Description of a method of registering magnetic variations
Charles Brooke · Abstracts of the Papers Communicated to the Royal Society of London · 1851
Abstract A vertical stream of light issuing through a slit in the copper tube of a camphine lamp, is reflected by a concave mirror fixed vertically on the axis of a suspended magnet, and condensed into a focus by a cylindrical lens placed at the distance of about seven feet from the mirror. The luminous image, which shifts its position according to the movements of the magnet, but to a much greater extent, impinges on highly sensitive photographic paper, wound round a horizontal cylinder, which is made, by a watch movement, to revolve once in twelve hours. Thus, by a combination of the vertical movement of the paper with the horizontal movement of the image, the magnetic curve of variation is distinctly portrayed and registered.