Today I found myself at a street-market in Soho (the one in London), at a stall belonging to Amelia Parker, a jewelry maker who salvages fragments of century-old clay pipes from the banks of the Thames. Clay pipes were once the equivalent of cigarettes, cheap, semi-disposable tobacco-distribution systems, and as they were very brittle, they were tossed out by the tens of thousands, forming a lightweight layer of river detritus that still washes up on the riverbanks in London.