Having been requested to act on a Committee of the British Association, appointed to devise and apply methods for measuring the comparative intensity of earthquake shocks, and having been shewn several ingenious contrivances by Mr David Milne (who suggested the inquiry) Lord Greenock, and other persons, an apparatus occurred to me which should unite the requisites of Simplicity, Compactness, Comparability, and an easy adjustment of Sensibility according to circumstances.

Mr Milne had not failed to distinguish the ends for which instruments (which for obvious reasons were to be self-registering) ought to be devised, such as the measurement of horizontal concussions, of vertical elevation, and of heaving or angular motion of the surface. It is no part of my present object to consider the probable movements of the soil in earthquakes. I limit myself to the description of a single instrument intended to measure lateral shocks, such as are experienced by objects placed upon a table which is abruptly shoved forwards.