking at the stars, but the only way a ship could measure its longitude was by comparing timezones; by comparing the midday time of the local longitude to a European meridian (usually Paris or Greenwich), a sailor could know how far he was from home. However, the procedure was notoriously unreliable until the introduction of John Harrison's chronometer. For that motivation, most maps from the 15th century to c.1800 have precise latitudes but distorted longitudes. The first logically accurate mechanical clocks measured time with weighted pendulums, which are useless at sea or in watches. The creation of a spring mechanism was crucial for portable clocks. In Tudor England, the development of "pocket-clockes" was enabled through the development of reliable springs and escapement mechanisms, which allowed clockmakers to compress a timekeeping device into a small, portable compartment It is rumoured that Henry VIII (the portrait of Henry VIII at this link shows the medallion thought to be the back of his watch) had a pocket clock which he reserved on a chain around his neck.

Wood Tree

Formation A tree increases in diameter by the formation, between the old wood and the inside bark, of new woody layers which envelop the entire stem, living branches, and roots. Where there are patent annual seasons, this can happen in clearly visible layers, known as expansion rings or annual rings, as can be seen on the end of a log; where there is no seasonal difference, the layers of new wood are uniform and not readily discernible. Within a enlargement ring it may be possible to see two more or less well-defined parts. The part bordering the centre of the tree is more open textured and almost invariably lighter in color than that near the outer portion of the ring. The inner portion is formed early in the season, when growth is moderately rapid; it is known as early wood or spring wood. The outer portion is the late wood or summer wood, being shaped in the summer. In white pines there is not much dissimilarity in the different parts of the ring, and as a result the wood is very consistent in texture and is easy to work. In hard pines, on the other hand, the late wood is extremely dense and is deep-colored, presenting a very decided contrast to the soft, straw-colored early wood.

Wood

Wood is the xylem handkerchief of woody plants, notably trees but also shrubs. Wood from the concluding is only produced in small sizes, reducing the diversity of uses. Wood is a hygroscopic, cellular and anisotropic objects . Dry wood is self-possessed of fibers of cellulose (40%–50%) and hemicellulose (20%–30%) held together by lignin (25%–30%). Artists can use wood to generate delicate sculptures.Wood has been used by man for millenia for many purposes, being many things to many people. One of its most important uses is as fuel. It may also be used as a substance, for making artworks, boats, buildings, furniture, ships, tools, weapons, etc. Wood has been an imperative construction material since humans began building shelters, and remains in plentiful use today. Construction wood is generally known as timber in International English, and lumber in American English. Wood may be out of order and be made into chipboard, engineered wood, hardboard, medium-density fibreboard, oriented strand board, paper or used to make other synthetic substances.