"Universal" Helio-chronometer, for Northern Hemisphere, 1901-1922
Universal Helio-chronometer, with rag-bolt, screwdriven box key, patent No 10,787, Pilkington and Gibbs Ltd., Preston,1901-1922. It was designed to correct for the equation of time, meaning that standard mean-time could be ascertained at any place, providing there is sunlight. This model for use in the Northern hemisphere, a serparate one designed for Southern hemisphere.