BRIDGMAN. — A SECONDARY MERCURY RESISTANCE GAUGE. 239 



observed values and the values calculated by the above formula, 

 together with the discrepancies. The divergence is rarely more than 

 iV per cent and seems irregular in sign. The fairly high discrepancy 

 at 6800 is doubtless because this pressure was reached with only one 

 of the absolute gauges, while all the other values are means of two 



TABLE IV. 



Comparison of Observed Pressure with that calculated from 



the Change of Resistance. 



determinations. The probable error of the formula itself, calculated 

 by the formula for the error of the mean, is ^ per cent. 



The above formula gives the measured change in the resistance of 

 mercury in a specified glass envelope at 25° in terms of the pressure. 

 In practice, it will be necessary to compute the pressure, given the 

 measured change of resistance. The above formula cannot be easily 



