JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. I, OCTOBER 19, 1911. No. 6 



PHYSICS. — The "correction for emergent stem" of the mercurial 

 thermometer. E. Buckingham. Communicated by C. W. 

 Waidner. To appear in the Bulletin of the Bureau of Stand- 

 ards. 



In defining the scale of the mercurial thermometer it is assumed 

 that the thermometer is all at the same temperature, as is the case 

 with "total immersion" in a bath of uniform temperature. When 

 a thermometer is standardized, the corrections are nearly always 

 stated for total immersion and in terms of the standard gas scale 

 of the laboratory where the test is made. If, subsequently, the 

 thermometer is used with only partial immersion, the mean tem- 

 perature of the emergent stem will be different from the temperature 

 of the bulb which it is desired to determine; and to allow for this 

 departure from the condition of total immersion, a "stem correc- 

 tion" must be applied to the observed reading before the correc- 

 tions given by the standardization become applicable. 



The length, A, of this stem correction is given by the equation 



A = l(t-f)a (1) 



and its value, K, in degrees, by the equation 



K= nl{t-f)a (2) 



in which n is the number of degrees per unit length of the stem at 

 the level where the reading is made, I is the length of the emer- 

 gent stem, t is the true temperature of the bulb, and a is the mean 



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