The description and use of the universall quadrat.: By which is performed, with great expedition, the whole doctrine of triangles, both plain and sphericall, two severall wayes with ease and exactness. Also the resolution of such propositions as are most usefull in astronomie, navigation, and dialling. By which is also performed the proportioning of lines and superficies: the measuring of all manner of land, board, glasse; timber, stone. &c. / By Thomas Stirrup, Philomathemat.

CHAP. IV. The Height of the Sun being given, to finde the length of the contrary shadow.

BY the contrary shadow is understood the length of a∣ny shadow that is made by a Staffe or Gnomon, standing at right angles against any perpendicular wall, in such a manner that it may lie parallel to the Horizon; the length of the contrary shadow doth increase as the Sun riseth in height; whereas the right shadow doth de∣crease in length, as the Sun doth increase in height.

Wherefore to finde the length of the vers∣ed shadow, place the threed upon the height of the Sun given in the Quadrant, and it will cut the contrary paral∣lel of the Gnomon, at the right parallel of the shadow.

[illustration] diagram of the measurement of length of the sun's shadow

Let AB be a perpen∣dicular wall, AC a Gnomon making right angles there with, the length whereof is 60, and the Suns Altitude 53 deg. 8 min. the an∣gle ACD; now if you place the threed at 53

deg. 8 min. in the quadrant, it will cut the contrary paral∣lel of 60, at the right parallel of 80, and such is the length of the contrary shadow AD which was required.