762 THERMOMETRIC SCALES. 



openings of vessels or pushed through corks, by which 

 vessels or flasks are closed. For our experiments one 

 or two of this kind will be the most suitable. 



On the scale of each thermometer two fixed points 

 are marked first. These are the freezing point and the 

 boiling point of water. The distance between these 

 two points is divided into a definite number of equal 

 parts, called c degrees.' On the Continent, and more 

 especially in France, this space is divided into 100 

 parts, and this division is called the Centigrade, or, from 

 its inventor, the Celsius scale. The Centigrade thermo- 

 meter is now almost exclusively adopted for scientific 

 purposes, and will be used in this work. On this 

 scale the freezing point of water is denoted by zero, 

 and called 0; the boiling point is called 100; the 

 space between the fixed points is divided into 100 

 parts of equal capacity, and the division is carried on 

 through the length of the scale below and above 100. 

 To indicate temperatures below zero a minus sign ( ) 

 is placed before the corresponding figures ; thus 5 

 signifies 5 degrees below zero, or, as it is often expressed 

 (though incorrectly), 'five degrees of cold.' 



In Germany Reaumur's scale is still used for many 

 ordinary purposes. The freezing point is denoted by 0, 

 as in the Centigrade scale, but the boiling point is 

 marked 80, and the distance between these points is 

 divided into 80 instead of into 100; that is to say, 

 80 degrees Reaumur are equal to 100 degrees Centigrade. 



One degree Reaumur is thus equal to - - = of a 

 degree Centigrade, and one degree Centigrade is equal 



Q C\ A 



to - = . of a degree Reaumur ; or, as usually stated, 

 100 5 



