( 771 ) 



thermometer-temperatures, the value of jwa at t s now follows from 

 the formula 



(pv A )t s = (pv A ), (1 + 0.0036627 t s ). 



§ 11. Probable error of a determination. 



The mean error in the calibration of the large volume of the piezo- 

 meter may be estimated at ± ■■..- . As to the volume into which the 



4000 



gas is compressed during the measurements, the greater density 

 of the gas in the reservoir at low temperatures may be allowed 



for by reckoning only with - of the amount of the volumes at the 



o 



temperature of the room. The errors in these volumes being predo- 

 minant with respect to those in the volume of the piezometer reser- 

 voir, the mean error for measurements below — 180° with piezo- 

 meters of 5 c.M 3 may be put equal to ± of the compressed 



volume in accordance with the degree of accuracy as was calculated in 

 Comm. N°. 69, where for measurements at the ordinary temperature 



the mean error is estimated at ± for piezometers of 5 c.M 8 . 



1000 F 



For — 100° the mean error will be ± . 



2000 



The mean error of the determinations of the normal volume is 



± , that of the measurements of the pressure may also be 



3000 F J 



1 

 estimated at ± 



3000 



In the determination of the temperature there is no appreciable 

 error. The observations made for one point show that the mean error 

 due to variations of temperature and faulty readings of the position 



of the mercury in the stem, may be put smaller than ± . 



J > J F 5000 



The mean error of the determination of temperature in the stem 



1 



remains below db . 



6000 



The mean error caused by all these sources of errors together 



1 

 amounts to ± — — for piezometers of 5 c.M. 3 and not very low 

 1500 J 



1 „ 

 temperature, to ± 7^777 i° r larger piezometers and very low tempe- 



