I've been at my new spot on the river for a couple of months now, and it's not all that far from my old spot. You'd think I'd know the New Jersey skyline pretty well. But every now and then I see a building I never noticed before. The light keeps changing in such subtle ways, different colors, different densities of mist and fog, different locations and heights of clouds, and suddenly it's as though a building has been just built or the one in front of it torn down. Today it was a red brick industrial structure from the twenties or thirties, the kind with strips of steel-framed windows and a tall water tank on one end of the roof.

And about those water tanks, in the informational portion of today's blog (an out-of-town friend asked me about this the other day): what they're for is the sprinkler system, not the building's general water supply. (WL, correct me if I screw any of this up.) Depending on the water pressure in the street, buildings over certain heights -- it tends to equate to five or six stories in most parts of NY -- need pumps to get water to the upper floors. In a fire you can lose electricity, and then your pump doesn't work. The water tanks hold enough water to fill the sprinkler system by gravity for a prescribed amount of time (there's a formula) so the building can have its sprinklers without electricity until the fire department arrives. You'll notice that tanks are at all different levels above the roofs, on taller or shorter steel structures. This is because the force needed to get the water into the system depends on the height of the tank above the highest sprinkler heads. So their location, which you can't tell from where the roof is, determines the height of the tank.

Thank you for your participation. We now return to our regular unscientific blogging.