Timothy O'Donnell, age 14, of Lakewood, Ohio, for his question:

What unit is the metric system based upon?

Someday soon we hope to change our bungling weights and measures to the metric system. This neat, time saving system is based on decimals, or multiples of 10. Its units of weight and volume, area and capacity are related to each other and all are figured from the meter    the basic unit of length. When you know the length of a meter, you can figure out all the other measuring units in multiples of 10.

Measured against our out moded yard, the meter is roughly 39.37 inches.. This, of course, is not nearly precise enough to satisfy the weights and measures experts. Until 1960, the standard meter was a delicately tailored bar of platinum iridium alloy. A more precise figure was reached by the spectrograph. Since 1960, the standard meter has been equal to 1,650,763.73 wavelengths    as figured from the orange red light of the isotope krypton 86. One meter equals 10 decimeters. One cubic decimeter of water is a litre and one litre weighs a kilogram.