La librairie des livres interdits

Marc Levy

Description

Gnomonics is to the scientific what the Art of Dyalling is to antiquaries: both refer to the art, science, and craft of sundials. The sundial, the oldest mechanical clock, is also the truest -- when properly set and corrected it is more accurate at its longitude than modern "standard" time clocks. For beneath and behind the shadows on the dial operate principles of celestial mechanics, geography, trigonometry, and magnetism. But can a sundial be built with this knowledge? Yes, in fact, with proper guidance, a good deal of sundial science can be learned in the making. Here is the guide. The book gently leads beginning diallists into sundial lore and construction. Novice craftsmen who can wield a saw, wood-burning pen, matte knife, sandpaper, and a few other simple tools can make five different kinds of sundials; plans are flexible and allow for embellishment, alteration, and variety of materials. Pre-calculated templates can be removed from the book and transferred by carbon paper to wood. Illustrated step-by-step instructions show how to build these sundials: Horizontal; Direct South Vertical; Folding Equatorial; Bowstring Equatorial; and Diptych. Ultimately, one can design a working pocket sundial! Tables are included for four different latitudes (25°, 32°, 40°, 45°), applicable throughout the United States and much of North America. A table of more than one hundred cities gives latitude, longitude, time, zone, magnetic variation, and the necessary time adjustments. A special section is given to dial correction; the equation of time, longitude, magnetic variation, hour angles. A bibliography and a list of sundial mottoes complete this comprehensive beginning manual.

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