CHAPTER VIII 

 THE MEASUREMENT OF TEMPERATURE 



45. How Measured. In the measurement of temperature, 

 we have to deal with the effects of an addition of energy to 

 matter. It is more convenient to measure the effect of 

 energy upon matter than to measure the energy direct. The 

 instrument with which we now ascertain the temperature of an 

 object is called a thermometer. This instrument was not in- 

 vented until about a hundred years after Columbus discovered 

 America. Before that time, people had to depend upon their 

 bodily feelings for information of this nature and such methods 

 are still in use for roughly estimating temperature, as when we 

 touch an object with the hand to see if it is warm or cold. 

 This, however, is a very unreliable method of testing because 

 our temperature sense is easily deceived. If we hold one hand 

 in a basin of hot water for a time and the other hand in a 

 basin of cold water, and then put both hands into a vessel 

 of water at room temperature, the hand that was in the hot 

 water will now feel cold and the one that was in the cold 

 water will feel warm, though they are both in water of the 

 same temperature (83). 



46. The Therommeter. Thermometers may be made of 

 any substance that expands and contracts quickly with varia- 

 tions in temperature, but the substances most used are mer- 

 cury and alcohol. The ordinary thermometer consists of a 

 slender glass tube closed at the upper end, with a bulb at the 

 lower end containing either of the two liquids mentioned. If 

 alcohol is used, it is generally colored so that it may be more 



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