Lesson 15-The riddle of time .evelopment of Clocks--Sun Clocks Another Egyptian shadow clock or sundial, possibly the first portable timepiece, came into use around 1500 BC. This device divided a sunlit day into 10 parts plus two"twilight hours"in the omit morning and evening. When the long stem with 5 variably spaced marks was oriented east and west in the morning, an elevated crossbar on the east end cast a moving shadow over the marks At noon the device was turned in the opposllo direction to measure the afternoon hours W BT E To be continued on the next page.Lesson 15—The Riddle of Time W B T L E Another Egyptian shadow clock or sundial, possibly the first portable timepiece, came into use around 1500 BC. This device divided a sunlit day into 10 parts plus two “twilight hours” in the morning and evening. When the long stem with 5 variably spaced marks was oriented east and west in the morning, an elevated crossbar on the east end cast a moving shadow over the marks. At noon, the device was turned in the opposite direction to measure the afternoon “hours”. To be continued on the next page. I. Development of Clocks—Sun Clocks