AND STATICS UNDER THE INFLUENCE OF LIGHT. 
367 
h" is the variation of the barometer on passing from t to r", when the 
correction for the temperature of the mercury is also made. This correction 
must be added to the observed tt’-tt" ; it is for the same day, when the 
barometer changes very little, of little importance; on the contrary, it 
becomes important for the ordinary changes of the barometer. 
7 j" cmr , is the true variation in the height of the manometer, if the atmospheric 
pressure and the temperature of the bath (or of the gas mixture) should 
have remained constant the whole time, i.e., after the corrections for the 
variations of the temperature of the bath and for the atmospheric pressure 
were made. Results were not reduced to normal atmospheric pressure, since 
this would not serve any purpose (see Table I.). 
