66 



SCIENCE PROGRESS. 



OBSERVATIONS. 



Reading (stem vertical and all at one temp.) 25*61 5 

 . Barometer (corrected) . . . .754-8 m.m. 



Distance from centre of bulb to surface of 



water ...... 400 m m. 



The thermometer was then placed in melting ice, and 

 watched until the lowest point touched by the column was 

 ascertained. 



Reading (stem vertical) .... 0-051 : 

 R Barometer (corrected) . 754*8 m.m. 



\ 



Distance from centre of bulb to surface of 



water ...... 66 m.m. 



A 



B 



CORRECTIONS. 



'External pressure = 754*8 + \%\ 

 Hence external pressure correction 

 Internal pressure correction . 



.Calibration correction 



' 7 S4*2 m.m. 



7" 



— - o*oo3 c 

 = + 0-04 1 c 

 = + 0-004° 



External pressure = 754*8 + T \\ 

 Hence external pressure correction 

 Observed zero depression 

 Calibration correction 

 Internal pressure correction 



Hence true zero depression 

 Hence sum of corrections from A and B 

 Hence corrected reading- = 25*6 1 5 + 0*085 

 Fundamental error .... 



Temperature on true mercury scale 

 Correction to hydrogen scale . 



sum = + 0*042 



= 7597 m.m. 

 = o*ooo° 



= -0-051 



= o-ooo° 

 = +0-008° 



= -0*043° 

 = + 0-085 



= 25700 



= - O'OI I 



= 25-689° 



= — 0-096° 



25'593 



True temperature on hydrogen scale 



Had the temperature not been steady, a further correc- 

 tion depending on the rate of rise would have had to be 

 included. 



Although in the above example many of the corrections 

 are of opposite signs and the total effect small, this is not 



