You've got a valid point, Warren. I think it might be possible to get a pure compressive dome, but the base might have to be infinite. I think that there may be a solution that looks something roughly like a Gaussian revolved around the y axis. Basically, the "skirt" of the Gaussian pushes out on an ever increasing radius. You could cut off the Gaussian at some point beyond the "circle of inflection" and put a ring around it, but the tension in the ring falls to zero as the radius of the ring increases. At 08:19 AM 11/12/2012, Warren Smith wrote:

--well, now you've blown it. Your stated goal was to get pure compression. But as you just admitted, there is horizontal tension. But in your defense, I claim this is impossible to avoid, at least for a convex dome that eventually has vertical tangent; you unavoidably get compression along vertical "meridians" but tension along "lines of latitude."