> >> >>Instead of mercury, why not use some kind of metal plate on the bottom. It >>would probably by a lot less toxic, as well as cheaper. >> >> >That and other than cracking a TON of mercury switches, it's rather hard to >come by. > I should think that it is available readily from a chemical supply company. While it is heavily restricted these days for general manufacturing, there are processes that depend on it, and it is relatively cheap.