362 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



PUTNAM COUNTY. 



Putnam County, Georgia. 



Latitude 33 18' N., longitude 83 35' W. 



Iron. Fine octahedrite (Of) of Brezina; Dicksonite (type 12) of Meunier. 



Found 1839; described 1854. 



Weight, 32.5 kgs. (72 Ibs.). , 



This meteorite was first described by Willet, 1 as follows: 



This interesting meteoric iron, the first that has been found in Georgia, was presented to Mercer University by 

 John A. Cogburn in the fall of 1852. 



The circumstances of its discovery, as detailed by Mr. Cogburn, are briefly these: The iron was first observed by 

 his overseer in 1839 in a field which had been cultivated for several years, but was supposed to be the common black 

 rock of that region. Mr. Cogburn first noticed it in March, 1840, and attempting to raise it from the ground, found it 

 so heavy that he carried it to his blacksmith shop to have it broken. Its weight at that time was 72 pounds, and the 

 mass was coated deeply with a brown scaly crust. He attempted to break it upon an anvil, but could remove only 

 the outside crust, including a large blister, the place of which is now indicated by a deep fissure. Finding it so untract- 

 able, he threw it into his yard, where it lay neglected until a knowledge of the fact led me to request him to send it 

 to the University for examination. He states further that he supposes it to have been originally buried and brought 

 to the surface of the earth by cultivation and the action of rains; that there is no tradition of its fall; and that no simi- 

 lar pieces have been found in the neighborhood. 



Its weight, when it was brought to the University, was about 60 pounds. In shape it represents a rude triangular 

 pyramid, with its base and edges rounded, and its faces exposing many knobs and depressions. 



Most of the crust has been removed by the rough handling which it has received. The outer layers of what 

 remains separate in thin scales of no regular shape; the inner portions break into rhombohedral masses, which, under 

 the influence of a magnet, become permanently magnetic, showing that the iron has been converted into magnetic 

 oxide. The mass of iron exhibits no magnetism. 



In removing a dab, the iron was found to be remarkably tough and compact. The torn edges oxidized rapidly 

 and developed the crystalline structure before the application of acid; the oxidation proceeded inwardly from the 

 edges, following the lines of cleavage first, and afterwards spreading over the inclosed areas. The sawn surfaces, 

 after a few days exposure, were found bedewed with drops of a liquid, supposed to be chloride of iron. After longer 

 exposure the exudation ceased a point of striking similarity with the Texas iron. The polished surface is uniform, 

 without markings, and with few flaws. 



Hydrochloric acid applied to the heated slab attacks it with a rapid evolution of hydrogen bubbles, but develops 

 only a few of the larger bars, and the crystalline structure of the mass might be overlooked with the action of this acid 

 alone. Nitric acid, however, brings out the Widmannstatten figures most beautifully. The etched surface is a perfect 

 miniature copy of the Texan iron; the largest bars of the Putnam County iron corresponding with those of medium 

 size in the Texas iron, and thence diminishing to bundles of strise hardly visible to the naked eye. The triangles and 

 parallelograms are proportionally small. Query: Are the crystalline figures of meteoric irons in any degree proportional 

 to the meteoric masses? If so, may we not infer from the size of them whether the iron be an entire mass or a fragment 

 of a large one? 



Neutral sulphate of copper produces no precipitate of metal on the iron, the slightest addition of acid causes the 

 deposit of copper. Moreover, I find that if the film of copper be wiped off as soon as formed, the sulphuric acid has 

 etched out the figures superficially but very imperfectly. Liquid sulphuric acid when cold has no effect upon the 

 surface. 



In addition to the above description, I subjoin an interesting note from Professor Shepard, containing an analysis of 

 the iron, which he has very kindly furnished at my request. 



" In comparing the Putnam County meteoric iron with specimens from other localities, I notice a striking similarity 

 in its structure to that of the Texan mass. Like it, your iron is compact, nearly free from pyrites, and but slightly dis- 

 posed to rust on exposure to the air. But the resemblance between the two is seen to the greatest ad vantage, when etched 

 samples are compared with one another. The Putnam County iron exhibits figures of the same shape and size as the 

 Texas, viz, triangles and oblique-angled parallelograms bounded by slightly-raised edges which are often wavy, and 

 sometimes not continuously of the same thickness, but here and there bulging out into beads or knobs. The pyrites 

 in my specimens is scarcely to be recognized, except in one or two very limited patches which are irregular and 

 veinlike. 



" The iron appears to have suffered a very remarkable disintegration to the depth of half an inch or more below the 

 thick, scaly crust with which the mass was coated, in consequence of which it cleaves very regularly like the Cocke 

 County, Tennessee, iron into tetrahedral and rhomboidal fragments. 



"The specific gravity of the fresh internal portions of the mass is 7.69. A single analysis gave me the following 

 result: 



Iron 89.52 



Nickel, with traces of cobalt 8. 82 



Tin, phosphorus, sulphur, magnesium, and calcium * . 1. 66 



100.00 



