Fig. 134. Globe Gores of Henricus Glareanus, 1527.
Dürer had proposed the employment of sixteen segments, Waldseemüller, Schöner, Boulengier, and Glareanus had thought twelve a more suitable number. As the years passed we find a preference manifesting itself now for twelve, now for sixteen, now for eighteen, twenty-four, or thirty-six with a more common preference for the smaller number. The several biangles for the maps alluded to above were fashioned to extend from pole to pole in what we may call the equatorial system; Mercator, as has been noted, introduced the novel idea of truncating his gores twenty degrees from each pole, preparing as a covering for the remaining polar space a circular disc, having the required diameter of forty degrees.[198] This plan he proposed for the practical reason that a paper covering for a sphere so constructed could be applied with greater ease and with greater accuracy than one consisting of complete biangular figures, remembering the tendency of the paper to expand and the difficulty in avoiding folds.
As there was much inclination among map makers to experiment in the matter of map projection so there was an inclination to experiment, as the years passed, in the matter of design for the globe gores. In the so-called Da Vinci gores we find them drawn in two groups of four each (Fig. [135]), and instead of the globe biangle we have the globe equilateral triangle. Their application to a spherical surface could only have been made with difficulty, if at all; indeed we cannot be certain that in so outlining a map of the world the draughtsman’s intention was to use it in globe construction. The plan seems never to have been followed by any of the other map makers, or by any globe maker. We find an interesting early instance in which the gore map construction was clearly employed merely as a method for plane map making, a method having certain very commendable features (Fig. [136]). The author of this map is unknown.
Fig. 135. Gore Map of Leonardo da Vinci, ca. 1515.
