A huge wildfire in the Angeles National Forest last month consumed more than dozens of homes and timberland. The 38-thousand acre Williams fire also claimed one-thousand jars of dirt considered precious by scientists studying the effects of pollution on soil. The jars were part of a scientific experiment that began in 1935. They were stored inside a shed with concrete walls and a tile roof. Some jars were left intact after the fire. But others had identifying labels charred, rendering them useless.