Rainy-day fun

摘要

I live in Seattle, where the rain drizzles steadily all winter. Heck, it rains all year. Because I work indoors, the weather usually causes me little concern. However, yesterday I encountered a big puddle in the parking lot outside my office. The puddle was large, brown, and uniformly 1/2 in. deep, with a sheet resistivity, ρ, of about 1200Ω per square. (Yes, I measured it.)