Mime, Wikipedia defies you
'The observation that old windows are often thicker at the bottom than at the top is often offered as supporting evidence for the view that glass flows over a matter of centuries. It is then assumed that the glass was once uniform, but has flowed to its new shape, which is a property of liquid. The likely source of this unfounded belief is that when panes of glass were commonly made by glassblowers, the technique used was to spin molten glass so as to create a round, mostly flat and even plate (the Crown glass process, described above). This plate was then cut to fit a window. The pieces were not, however, absolutely flat; the edges of the disk would be thicker because of centripetal force relaxation. When actually installed in a window frame, the glass would be placed thicker side down for the sake of stability and visual sparkle.[24] Occasionally such glass has been found thinner side down or on either side of the window's edge, as would be caused by carelessness at the time of installation.'

And Wikipedia is always right, otherwise I'd be failing my degree.
(Stu Moo winner of five nobble piece prizes, Fri 25 Jul 2008, 11:37, Reply)