&91;&46;&46;&46;&93;up some old records putting it back to Hoang-ti 2679 B&46;C&46;, but it appears to have been certainly in use in China in 1100 B&46;C&46;, so we will be satisfied with that date&46; In presenting a subject to the young student it is sometimes advisable to use round numbers to give a simple comprehension and then leave him to find the overlapping of dates and methods as he advances&46; Keeping this in mind, the following table may be to give an elementary hint of the three great steps in time measuring: Shadow time, 2000 to 1000 B&46; C&46; Dials and Water Clocks, 1000 B&46; C&46; to 1000 A&46; D&46; Clocks and watches, 1000 to 2000 A&46; D&46; I have pushed the gear 9781507566152