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This Bio-Module requires the use of the text book "Exploring Life" by Professor John Blamire.
The common, mercury thermometer was invented by Gabriel Daniel Fahrenheit in 1714. He filled a very narrow, evacuated tube with mercury that expanded and moved up the tube when heated. The amount it moved up the tube was proportional to the temperature. Then he needed to set a scale.
To do this he first tried to create the lowest temperature then possible by mixing salt with ice in equal portions and noted where the mercury sank to in his thermometer when placed in this mixture. This he called zero. He then placed the thermometer under his wife's arm, watched the mercury expand and where it came to rest he called 100. (His wife must have had a fever that day!).
Between these two marks he carefully made 100 divisions called degrees. Fahrenheit's scale had 100 degrees (or steps) between his two set points, and we still use his scale today.
However, in 1742 Anders Celsius, a Swedish astronomer suggested two different set points for the thermometer; the freezing point and boiling point of pure water. Between these two points another 100 divisions or steps produced the Celsius scale. This is the scale used in science today. Since it has a hundred steps (or divisions) between its set points, it, like the original Fahrenheit scale is a centigrade scale, but it is common today only to use the term centigrade when talking about the scale devised by Celsius.