Mass Production of Watches

Time of Manufacture.

Taking another example to give a more concrete conception of rapidity with which operations are performed, the following outline, covering nearly all the steps in the making of "a mass production watch," gives the equivalent time of manufacture of one individual watch in seconds: The back plate, involving 17 operations by 25 hands for 103 seconds; front plate, 12 operations by 7 hands, 29; barrel, 1 o op erations, boring, levelling, turning, sizing, punching hook for spring, assembling spring, fitting arbor and testing, 69 ; centre pinion pivoted, 29; other pinions pivoted, each 40; wheels stamped, 0.3 ; staking centre wheel on pinion, 4; staking third and fourth wheels on pinion, each 7; fitting centre arbor, 4; staking escape wheel on pinion, 7; making brass screws, 1.25; mak ing steel screws, 2.5; making winding stem, 15; grinding balance staff, 3.6; fitting balance and pinning hairspring, 51.4; drilling for impulse pin, 4.1; staking impulse pin, Putting in balance staff, 4.8 ; truing wheel in press, 4.1; lining up, 4.5; putting on roller, 5.5; general inspection, 4; spinning, 4.3; poising balance, 18.9; assembling movement, 72; washing movement, 4; oiling train parts, 20.5; fitting stem and winding wheel, winding with lever not in, 4; lever put in, inspection for end shake and winding, 45 ; putting on hairspring, 4.5; truing hairspring, 17; vibrating hairspring, 91.1; setting balance to beat, 7-2; putting hour hand on hour wheel, 2.4; putting on dial and hour wheel, 17; putting on minute and seconds hands, 17; putting in case, shaping hands, driving three screws and putting on tern porary back, 117; oiling and winding, 42.3; timing, comprising four 24 hour runs with dial down for interference of hands, pendant up with two-minute tolerance and another run with permanent back and bezel on, 17o; putting on permanent back and bezel, 14.4; inspection and packing, 18.2. The making of the case involves 16 operations, ranging from four-tenths seconds to nine and seven-tenths seconds; total, 36 seconds.

(P. M. C.) WATER, considered chemically, is an oxide of hydrogen hav ing the composition H,0 (see below), but naturally occurring waters all contain impurities in varying degrees. Most water is derived directly or indirectly from the ocean by evaporation, con densation in clouds and precipitation, as, for instance, in the form of rain, after which, it reappears in rivers, springs, lakes, etc. In evaporation the salts contained in the ocean are left behind, and rain water is therefore free from these ; but it acquires traces of ammonium salts and various gases from the air, and traces of sulphuric acid derived from the burning of sulphur in coal, in the neighbourhood of towns. Lake waters are relatively pure, espe cially in mountainous districts where pollution from animal, agri cultural or industrial sources is minimised, but they may contain considerable quantities of suspended mineral or peaty matter. River waters acquire a variety of impurities from soils which they traverse, from drainage of fields, and from factory and sewage effluents, and shallow well waters are frequently vitiated from the first two of these causes. Spring waters and deep well

waters have usually undergone a prolonged process of filtration which tends to clarify them from suspended matter, and to purify them from dangerous contamination, but at the same time they acquire considerable quantities of dissolved salts.

The nitrogenous organic matter in waters is a useful indication of contamination. Certain bacteria break down this material into ammonia, which is slowly oxidised to nitrites and nitrates by other bacteria. By Wanklyn's method of water analysis it is possible to find, (I) the amount of "free or saline" ammonia, and (2) the amount of "albuminoid" ammonia, which is a rough index of the organic matter still undecomposed. Although the free ammonia itself is harmless, it is an almost certain indication of former pollution. A consideration of these two quantities, in conjunction with the source and history of the water, is of great value in determining its suitability for human consumption. So many factors are involved that it is useless to give definite figures, but it may be said that if either type of ammonia (and especially the second) exceeds 0.005 parts per 1oo,0oo, the water is open to suspicion, and if they exceed 0.010 parts, it is probably danger ous. Further, the presence of nitrites in water is an almost cer tain indication of recent sewage contamination, otherwise nitrates and not nitrites would be found. Prolonged aeration tends to de stroy the organic matter on which harmful bacteria thrive, and boiling almost invariably renders waters safe for consumption.

The saline constituents of a water have some effect on its potability but are more important in connection with industry. The dissolved salts are largely those of calcium and magnesium, which are retained in solution owing to the presence of carbon dioxide (see CALCIUM). These salts cause "hardness," i.e., they hinder the lathering of soap. When hard water is boiled, the car bon dioxide is expelled, and calcium carbonate is deposited as a "fur" or boiler crust ; the hardness due to this cause is therefore called "temporary," whereas that due to other salts (magnesium and calcium chlorides and sulphates) which are not thus deposited is called "permanent." In determining "hardness" successive small quantities of a standard soap solution are added to a known volume of water in a bottle which is shaken after each addition. After a time a lather forms which has only a transitory existence, but at a certain stage it will persist for some minutes. The volume of soap solution necessary to secure this condition is noted, and the hardness can then be calculated. The soap solution is usually standardised to give hardness as parts of calcium carbonate per 100,000 parts of water, or sometimes (as in Clark's solution) in grains per gallon (I part in 70,00o). Roughly, it may be said that a "hard" water shows more than 15 parts (or degrees) and a "soft" water less than 5 degrees.