E. H. Rail— Effect of Magnetic Force, etc. 277 



surface is irregularly pitted, the largest of the pits being 3 cm 

 by 2 cm and very deep for their size. No troilite was observed 

 either in the cutting or in the pitting. This iron is one of the 

 Braunite group of Meunier. 



When etched with dilute nitric acid this iron does not show 

 the Widmanstatten figures, but under the glass the markings 

 are seen to be similar to the Braunau Hauptmanndorff iron de- 

 scribed by Tschermak* and Huntington, f (see figure 4). This 

 beautiful structure is broken only by the thin layers of schrei- 

 bersite, which divide a surface 25 mm square into over twenty- 

 five irregular crystalline parts. 



The specific gravity is 7*630. The following analysis was 

 kindly made by Mr. Howard L. Mcllvain : 



Silver Crown. Rowton,:}: Charlotte, § Jewel Hill,| 



Flight. Smith. Smith. 



Iron 91-57 91*25 91*15 91*12 



Nickel 8*31 8*582 8*05 1-82 



Cobalt trace 0*371 0*72 0*43 



Phosphorus.. *07 0*06 0*08 



Carbon trace .... 



9995 99*98 99 45 



It approaches more closely to the Rowton, Charlotte and 

 Jewel Hill meteorites in composition. 



I take pleasure in thanking Dr. Wilbur C. Knight for assist- 

 ance in securing the iron, and Mr. Howard L. Mcllvain for 

 the analysis. 



Art. XXX. — Experiments on the Effect of Magnetic Force 

 on the Equipotential Lines of an Electric Current / by E. 

 H. Hall, Assistant Professor of Physics in Harvard College. 



[Continued from the August number of this Journal, p. 146.] 



The next to the last column in this table (August number) 

 shows that the intensity of magnetic induction in the thin cross 

 remains throughout very nearly the same as that of the mag- 

 netizing field, but the intensity of magnetic induction in the 

 thick cross, about If times as great as that of the magnetizing 

 field when this is weakest, falls to a value about 1-J times as 

 great as that of the magnetizing field when this is strongest. 

 The intensity thus attained is about 22000 c. g. s. units, a not- 

 ably high one. If 



* Sitzungsber. Akad. Wiss., Wien, lxx, Abth. i., p. 449. 



f Proc. Amer. Acad. Arts and Sciences, May 12, 1886, p. 478. 



\ Trans. Royal Soc, Feb. 9, 1882. § This Journal, III, vol. x, p. 349. 



|| Ibid., II, xxxix, p. 24. 



"*|[ There may be a constant error of several per ceat in the values of magnetic 

 induction given in this article, as the area of the little test-coil used between the 

 poles of the magnet is difficult to measure accurately. 



