52 



HEAT 



and may endanger our health by remaining in a room 

 which seems comfortable, when really it is too cold. 

 The thermometer is the only true guide to be followed 

 if we wish to know the real temperature. Of course, if 

 we are exercising, the temperature may be much below 

 68 degrees and do us no harm. The temperature of 68 

 degrees is proper for persons who are sitting still, or 

 moving about only a little. Is your room at the right 

 temperature? 



The following experiment will show you how little 

 it is possible to trust our feelings or sensations. 



Experiment 27. Hot or Cold? 



Apparatus : Three cups or other similar dishes, 

 sauce pan, alcohol or gas lamp, ring stand, wire gauze. 



Materials: Ice. 



a. Fill one cup with water which is as hot as you 

 can bear putting your hand into ; fill the 

 second cup with water at the temper- 

 ature of the room ; the third cup should 

 be rilled with ice cold water. Place the 

 fingers of one hand in the hot water and 

 those of the other hand in the very cold 

 water and let them remain for one full 

 minute. Then place the fingers of both 

 hands in the cup containing the water ar 

 the temperature of the room. How do 

 the fingers feel? Is the last water hot 

 or cold? Can you trust your sensations? 



Review Questions, 12. 



1. If the sun rises at seven o'clock, at what time 

 will it set? 



