Because mercury is so dense, a magnetic metal needle will float on it, and can be pushed against some friction (a magnetic back plate).
At maximum temperature the furthest needle will stay behind, attracted by the metal backing plate.
When such an extension can be seen, a thermometer can be made.
Just about all processes depend on temperature because heat makes molecules move or vibrate faster, resulting in faster chemical reactions. When substances are cold, the processes within proceed more slowly, as in chilled or frozen foods.
It does not surprise therefore that many ways have been invented to measure and control temperature.
We hope it will be of occasional use to radiocarbon users and interested students alike.
Copyright 1999 Tom Higham, Radiocarbon Laboratory, University of Waikato, New Zealand (Email: [email protected]).