88 BULiLETIN" IS 4, UNITED STATES NATIOXiAl, MUSEiUM 



bersite (pis. 3, 51), the needles themselves showing no iron-phosphide 

 eutectic structures, which would be present if the kamacite had been 

 rejected from an iron-phosphide liquid solution. 



In such cases the only explanation would seem to be that such 

 nonmetallic inclusions served as nuclei around which the gamma- 

 alpha transformation was initiated and a more copious separation 

 of the kamacite was promoted. Such a process might also account 

 for the fact that in many ataxites small kamacite bodies often enclose 

 minute cores of iron-phosphide eutectic. 



XVI. NEUMANN LINES AND DEFORMATIONS 



In both meteoric nickel-iron and in the ferrite of artificial irons 

 fuie parallel lines are often observed which are called Neumann lines, 

 so named after J. Neumann, who discovered them m 1848 in the 

 Braunau hexahedrite. 



In artificial irons they are commonly designated by metallographers 

 as Neumann bands, but in the literature of meteorites they have 

 been uniformly termed lines ever smce their discovery. Neither 

 term exactly describes them, because both in natural and artificial 

 irons they may appear as exceedingly fine lines or as double lines or 

 bands of varying width. In this work it seems best to retain the 

 original designation, in conformity with the practice of writers on 

 meteorites. 



Occurrence. — In ferrite, which is granular, the lines are parallel in 

 each grain but diversely oriented in different grains. Sometimes a 

 grain shows more than one set of lines. The same is true of granular 

 meteoric irons in most cases. In hexahedrites grains are often absent, 

 and there is a homogeneous or unigrain condition not found in arti- 

 ficial irons; therefore the lines, not interrupted by grain boundaries, 

 may be parallel throughout the mass. They often are visible to 

 the eye on an etched surface. 



In octahedrites Neumann lines appear, often conspicuously, in 

 the kamacite bands. In octahedrites they are identical with those 

 in hexahedrites, but they usually are interrupted by taenit^ lamellae 

 so that adjacent kamacite bands have different sets of lines. Ex- 

 ceptionally they run across several bands with little or no interrup- 

 tion or change of direction. In the grams of granulated kamacite 

 bands they usually are diversely oriented, and the same is true of 

 many granular hexahedrites. Often, however, they run without 

 change across a number of grains in hexahedrites and also across 

 the large grains in some of the coarser octahedrites. 



It has been stated that Neumann lines are not found in ataxites; 

 yet exceptionally they are present in nickel-poor ataxites, as in 

 Forsyth County (pi. 8). This iron presents a homogeneous mass of 



