41. It further uses the armillary sphere and details rules relating to problems of trigonometry and the computation of eclipses. 42. A large iron armillary sphere stands in the center of the square, supported by six small metal turtles. 43. Crowning the top of the clock tower was the large bronze, mechanically-driven, rotating armillary sphere. 44. Many, especially larger building, also had arches and towers topped with nationalistic symbols such as armillary spheres. 45. This was used alongside a clepsydra clock and waterwheel to power a rotating armillary sphere in representation of astronomical observation. 46. The armillary sphere is also featured in Portuguese heraldry, associated with the Portuguese discoveries during the Age of Exploration. 47. A similar flag was introduced for the Portuguese ships that sailed to India, but with a red armillary sphere. 48. No early Islamic armillary spheres survive, but several treatises on " the instrument with the rings " were written. 49. The armillary sphere was granted by King Viseu as his personal badge when he was appointed heir of the Crown. 50. It may be considered to be a simplified, portable armillary sphere, or a more complex form of astrolabe.
