What is "tasimeter"

n. An instrument for detecting or measuring minute extension or movements of solid bodies. It consists of a small rod or disk of carbon forming part of an electrical circuit, whose resistance (varied by the changes of pressure produced by the movements of the object to be measured) causes variations in the strength of the current, which are indicated by a sensitive galvanometer.

The tasimeter, or Microtasimeter, or measurer of infinitesimal pressure, is a device designed by Thomas Edison to measure infrared radiation. In 1878, Samuel Langley, Henry Draper, and other American scientists needed a highly sensitive instrument that could be used to measure minute temperature changes in heat emitted from the Sun’s corona during a solar eclipse, due to occur along the Rocky Mountains on the 29 July of that year. To satisfy those needs Edison devised a microtasimeter employing a carbon button.