A depiction, in the form of a revolving sphere mounted at the poles, of the earth or the constellations of the heavens. They are known as terrestrial (earth) and celestial (heavens) globes. Although often designed as furniture for libraries, there is some evidence that they were used, especially during the 16th century, as instruments of navigation, although it seems very doubtful that they were put to practical use at sea. In the days before logarithms and the principle of the true Mercator projection, the problems of nautical astronomy could be solved only by prolix mathematics which, in general, were foreign to navigators. Globes, however, offered the means of demonstrating many of the problems instrumentally by inspection. Finding the latitude from two altitude observations of the sun or a pair of stars, finding the true azimuth of a heavenly body, or finding the rhumb line course and distance from one position to another were problems easily solved with a celestial or terrestrial globe.
An important treatise on the use of globes, including navigation, was written by Robert Hues and published in Latin in 1592. It was ‘made English for the benefit of the Unlearned’ by Edmund Chilmead in 1638. In the eyes of the original author, the most important part of the treatise was that dealing with the practical uses to which globes could be put by the navigator.
With the advent of the Mercator chart and arithmetical navigation, facilitated by the use of logarithms, the fragile, cumbersome, and costly globes fell into disuse so far as ship navigation was concerned.
Subjects: Maritime History — Early Modern History (1500 to 1700).