[BITList] Trickle-down effect

[HUGH]

John,

I can't find my sources, so I speak from memory.  I wrote an essay for the 
OU on public health in early Victorian times, drawing on local sources, and 
I came across what I believe was Simpson's sand bed filter, the earliest 
recorded of that type.  However, I got some brownie points for finding an 
earlier filter of the same type, developed by Robert Thom in Greenock to 
produce clear water for the mills on the Shaw's Water Works, early 1820s. 
It is ironic that, while the sheets were being kept white, the population of 
the town below were dying from polluted water.

Hugh.