Scientific American always has a 'Working Knowledge' section in each edition dealing with various practical technologies. In the September edition that I have mentioned previously the title is 'Tall Task', and it is on water towers and their role in the water supply system of towns and cities. What I find odd is the mention of rooftop water towers in cities. To be honest I've never seen such things in prairie cities. But now I am on the lookout for them here in Winnipeg. If they aren't there why ? Are they an affectation of American rather than Canadian cities ? Are they unnecessary in prairie cities ? A question to ponder.