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PHILOSOPHICAL SOCIETY OP WASHINGTON. 
specific heats, radiation, viscosity, electrical resistance, and 
thermo-electricity. The most precise instrument is the nitrogen 
thermometer with platinum bulb, which is accurate to 1° up to 
1200° C. [Published in part in the Physical Review, vol. xix, 
p. 177 (1904).] 
547th Meeting. February 15, 1902. 
Vice-President Gore in the chair. 
Thirty-three persons present. 
Mr. A. L. Day continued his paper on The measurement of 
high temperatures. He said that above the limit of the nitrogen 
thermometer, say 1000° C., platinum-resistance-thermometers or 
pt.-pt.-rhodium thermo-couples are used; these go to 1600°, with 
an accuracy of about ±10°. Still higher are the optical methods, 
as Berthelot’s interference method, and the one depending on 
radiation from a black body, developed by Stefan, Boltzman, and 
Wien ; by these, measures may be made to 3000° or more with an 
accuracy of ± 100°. 
Mr. L. A. Bauer read a paper on Energy and entropy; their 
role in thermodynamics and thermochemistry. He pointed out 
that in heat-phenomena theiprinciple of increase of entropy first 
comes into play prescribing the direction or method of the 
change, and after a state of stable equilibrium has been reached 
the principle of conservation of energy can be applied. He 
further pointed out that it would be a gain now to discard the 
historical method of establishing the entropy principle, and 
begin with an equation expressing a relation between the two 
specific heats which admits of experimental proof, and pre¬ 
scribes that the entropy function has the same essential property 
as energy, viz., of being independent of the path or process used 
in going from one state to another. [Not published.] 
The subject was discussed by Messrs. Baker and Gore. 
The Chairman announced the presence of M. C. A. Laisant, 
examinateur d’admission a FEcole Polytechnique, Paris. 
