634 



KANSAS CITY REVIEW OF SCIENCE. 



the Lyons Academy substituted mercury for the alcohol, introducing a quantity 

 whose volume might be represented by 6600 at the temperature of freezing 

 water. Having raised this to the temperature of boiling water he found the 

 volume of the mercury increased to 6700, or 100 parts. This suggested the 

 division of the tube between these fixed points into 100°; and this, according to 

 this authority, was the origin of the Centigrade thermometer ; although as before 

 stated, its invention is generally credited to Celsus about six years later. 



360° Circle. 

 180 Diameter. 

 212— 32 equals 180 



O 



WATER FBEEZES. 



Zero— Artificial cold, produced 

 by Fahrenheit. 



Fahrenheit kept the reason for his graduation of the thermometer a secret^ 

 and it has been supposed that his zero point, 32° below freezing, was the lowest 



