1.3 TEMPERATURE 13
scientific and applied measurements, and in particular the importance of purpose and
accepted measurement protocol in the design of applied measurements.
1.3.1 The evolution of the temperature scale
The very first record of a temperature scale belongs to the Greek Galen (AD 130–200)
who identified eight degrees of temperamentum, which he used to characterise the
temperament of his patients and the effects of his medicines. He also defined a neutral
temperature based on equal mixtures of boiling water and ice. However, he did not
have a thermometer so the temperature was presumably assessed with the physician’s
hand. A more sophisticated version of Galen’s scale of temperament surfaced again to
help physicians in the sixteenth century.
In the late sixteenth century the first thermoscopes appeared (see Figure 1.2). These
consisted of a glass bulb attached to a thin tube immersed in water. It is not certain
who the inventor was, perhaps Galileo, but it seems likely that he was inspired by the
pneumatic experiments of the Greeks Philo and Hero that were carried out in the first
and second centuries BC. Thermoscopes were used for 50 years or so for both medical
and meteorological experiments.