BRIDGMAN. — A SECONDARY MERCURY RESISTANCE GAUGE. 245 



-y- = b P + Cf, 



b = log- 1 4.5681 - 10, 

 -c = log- 1 9.2977 - 20. 



Now to find the changed specific volume resistance of mercury 

 we have 



-— = p + ap, 

 iio 



where A R s is the observed decrease of resistance corrected for changed 

 shape of glass, R is the initial resistance measured in the same glass, 

 a is the linear compressibility of the glass, and p has the meaning 

 already given, namely the observed proportional decrease of resist- 

 ance in the given capillary. But p has already been found in terms 

 of p, and a has just been given, so that we have the empirical formula 



L^Jk = a [0.02168 + 10*p f ], 

 K p 



where a and b have the values already given, namely, 



a = log 5.5242 -10 

 b = -log 6.2486 -10 



The slope of the curve, i. e., the instantaneous pressure coefficient at 

 any point, is: 



1 dR 

 — -~ = -a [0.02168 + 10 & p j 11 + | bpl log e 10}], 



where R s is the variable resistance corrected for the glass. The in- 

 stantaneous coefficient per unit resistance is at any point : 



_1_ dR, a [0.02168 4- 10 6p * {1 + f 6p* log e 10}] 



Rs dp 1 _ ap [0.02168 + 10 6 ?*] 



These three quantities were computed by the above formula and 

 are given in Table VII. They are also shown graphically in Figure 8, 



