This section is from "The American Cyclopaedia", by George Ripley And Charles A. Dana. Also available from Amazon: The New American Cyclopędia. 16 volumes complete..
William Gascoygne, the inventor of the micrometer, born in England about 1621, killed fighting for Charles I. at Marston Moor, July 2,1644. The instrument, as constructed by him, consisted principally of two parallel wires or metallic plates, capable of being moved, which were placed in the focus of the eye glass of the telescope. The image was comprehended between these, and by means of a scale for the measure of angles its diameter was determined. Gascoygne used his instrument in various astronomical observations, and in determining the magnitude or distance of terrestrial objects.