Methods for Measuring the Height of a Tower

The image is divided into two horizontal registers, each featuring a cylindrical tower set in a landscape. In the top register, a mirror is placed on the ground, creating a geometric reflection that allows for the calculation of height via similar triangles; lines indicating the visual path are drawn between the mirror, the tower, and a ghosted image of the tower. In the bottom register, a man standing on the left holds a quadrant, sighting the top of the tower through the device’s aperture to determine the angle of elevation. Both registers use numbered annotations (6, 16, 18) to denote distance and height dimensions, with fine hatching used to provide depth to the hills and the masonry of the towers.

This illustration reflects the 17th-century focus on applied mathematics and surveying techniques as foundational to early modern natural philosophy. It serves as a visual guide for the practical implementation of trigonometry, which was essential for architecture, cartography, and military engineering.