Steel Ball Coherer.
A recent writer has recommended the use of balls of steel, such as are used in ball bearings, such, however, not to exceed ⅜ inch diameter. Such a coherer would take the form of an upright glass tube, with electrodes exerting pressure on a series of four or more steel balls. Decoherence here becomes difficult, and mention is but made of it to show the variety of forms which this important little article may assume.
Coherers are adjusted by advancing or receding the electrodes, altering the quantity of the filings, etc. There exists but little difficulty in operating coherers; considerable latitude is permissible as to adjustment, size, character, etc. There does not seem so much difficulty in obtaining sensitiveness as in guarding against external electrical disturbances. Wings or vanes of thin sheet metal are sometimes attached to the metal ends or electrodes of the coherer for purposes of adjustment, their size and capacity being determined by experiment. It is best that they present no sharp angles, but be of a disc, or spherical, form, the better not to dissipate energy.