Magnetism
The agent or force in nature which gives rise to the phenomena of attraction, polarity, etc., exhibited by the loadstone, magnet, etc. A watch will become magnetized by too close proximity to a powerful magnetic field, such as is developed in a dynamo electro machine, for producing electric light, or by coming in contact with an ordinary magnet, as well as other sources of magnetic or electro-magnetic influences, and by these means all its steel parts become permanent magnets. Each piece of steel has then assumed definite polarity, so that if it is balanced on a point like a compass, it will, like the latter, indicate the direction of the earth's magnetic poles. The influence of these separate magnets, one on the other, and the influence of the earth's magnetism on the different parts, become very potent disturbers of time, keeping. Hairsprings, balances, and other small steel parts often become magnetized through being handled with magnetized tweezers or being placed near or in contact with other steel tools that have been magnetized. Mr. B. Frese exemplifies the influence of the separate magnets produced in a watch by its parts becoming magnetized as follows: if we take two compasses and place them side by side, so that the two bearing points of the needles will form a right angle to their direction, neither of them will show any variation from their natural position or the position they are compelled to take by the influence of the earth's magnetism; but by moving one a little to the North or South of this position, we notice a deflection in both, which is caused by the poles of unequal names having been brought near to each other. Besides this main disturbing influence upon accurate time keeping, we must also consider the disturbance caused by direct attraction, which takes place by two magnetized parts when their equal, as well as their unequal, polarities come close together, but when two extremities of equal polarity come close together or in contact, the stronger magnetized piece will cause the weaker to assume its own polarity, so that when the South polarity of a strongly magnetized piece is brought in contact with the South polarity of a weaker, the South of the latter will be changed to North, and the North to South when the two North polarities have been in contact. The largest steel parts in a watch are the mainspring and the case springs, and these are, therefore, the most potent to cause a disturbance in a steel or compensation balance, aside from the earth's magnetism; the balance being the medium by which nearly all the disturbance is caused, as during its vibrations it makes different positions to the polarities of the other steel parts, as well as the earth's polarities, which is the greatest disturber, aside from the mainspring, the polarities of which change in relation to the balance as the watch runs down. The force one magnetized piece exerts on the other multiplies with decreased distance. The fork, pallets and 'scape wheel are too small in bulk to cause much disturbance, either by direct attraction or directive force, unless they are charged to saturation, which very seldom occurs. If a magnetized balance is placed on a poising tool, with the staff in North and South direction, it will appear out of poise, caused by the earth's magnetism, and will maintain its North polarity uppermost. If it is placed in an East direction, it will no longer allow the North polarity to remain uppermost, but will cause the same to move toward the North and indicate the magnetic dip, the amount of which varies in the different latitudes of the globe. If we place the balance in a horizontal position, its north and South polarities will coincide with those of a compass, showing that if the balance were the only part magnetized in a watch, that magnetism caused more complicated variations than a balance out of poise to the same extent. That trying to poise a magnetized balance would be useless, is self-evident, for the reason that in a horizontal and North and South position, no equilibrum can be obtained. The influence of magnetized parts that do change position in a watch, is a constant one, as long as the size of vibration is maintained, and is, therefore, not the cause of serious disturbance. The substituting of new case springs will, therefore, be of little or no benefit.
To detect magnetism, place a pocket compass upon a show case, and place the watch to be operated upon on the table and close to the compass, and to the East and West of it. Before starting the test, stop the watch, and keep it from running by inserting a wedge made from a thin slip of paper beneath the balance. Turn the compass box around until the needle points to zero, before approaching the watch to it. Having placed the watch to the East or West of the compass, proceed to turn the movement, presenting first one figure of the dial and then another to the compass, and at the same time noting the deflection of the compass needle. Note whether the deflection is towards the East or West, i.e., whether it repels or attracts the needle. If the movement is not magnetized, the compass needle will remain stationary. If it is magnetized, the needle will be deflected, and by noting the spot, you can very readily detect the magnetized part. Magnetism may be removed from small steel parts by placing them in the lathe and revolving them rapidly, and at the same time approaching them with a horseshoe magnet, and then gradually withdrawing the magnet. It is not good policy, however, to place any magnetized piece in your lathe, as you are liable to magnetize chucks, and they will cause you no end of trouble in the future. Demagnetizers are now to be purchased so cheaply that it will scarcely pay you to experiment with home made substitutes. See Demagnetizer.