190 SCIENCE OF COMMON THINGS. 



Determination of the boiling and freezing points. 



height. This, therefore, forms another fixed point on 

 the geometric scale, and is called the boiling voint. 



1356 How are the intermediate points determined ? 



In Fahrenheit's thermometer, the intervals on the 

 scale, between the freezing and boiling points, are 

 divided into 180 equal parts. This division is similarly 

 continued below the freezing point to the place 0, and 

 each division upwards from that is marked with the suc- 

 cessive number 1, 2, 3, etc. The freezing point will 

 now be the 32d division, and the boiling point will be 

 the 212th division. These divisions are called degrees, 

 and the boiling point will therefore be 212, and the 

 freezing temperature, 32. 



1557 When and by wham was the thermometer invented ? 



The thermometer was invented about the year 1600; 

 but, like many other inventions, the merit of its dis- 

 covery is not to be ascribed to one person, but to be 

 distributed among many. 



1558 Why is the thermometer in general use in the United States, 

 England, and Holland, called Fahrenheit's thermometer '? 



Because thermometers having a like graduation were 

 first manufactured by Fahrenheit, a Dutch philoso- 

 phical instrument-maker. The employment of mercury 

 as the most suitable fluid for the thermometer is also 

 usually attributed to him. 



IS 5 9 How many kinds of tliermorneters 

 are in general use ? 



Three : Fahrenheit's, Reau- 

 mur's, and the Centigrade ther- 

 mometer, or thermometer of 

 Celsius. 



126O What constitutes the di/erence 

 letween these instruments f 



The differences of graduation 

 between the freezing and boiling 

 points of water. Reaumur is 

 divided into eighty degrees, the 

 Centigrade into one hundred, 

 Fig 4L and Fahrenheit's into one hun* 



