Clocks Tell the Time by Alma Kehoe Reck

Man has always found a great need for measuring time. This book begins with very early time-keeping, and goes through water-clocks, sundials and early clocks to modern ones. At the end is the Atomichron, which may be the accurate time-keeper that will go with rockets into space.

Early mechanical clocks were worked by heavy weights, and had only an hour hand, as seen in the old clockmaker’s shop used on page 4. At that time people did not feel the need to know the exact time, nor had they made a clock accurate enough to tell it. In this age of science, time must be measured exactly. The Atomichron should lose only one second in three thousand years.