chap, xxxvi.] THERMOMETRIC SCALES. 



469 



than mercury or alcohol. Thermometers may be 

 made to register their elevations by means of an 

 index, a short thread of mercury which is pushed 

 up by the expanding mercury, and when the mercury 



I 

 S. 



212 



E 



3 

 



K 



contracts the index is left registering the highest 

 point to which it rose in the tube. In other ways 

 also thermometers may be made self-registering. 



More delicate thermometers than those described 

 are made, which register differences of temperature of 

 a much smaller range than between and 100. 

 Thus mercury thermometers made of tubing with 

 a very fine bore, and with a bulb of very thin 

 walls, are capable of measuring with rapidity very 



