take the place of a pendulum, which of course can not be used in a watch. The next step was the invention of the lever escapement about 1770, which applies the regulation of the balance-wheel with much more accuracy than had been attainable. The fifth important step was the invention of the compensating balance. Watches are more affected by changes in temperature than are clocks, and it was necessary so to arrange different metals in the balance that the contraction or expansion of one would offset that of the other. This invention (1764) made possible the exactness of the chronometer, which in turn enables sailors to tell their longitude with precision. Perhaps the invention of stem-winding and stem-setting to take the place of the key so easily lost deserves the sixth place. The latest development is the application of machinery to the manufacture of watches, and this was brought about by American ingenuity about 1854, when the celebrated factories at Waltham (q.v.) were established. Not only does machinery make the parts more exactly than hand-labor, but this exactness makes it possible to dispense with the fusee and chain. The American watch has about 153 parts to the 800 parts that had to be brought together in the British or the Swiss watch. Improved methods of hardening steel made jewel-bearings less important, and so the way was prepared for the "dollar watch." Before machinery was applied, the parts of any one watch had to be specially made for it; but now the parts of a watch never face each other till they are ready to go into the case together. Being made of standard sizes, they always fit. Watch manufactories are now scattered over the north of the United States, but the chief centers are in Massachusetts, Connecticut, New York and Illinois. England and Switzerland make the better, Germany the cheaper, watches.
Wa′ter (H2O) is a clear, transparent liquid, formed of oxygen and hydrogen. It is almost colorless, though in large masses it looks blue. It freezes at 32°F. and boils at 212°F., and passes off in steam. Water dissolves almost everything it comes in contact with, so that strictly pure water is never found. Rainwater is the purest form, but even that has absorbed air and ammonia. Water is found very widely distributed in nature in the form of ice and snow, in watery vapor in the air, in lakes, rivers and seas, in the soil and rocks, in the sap and juices of plants and in the blood and flesh of animals. It covers three fourths of the surface of the earth, and forms a large part of the bodies of animals. The ocean is nature's great reservoir or cistern, and from it all other water may be said to be taken. A constant stream of vapor passes into the atmosphere and is condensed in colder regions, returning to the earth in the form of rain, dew, frost and snow, which fertilize the earth, are collected into pools, springs, lakes and rivers, and finally find their way back to the ocean. These waters all take up various substances, as is seen by the color of different rivers, which varies as the soil through which they pass. The water of the ocean is salt, but the saline or salty matter does not form a vapor, and so is left behind when the watery vapor rises from its surface. Besides its use in watering the earth and in feeding animal and vegetable life, water has been the great agent in forming the surface of the earth. A river carries with it a large amount of earthy matter, of which it has robbed the hills in which it springs, and deposits it in the valleys through which it flows; the great bars and deltas at the mouths of rivers being examples of the amount of land sometimes formed by the sediment in a river. This double process of breaking down and dissolving the rocks and of depositing and building up the land is constantly going on, and has been going on for ages. Geology gives the results of this constant action of water in past ages, as seen in the strata or layers of rocks which form the earth. In the form of ice or glaciers water has also had a large part to play in forming the continents. Some of the many purposes it serves are its use in supplying a motive-power to machinery, either mechanically, as in waterfalls, or by its expansion into steam, its use in cleansing and cooking or domestic purposes, its use in the laboratory as a solvent or dis-solver of most substances and its universal use by men, animals and plants for drinking purposes. Consult Tyndall's Forms of Water. See Glaciers, Ice, Ocean, Sea, Waterfall and Waterworks.
Water, Ascent of (in plants). Water to supply the evaporation from the larger land-plants enters by the roots, especially the root-hairs, and passes thence into the woody strands which lie in the center of the root. These connect with similar strands in the stem, which run into the leaves and branch profusely, following the so-called veins and constituting the veinlets. The water travels chiefly in the interior of the minute, elongated tubes (ducts or vessels) which make up the greater part of these strands. These ducts are not continuous tubes, however, so that the water has to traverse the partition walls which occur here and there (abundantly in pines and their kin). The water is not forced up from below by the roots, except in low plants and at some seasons; it certainly does not rise by capillarity. No satisfactory understanding of the forces concerned has yet been reached, though the problem has been attacked by many investigators. See Root-Pressure, Transpiration and Vascular Bundles.
