The Corbirto Effect in Iron. 677 



At high temperatures, when the refractive index of 

 glycerine has become greater than that of turpentine 

 throughout the spectrum, the mixture of these liquids has a 

 peculiar sparkling appearance, due probably to the formation 

 of caustics similar to the rainbow at very small angles. On 

 account of the small difference of refractive indices, the 

 caustics of different orders are formed in such quick 

 succession that they may interfere with each other. In the 

 case of a glass cylinder immersed in a liquid of slightly 

 lower refractive index, this gives rise to a set of fringes 

 which differ markedly from those in the case when the 

 cylinder has a lower index of refraction. They are broad at 

 small angles and rapidly decrease in width with increasing- 

 obliquity. Unfortunately, however, for want of an optically 

 good cylinder, the phenomenon could not be studied 

 thoroughly. 



In conclusion, the writer must express his cordial thanks 

 to Prof. C. V. Raman for suggesting this investigation and 

 for his encouraoino- interest in the work, which was carried out 

 in the Laboratory of the Indian Association for the Cultivation 

 of Science, Calcutta. 



April 14th, 1921. 



LXXVII. The Corbino Effect in Iron. 

 By E. P. Adams * 



BY the Corbino effect is understood the production of a 

 circular electric current in a metallic disk when a radial 

 electric current flows through it and a magnetic field is 

 applied at right angles to the plane of the disk. In a series 

 of papers by Dr. A. K. Chapman and the writer f it has been 

 shown that the Corbino effect is, essentially, the same as the 

 Hall effect, hut measured in a wholly different way. 



In measuring the Corbino effect in an iron disk at low 

 magnetic fields, Dr. Chapman 1 found that the effect appa- 

 rently reversed in sign at a field of about 260 e. in. units. 

 This reversal would have an important bearing upon the 

 theory of the galvanomagnetic effects if it were a true effect. 



* Communicated by the Author. 



t Phil. Mag. xxvii. p. l>44 ; xxviii. p. 692 (1914). Proc. Am. Phil. 

 Soc. liv. p. 47 (1915). 



X Phil. Mag. xxxii. p. 303 (1910). 



