METEORITES OF NORTH AMERICA. 201 



structure of the meteorite, and the analysis, which was evidently merely a provisional one, indicates an unusually low 

 percentage of nickel and cobalt. 



Already the cursory examination of the etched section had given the unexpected and startling result that the 

 block possessed no individual structure. The difference is so marked that at first, as I possessed only sections cut from 

 both ends, I was convinced that a mistake had been made and that pieces of two different meteorites had been sent me. 

 Not until I reassembled all the fragments obtained by dissection (altogether 17.2 kg. with a section face of 1,537 sq. cm.) 

 did it become evident to me that here was a meteorite which was granular on one end and amorphous on the other. 

 Such a phenomenon appears never to have been observed before. 



Variation of structure has indeed been noted before in a few instances, but so far as can be determined from the 

 meager descriptions extant it has affected only a small area, so that the general character of the meteorite is unitary; 

 while in the present case the whole meteorite can be divided into two portions having different structure and in general 

 quite distinctly marked off from one another. Characteristics similar to those of Forsyth would be expected soonest in 

 the meteoric irons of Floyd Mountain, Holland's Store, and Summit; but whether such characteristics are actually 

 present can, naturally, only be determined definitely when each meteorite is as completely disclosed as happened in 

 the case of Forsyth. 



When, from the individual fragments into which Forsyth has been broken up, the original form has been recon- 

 structed, a three-sided, sharp-pointed pyramid is obtained whose lower half is semiglobular in form. On the thinner 

 end the nickel iron consists of small grains of nearly the same size. Most of them have a diameter of 0.25 to 0.5 mm.; 

 only in very isolated cases does it exceed this by a small amount, and the number of smaller grains lying between the 

 former is also comparatively small, so that from a not too exact observation of the structure it seems conspicuously of a 

 uniformly granular character. While the grains are, moreover, almost isometric they are not round, but with many 

 small excrescences. The larger number glisten at a certain position of the section. If the latter be examined under 

 a magnifying power of 50 diameters by reflected light it is evident that each grain possesses the same structure as the 

 rest of the iron, only very much finer. Each grain is composed of grains from 0.02 to 0.03 mm. in size, a portion of 

 which are more vigorously attacked by the etching than the rest, so that by sufficient magnifying power fine pittings 

 of apparently uniform size and distribution appear upon the surface. These pittings apparently produce the above- 

 mentioned sheen. They are scarcely bounded by crystal facets; then when the reflection is placed under the micro- 

 scope it returns first upon turning the section through 360°. 



This portion of Forsyth then may be designated, like Locust Grove, as "granular ataxite," a group which hitherto 

 has not been more sharply defined. The lower thick portion of the block is essentially different in character from that 

 of the upper sharp end. A section through the former upon etching takes on to the unaided eye an entirely homo- 

 geneous appearance, such as could be produced only by a very uniform fine structure. The etched surface appears 

 perfectly dense and dull, with a velvet-like luster, and seems exactly similar to the etching surface of a Babbs Mill 

 specimen. Under a very strong glass a very fine structure, as in the case of Babbs Mill, may be discerned; the indi- 

 vidual grains may measure 0.02 mm. 



The boundary between the denser and the more granular nickel iron runs somewhat like a cut aslant through the 

 pointed portion of the block, so that two pieces running to a sharp pointed wedge shape are formed, of which the densely 

 compacted part forms about six-sevenths and the granular part one-seventh of the meteorite. Of the pieces obtained 

 by division, therefore, one large end piece weighing 7.5 kg., the next largest sections (together weighing 3,600 gr.), 

 and a 11-cm. slice cut from the side and weighing 1.5 kg., are entirely or almost entirely amorphous. Thereupon follow 

 sections with small granular particles on the border until finally the latter predominate, and lastly the two end pieces 

 obtained from the pointed part of the pyramid are entirely granular. While the two sorts of nickel iron are sharply 

 marked off from one another in the larger portion, still the direction of the boundary face is very irregular in the smaller. 

 The granular and the amorphous portions penetrate one another in manifold bendings, and upon the section surface 

 numerous isolated granular particles lie in the amorphous portion, and vice versa. Often these are projecting portions 

 cut off by the section, but this is not always the case, since not infrequently toward the border the granular parts may 

 be seen to break up and resolve into small groups or even isolated grains until finally the amorphous iron alone prevails. 

 At the same time, however, the border remains ever distinct, inasmuch as there is no gradual diminution in the size 

 of the grains, but each isolated grain shows essentially the same size as individual grains in the aggregate, and the 

 differences in structure likewise remain entirely distinct. A figure gives a clear view of the character of the border, 

 the section being taken from the same portion of the meteorite in which both sorts of nickel iron are about equally well 

 developed. 



The granular and the amorphous nickel iron show remarkably different effects from treatment with hydrochloric 

 acid; the former is readily etched with dilute acid, the latter is only slowly attacked by concentrated acid. 



The number of accessory constituents, in respect to the abundance of the materials at disposal for investigation, is 

 small, section surfaces occurring of from 60 to 70 and even occasionally of 110 sq. cm. in size from which they are 

 entirely wanting. Troilite occurs most abundantly of all. The larger nodules are of an ellipsoidal form and attain a 

 length of 17 mm. and a breadth of 10 mm. When they are found near the border they are as a rule surrounded by a 

 broad, considerably rusted zone, and a portion of the latter may have been formed at the expense of the iron sulphide. 

 Occasionally in the large ones the boundary is very regularly ellipsoidal, in the small ones delicately bent. Many 

 particles of troilite are elongated and irregularly bounded; for example, there is one 15 mm. long and only from 1 to 

 2 mm. broad. Finally there are also small roundish grains with a diameter of 1 mm. and from that diminishing down 

 to mere points in size; to these belong small dark round specks. 



