430 



SCIENCE. 



[N. S. Vol. XV. No. 376. 



the wrong direction for so many years; the 

 extensive and nearly simultaneous researches 

 of Dr. Barus in the Geological Survey and 

 Holborn and Wien in the German Reichsan- 

 stalt; and finally the successful return to first 

 principles at the Reichsanstalt, with the help 

 of the electric oven and the experience of the 

 long line of distinguished predecessors, in 

 which the speaker himself had a part. 



The various methods for carrying pyromet- 

 ric measurement beyond the range of the gas 

 thermometer by making direct comparisons 

 with it as far as it is available, and extra- 

 polating the empirical relation thus obtained, 

 were then taken up; VioUe's calorimetric 

 method, by which he obtained the results gen- 

 erally accepted for twenty-five years or more; 

 the electrical resistance method (Siemens, Oal- 

 lendar and others), depending upon the varia- 

 tion in the resistance of a platinum wire with 

 the temperature; the thermoelectric method 

 (Barus, Holborn and Wien, and others), 

 depending upon the electromotive force devel- 

 oped in a pair of wires (pi 90 rh 10 — pt 10 

 usually) whose junctions are maintained at 

 different temperatures ; and several others. In 

 closing, some recently published optical meth- 

 ods were reviewed (Berthelot, Lummer, Hol- 

 born and Kurlbaum) which promise to extend 

 the upper limit of measurable temperatures 

 almost indefinitely though with what accuracy, 

 in view of the extent of the extrapolation 

 necessary, it is hardly possible yet to say. 



Dr. Day gave as the approximate limit of 

 accuracy of the best methods now available 

 ±1° up to 1000°, d= 10° to perhaps 1600°, ±100° 

 to 3000° or more. He did not consider that 

 the limit had been reached either in the accu- 

 racy or range of i^yrometric measurement or 

 even of gas thermometry and expressed regret 

 that no more attention was being paid to so 

 promising a field in this country. 



Dr. L. A. Bauer presented a paper on 

 'Energy and Entropy: Their Role in Thermo- 

 dynamics and Thermochemistry.' As sug- 

 gested by the title, the respective roles played 

 by the two fundamental principles of thermo- 

 dynamics, the principle of the conservation of 

 energy and the principle of the increase of 

 entropy, were set forth and elucidated by 



examples. It was shown that as much is 

 known about the physical properties of entropy 

 as of energy, and that in the phenomena of 

 heat the entropy principle first comes into 

 play, prescribing the direction or method in 

 which stable equilibrium can take place. 

 After the state of equilibrium has been 

 reached then the principle of energy can be 

 applied. It was shown that it would be a 

 gain, now that the entropy function has been 

 found, to discard the historical method of 

 establishing the entropy principle and instead 

 adopt a method similar to that followed by 

 Hertz with regard to the fundamental equa- 

 tions of eleetromagnetism — i. e., begin with an 

 equation expressing a relation between the 

 specific heats at constant pressure and at con- 

 stant volume which admits of experimental 

 proof and which prescribes 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. 



A relationship between entropy and the 

 term introduced by Helmholtz — warmegehalt, 

 changed by von Bezold to potential tempera- 

 ture and used by him extensively in his paper 

 on the 'thermodynamics of the atmosphere,' 

 was established and the name entropic temper- 

 ature in place of potential temperature sug- 

 gested. ' Charles K. Wead, 



Secretarji. 



DISCUSSION AND CORRESPONDENCE. 



AGRICULTURE AND THE EXPERIMENT STATIOKS. 



The agricultural experiment stations of the 

 United States, which the Federal Government 

 has established in the several States, have now 

 themselves passed the experimental stage and 

 have to a remarkable degree won the respect 

 and confidence of the farming and allied in- 

 terests which it is their function to serve. 

 There are at present fifty-nine experiment 

 stations more or less completely maintained 

 by Federal funds, two of which are colonial, 

 and one of which is in Alaska. The organiza- 

 tion and location of the continental stations 

 affords an interesting example of the effect of 

 the application of political conceptions to 

 scientific investigation. 



