In 1,500 lectures during the last five decades, Professor Emeritus Albert Bartlett of the University of Colorado at Boulder physics department has warned of the perilous effects of population growth. On Nov. 15, he'll continue spreading the word. Bartlett's classic "Arithmetic, Population and Energy" lecture, part of the monthly Saturday Physics Series, will begin at 2 p.m. in Duane Physics room G1B20 on the CU-Boulder campus. It will be the 1,501st time he's given the talk.