Lawyer Harry S. Wender was walking through the lobby of the Commerce Department when his eye fell upon the "population clock on display there. The nation's population was given as something more than 300 million he was surprised to note.

The Bureau of the Census supplies the data for the display, so I called Ray Bancroft at Census headquarters in Suitland and asked him what the numbers were supposed to be.

"You're writing for Thursday morning?" he asked. "Let me look at my estimates for July. Here we are. At 8 a.m. on Thursday, the clock should begin with 217,325,675. We merely supply the figures. A man at Commerce checks the clock every morning and makes whatever adjustments are necessary when the mechanism gets out of kilter, as any mechanical or electrical device will from time to time." "How do you determine what the figure is supposed to be for a given day? I asked.

"Inasmuch as we take a complete census only once in 10 years," Ray explained, "the daily figure is an estimate - but a very good one. We base it on the frequency of births, deaths, immigration and emigration."

What are those frequencies? I inquired.

"There is a birth every 10 seconds and a death every 16 seconds," Ray told me. "A immigrant arrives in our country every 81 seconds, and a resident emigrates every 15 minutes."

My cordless abacus indicates that our population is now growing by more than 6,000 a day, or almmost 7 million a year.