CHAPTER V 



MEASUREMENT OF TEMPERATURE 

 THERMOMETRY 



Introduction. Some very common expressions fre- 

 quently heard are, "it's as cold as ice" or "it's boiling 

 hot." Such expressions are relative and compare the 

 temperature of a substance with the known tempera- 

 ture of ice or boiling water. Thus it will be seen that 

 by temperature is meant how hot or how cold a given 

 substance is. 



Galileo's thermometer. To-day we are supplied with 

 instruments by which the hotness 

 or coldness of a substance may be 

 definitely determined. But such 

 was not always the case. In fact, 

 the earliest attempt to measure 

 temperature was made the latter 

 part of the sixteenth century 

 (1592) by Galileo, an Italian 

 scientist. 



His instrument was known as the 

 gas or air thermometer. He had 

 observed and knew well that sub- 

 stances change in volume with a 

 26 



Fig. 15. Air thermom- 

 eter made by Galileo. 



