CHAPTER XIV. 

 MEASUREMENT OF TEMPERATURE. 



29. TEMPERATURE AND THERMOMETERS. 



i. The sense of feeling may be deceived. Arrange three basins in a 

 row ; into the first put water as hot as the hand can bear, into the second 

 put lukewarm water, and fill the third with cold 

 water. Place the right hand into the cold water 

 and the left into the hot, and after half a minute 

 quickly put both into the lukewarm water. The 

 left hand feels cold and the right hand warm while 

 in the same water. 



ii. Measuring temperature. (a) Place the flask 

 of water, with fitted tube used in Expt. 28, ii. (a), 

 in hot water, and notice the height of the liquid 

 in the tube. Transfer it to cold water, and observe 

 that the liquid in the tube sinks. 



(6) Procure, or make, a thermometer tube with 

 a bulb at one end. With a little practice it is 

 easy to blow a bulb upon a piece of thermometer 

 tubing. One end of the tubing is held in a blow- 

 pipe flame and twirled round until the glass melts 

 and runs together so as to seal up the tube. A 

 small blob of glass is then allowed to form, and 

 while the glass is molten the tube is taken out of 

 the flame and blown into steadily. To introduce 

 mercury afterwards, heat the bulb and while it is 

 hot invert it and put the open end into mercury. 

 As the bulb cools, mercury will rise in the tube 

 and take the place of the air driven out of the tube 

 by heat. Repeat the operation until the mercury 

 fills the bulb and part of the stem. 



(c) Place in hot water the bulb of the instru- 

 ment just constructed, and make a mark at the 

 level of the mercury in the tube. Now place the 

 instrument in cold water, and notice that the 

 mercury sinks in the tube. The mercury is thus 

 seen to expand when heated and contract when 



FIG. 61. Thermometers 

 of the form used for 



(d) Examine a thermometer. Notice that it is scientific work. 



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