below the fold, for months, Dr Bill has been making interesting post.. one site he found was
engines of ingenuity.. transcrips of a 15 minute or so radio broadcasts.
http://www.uh.edu/engines/engines.htm

one episode was about Marie the Jewess, and her work with what we now call double boilers.
http://www.uh.edu/engines/epi964.htm

double boilers allow you to regulate heat.

in a water bath/water based double boiler, water, which boils at 212(f) or 100(c) controls the heat of the upper vessel (which is why we heat melt chocolte on a double boiler) --it keeps its (provided the upper and lower vessels aren't tightly sealed and there is escaping steam) at the upper bowl at the tempurture of boiling water..
(so the chocate or custard or what ever, never gets hotter than 100(c).

if you want to learn the melting point of an unknow material, being able to figure out if it is higher or lower than water is one step.
interesting how almost nothing is know about her.. (so true for so many woman in science.)


my other obsession