Magnetical Investigations. 2pt (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1852 edition. Excerpt: ... those by which changes in the magnetic condition of ferruginous bodies are generally understood to be regulated. For the better guidance of the enquiring manipulator, I shall give the results of much personal investigation and experience in the form of directions, or experiments, commencing with a description of the simpler processes for neutralization, as adapted for all ordinary and general purposes in magnetic researches. 29. Demagnetizing Process.--Case I.--For neutralizing any incidentally-acquired polarity, in a, poker, or other bar or rod of iron. With a sensibly acting compass placed on a deviation-board, or, more roughly, on the surface of a table tolerably free from iron, --place the poker, or bar, to be demagnetized, in the direction of the east or west point of the compass, and a few inches distant from it, to ascertain, first of all, the nature and extent of its existing polarity. If it be a poker, the knob end being presented to the needle, will ordinarily attract the north pole, --the point, to be considered as the marked end, having northern polarity. If it be a plain bar of iron, let the end which indicates northern polarity be marked, or at least well observed. Holding now the poker or bar in the hand in a horizontal position, east and west, strike it a few blows, sharply or moderately, according to the quantity of the magnetic energy previously indicated, upon any part of its substance. Its magnetism will now be probably found to be considerably reduced. With the knob end of the poker (yet presumed to be a south pole) resting on the table near the compass, raise the other end, until the earth's inductive influence (acting conversely to the polarities of the bar) reduces the action of the bar to an apparently neutral condition;...