IIl8 APPENDICES AND TABLES 



APPENDIX D 



COMPAEISON OF THE SCALES OF FAHRENHEIT'S, THE 

 CENTIGRADE, AND REAUMUR'S THERMOMETERS 



THESE three thermometers are graduated so that the range of temperature 

 between the freezing and boiling points of water is divided by Fahrenheit's 

 scale into 180 (from 32 to 212), by the Centigrade into 100 (from to 

 100), and by that of Reaumur into 80 (from to 80) portions or degrees. 

 Hence we derive the following equivalents : 



A degree of Fahrenheit is equal to '5 of the Centigrade, or to '4 of 

 Reaumur's ; a degree of the Centigrade is equal to 1'8 of Fahrenheit's, or 

 to '8 of Reaumur's; and a degree of Reaumur's is equal to 2'25 of 

 Fahrenheit's, or to 1-25 of the Centigrade. 



To convert degrees of Fahrenheit into the Centigrade or Reaumur's, 

 subtract 32 and multiply the remainder by f for the Centigrade, or f for 

 Reaumur's. 



To convert degrees of the Centigrade or Reaumur's into Fahrenheit's, 

 multiply the Centigrade by f , or Reaumur's by f , as the case may be, 

 and add 32 to the product. 



EXAMPLE 



Let F, C, and R = the number of degrees Fahrenheit, Centigrade, and 

 Reaumur respectively. Then 



- - 



5 4 



r _5 (F-32). r _5R 



~9~ IT 



R _4(F-32). -R-4C. 



-Q- "5" ! 



F = C + R + 32. 



This last formula is of use, because in England thermometers are 

 usually graduated in Fahrenheit and Centigrade. Reaumur may be found 

 by inspection by subtracting the Centigrade from the Fahrenheit and 

 taking 32 from the remainder. On the Continent thermometers are 

 generally graduated in Reaumur and Centigrade. Fahrenheit can be found 

 by adding Reaumur and Centigrade and 32. Example : If the thermometer 

 reads 8 Reaumur and 10 Centigrade, the Fahrenheit will be 



8 + 10 + 32 = 50 F. 



