Do you like knowing things? About buildings? And have a couple free hours this afternoon? Today, University of Washington architecture professor Jeffrey Ochsner is giving a free talk on Seattle's buildings, beginning in 1880, when the city's total population was 3,500, through 1940. (Next Saturday is part two—1940 through 2010.) Having never been to a Seattle Architecture Foundation lecture, I can't vouch for it, but (1) did I mention it's free? and (2) if it's boring, you can always go up to the 10th floor and survey the city's architecture yourself. It's beautiful up there. (Microsoft Auditorium, Central Library, 1000 Fourth Ave, 386-4636. 1 pm, free.)