Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/424

Rh 398 W A T W A T 12. and consequently the watch will go longer without cleaning ; and it also saves the thickness and the cost of a double back to the case. The first plan of the kind was that of pulling out the knob of the handle, which went into the watch, and had a gathering click attached to it which wound up the fusee, or the barrel, by means of a ratchet. But this was not found to answer : it was liable to get out of order ; and, moreover, at every time of winding fresh air was pumped into the watch, which soon produced injurious effects. A far better plan is that of combining the two objects of winding and setting the hands by means of the handle, in the manner we shall now describe. In fig. 12 d is a wheel on the barrel, with bevelled teeth, and there is an other small bevelled wheel on a spindle b, which ends in a milled head a, within the handle or pendant ; these two wheels cannot conveniently be arranged so as to work into each other without the inter vention of a third between them, which is marked e in the left-hand section. It is easy to see that turn ing the milled head will wind up the barrel. The same arrangement might of course be applied to the fusee, though it would increase the size ; but in fact these watches are made without one, and the practice is increasing. The winding wheel d is also made with the well-known contrivance of Breguet, known by the name of the &quot; tipsy key &quot; when applied to a common winding key, which enables you to turn the handle the wrong way without doing anything except moving a ratchet-wheel over its click, and consequently without straining the watch in attempting to wind it the wrong way. The same handle and wheels are also made use of to set the hands, thus : there is a small wheel /which turns on a stud at the end of the lever fgh, and as the lever turns on a pivot at g, when its end h, which just projects through the rim of the watch, is pushed on one side, the wheel /will then be thrown into gear with the winding wheel d and the hour pinion in the middle of the watch ; and consequently, if the handle is then turned, it will alter the hands, just as they are usually altered from the back by a key in foreign watches, so that the face need never be opened. Of course, while this is doing, you do at the same time wind up the watch a little if the hand has to be turned the way for winding ; but that is of no consequence, except that you cannot put the hands forward immediately after you have completely wound up the watch. There are various other arrangements for winding and setting by the handle substantially on the same principle. The ring is difficult to fix firmly when flexible on a stud perforated for the winding arbor, as no screw can go through it. The ring and the stud should be made in one piece. There is no use in it being hinged, as usual. In the chronograph watch there is, in addition to the centre seconds-hand, an independent seconds-hand which, when not in operation, stands at zero. Pressure on the crown-piece acts succes sively (1) on a starting motion, (2) on a stopping motion, and (3) on a motion which sends the hand back by the shortest path to zero. Watches are also made with what are called split seco?u?-hands, the two hands being in their ordinary state together and appear ing as one, but when you push in a knob one of them is stopped, while the other goes on ; the time shown by the stopped one is of course the time of the observation. Sometimes this is done by merely connecting the hands by a very slight spiral spring, which will allow itself to be untwisted one or two coils without stopping the watch ; and, as it cannot be of any use to stop the seconds- hand longer than a minute, this seems to answer. There is, how ever, another plan, in which these two hands, or at least the socket of one and the arbor of the other, are connected by a pair of disks set obliquely on the arbor and the socket respectively, so that, whenever the spring which keeps them together is allowed to act, it brings the loose hand up to the hand fixed on the arbor ; and it does not signify how long it may be stopped by throwing the disks out of contact. One of the disks is heart-shaped, and is connected with the other by a spring, forming what is called a. jumper. For the use of electrical engineers and others who are brought within the influence of powerful electrical machinery, it has been found necessary to introduce non-magnetizable watches. At present this is best secured by making the balance of silver or platinum alloy, and the balance spring of gold or palladium. The use of steel in moving parts of the works is carefully avoided, and thus fairly good timekeepers indifferent to magnetic influences are pro duced. The introduction of machinery for the manufacture of watch movements has had the effect of greatly cheapening the commoner class of watches, and yet supplying a fairly satisfactory timekeeper. It is in America that the application of machinery to watchmaking has found its greatest development, and its success has enabled the American manufacturers to obtain considerable foothold in the European market for cheap watches. But watch movements are also now very extensively made by machinery in Birmingham, Coventry, and several Lancashire towns. Under the auspices of the Koyal Society a department has been established at Kew observatory for the testing and certifying of watches in respect of their compensation for variations of tempera ture, and their uniformity of motion in different positions. Watches which obtain certificates of the first class have also awarded to them merit marks up to 40 for complete absence of variation in daily rate, 40 for absolute freedom from change of rate in different positions, and 20 for perfect compensation for variations of temperature. The testing establishment has only been insti tuted for a few years ; but its services are being largely sought by manufacturers of the high class of watches, who have laboured with equal zeal and success to keep the English-made watch un- approached by the product of any other nation. (0-.) WATER, 1 as everybody knows, is a generic term which includes a great variety of different substances. But when we compare any two species we always find more of agreement than of difference in properties which suggest that air waters consist essentially of the same thing, which is only modified differently in the several varieties by the nature or proportion of impurities. This surmise is confirmed by the results of scientific inquiry. In all ordinary waters, such as are used for primary purposes, the impurities amount to very little by weight- as a rule to less than y^tli of 1 per cent. Of all natural stores of water the ocean is by far the most abundant, and from it all other water may be said to be derived. From the surface of the ocean a continuous stream of vapour is rising up into the atmosphere to be recondensed in colder regions and precipitated as rain, snow, or sleet, &c. Some -j- 8 T ths of these precipitates of course return directly to the ocean ; the rest, falling on laud, collects into pools, lakes, rivers, etc., or else penetrates into the earth, perhaps to come to light again, or to be brought to light, as springs or wells. As all the saline components of the ocean are non volatile, rain-water, in its natural state, can be con taminated only with atmospheric gases oxygen, nitrogen, and carbonic acid. So we should presume, and so it is, except that these gases, having different rates of solubility, are not associated in rain-water (or natural water generally) in the proportions characteristic of their source. Thus, for instance, while atmospheric air contains 21 per cent. by volume of oxygen, a solution of air in water contains about 34 - per cent, of that gas. Besides, rain-water, for the reason stated, contains perceptible traces of ammonia, combined as a rule, at least partly, with nitric acid, which latter is being produced wherever an electric discharge per vades the atmosphere. This electrically-produced nitrate of ammonia forms no doubt the primary source of all organic nitrogen. Lake waters, as a class, are relatively pure, especially so if the mountain slopes over which the rain collects into a lake are relatively free of soluble components. As an example we may refer to the water of Loch Katrine (Scotland), which is almost chemically pure, apart from small, but perceptible, traces of richly carboniferous matter taken up from the peat of the surrounding hills, which impart to it a faint brownish hue, while really pure water is blue. River water varies very much in composition even in the same bed, as a river in the course of its journey towards the ocean passes from one kind of earth to others ; while, compared with spring-waters, relatively poor in dissolved salts, rivers are liable to be contaminated with more or less of suspended matter. Spring waters, having been filtered through more or 1 Compare CHEMISTRY, vol. v. pp. 483-485, and SEA WATER.