58 Lloyd — Thermo-magnetic and Galvano- magnetic 



tivity for heat was first announced by Righi* and shortly 

 afterward by Leduc.f The Leduc effect has been observed by 

 LeduCj-f* Righi,J and van Everdingen.§ The J^ernst effect, 

 discovered by von Ettingshausen and NernstJ lias been 

 observed by van Everdingen, Yamaguchi,T[ Moreau** and the 

 writer, those observations covering a number of metals. The 

 Ettingshausen effect was observed by its discoverer f f in bis- 

 muth, antimony and tellurium, and was included in van Ever- 

 dingen's observations on bismuth. The longitudinal thermo- 

 magnetic effect has been observed in bismuth by von Ettings- 

 hausen and Nernst, van Everdingen,^ and Lownds.§§ 



Chemically pure tellurium was obtained from Eimer and 

 Amend, and cast into the form of a plate, 6*7 cm long, 2 5 cm 

 wide and 01 cm thick, with two lugs projecting from the middle 

 of the lateral edges. Six thermo electric couples of copper 

 and German silver wire made electric connection with the 

 plate; one to each of the lugs, the other four along the center 

 line of the plate, separated by distances of 15, 13, 18 mm . 

 These couples served to determine the temperature at the six 

 points and thus the temperature-gradient, and in addition could 

 be used to determine the difference of potential between any 

 two points. The ends of the tellurium plate were pressed 

 by springs against projections from two brass tubes, through 

 which steam and cold water, respectively, could be passed. 

 The whole was mounted on a wooden frame, and suspended 

 between the poles of a powerful electro-magnet. The pole- 

 faces were 6*3 cm square and l'3 cm apart, and the magnetic field 

 between them practically uniform. The strength of field was 

 determined from the resistance of a calibrated bismuth spiral 

 which was also attached to the wooden frame. When sending 

 an electric current through the plate, cold water flowed through 

 both brass tubes, to which the lead-wires were attached. Dif- 

 ferences of potential were measured by comparison with a 

 standard Clark cell, using the potentiometer. A very sensitive 

 astatic reflecting Thomson galvanometer was used as a current- 

 indicator. 



The electromotive force, E, in microvolts, of a thermo- 

 electric circuit of copper and German silver, one junction of 



*Rend. Ace. Lincei, iii, p. 481, 1887; Beiblatter, 11, p. 670. 

 f Comptes Rendus, civ, p. 1783, 1887. 

 X Rend. Ace. Lincei, iii, p. 6, 1887. 



§ Proc. Royal Acad. Sci. of Amsterdam, i, p. 72, 1898; Comm. from Leiden, 

 No. 42. 



|| Anz. d. kais. Akad. Wien, xiii, p. 114, 1886; Wied. Ann., xxix, p. 343. 



\ Ann. d. Physik, i, p. 214, 1900. 



** Journal de Physique ix, p. 497, 1900. 



•fi Wied. Ann., xxxi, p. 737, 1887. 



%X Ann. d. Physik, iv, p. 776, 1901. 



|§ Leiden Comm., No. 48 ; Proc. R. A. S. A., Mar. 25, 1899. 





