... "3-D" A SIMPLE TELESCOPE FOR BEGINNERS their experiments, these projects invite excursions across the bound-aries of many scientific disciplines including optics, mechanics, electronics, ... that imparts color to soap bubbles and blueness to the bluebird. 6. A PIEZOELECTRIC CLOCK 532 The accuracy of electric clocks depends on the care with which the operator at the power station ... the tool. Hence the center of the mirror and edge of the tool grind fastest, the mirror becoming concave and the tool convex. As grinding proceeds, the worker periodi-cally turns the tool slightly...