THERMOMETERS. 



467 



TABLE CLX. BOILING POINT OF WATER UNDER DIFFERENT 

 PRESSURES (due to Regnault). 



The difference between the observed boiling and freezing points is taken, 

 divided by 100 (or 180 if a Fahrenheit thermometer is used) ; the values in 

 mean degrees of the scale from to 10, 10 to 20, etc., are multiplied by the 

 value thus obtained, and the corrected value tabulated. The differences 

 between these and the nominal values of the scale are now plotted on 

 squared paper, and will serve as a curve of correction of the instrument. 



It is advisable to redetermine the boiling and freezing points from time 

 to time, as they are liable to slight alteration. 



Other thermometers may be standardised by comparison with this one. 



