Is Glass a Liquid?

During dinner with friends recently I mentioned a fallacy I was told in high school by one of my science teachers. "If you can see through a substance it must be a liquid." This was used to justify the statement that glass was a liquid, which I did believe for many years.

One of my friends said he thought that the "glass is a liquid" statement was also false. The next day a flurry of e-mails and google searches turned up the "truth." The idea that glass is liquid appears to be a myth nearly unique to "english speakers of North America." See the wikipedia entry on glass and a page created to show that "Glass is a Liquid" is an Urban Legend.