356 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



BIBLIOGRAPHY. 



1. 1895: WARD. Preliminary notice of the Plymouth meteorite. Amer. Journ. Sci., 3d ser., vol. 49, pp. 53-65. 



(Cut of the mass and of an etched section). 



2. 1895: BREZINA. Wiener Sammlung, p. 285. 



3. 1895: COHEN. Meteoreiaen-Studien IV. Ann. K. K. Naturhist. Hofmus. Wien, Bd. 10, pp. 82 and 90. 



Polk County. See Fisher. 



PONCA CREEK. 



Holt County, Nebraska. 



Here also Dakota and Dacotah. 



Latitude 42 52' N., longitude 98 30' W. 



Iron. Coarsest octahedrite (Ogg) of Brezina; Braunite (type 3) of Meunier. 



Described 1863. 



Weight, 45 kgs. (100 Ibs.). 



This meteorite was described chiefly by Jackson, 1 as follows : 



On the 9th of June, 1863, 1 received, througn Messrs. John W. Shaw & Co. of this city, a mass of meteoric iron from 

 John B. Hoffman, Esq., United States Indian agent for the Ponca Tribe of Indians. This mass of metal was supposed 

 by Mr. Hoffman to be some native alloy of silver and it was sent here to be assayed for that metal. 



The mass in my possession weighs 10 pounds 10 ounces, and is 6 inches long, 5 inches wide, and about 2 inches 

 thick, but is of an irregular form, the weathered or exterior surface being much indented or wavy and pitted, while its 

 opposite side is columnar, a natural fissure having existed between it and the large mass from which it was detached by 

 the aid of a sledge hammer. It is stated that this piece was broken from a lump of the same kind which was estimated 

 to weigh 100 pounds. 



It was found on the surface of the ground in the Dakota Indian territory, 90 miles from any road or dwelling. 



Where it has been rubbed and partially polished the iron has a silvery appearance, and hence the mistake enter- 

 tained as to its probable nature. 



Excepting on the exterior of the columnar portions, which have a steel-like crust, the metal is very soft and saws or 

 files easily. It has a bright surface when cut. No earthy or stony matter has been found in it, and, judging from its 

 great density, it appears to be solid in its interior. Pieces were sawed off in different places and these were polished 

 and tested with dilute nitric acid for the production of Widmannstatten figures, but none have thus far been produced. 

 Only a scaly-like structure, quite fine, is developed by the acid, or when a lump of the iron is dissolved ridges and fine 

 projecting points are left on the undissolved metal. I noticed the singular phenomenon of the indifferent state of the 

 iron to nitric acid while dissolving this metal. After a rapid boiling effervescence with a rush of red fumes of nitric 

 acid the chemical action suddenly ceased and could not be renewed by the addition of more nitric acid nor by a boiling 

 heat, but on inclining the glass beaker so as to cause the metal to come in contact with the other side of the glass tumul- 

 tuous chemical action instantly commenced and the solution went on rapidly. This seems to show that the electrical 

 state of the metal and of the glass is concerned in the indifferent state of the metal to the acid. 



Qualitative examination soon demonstrated the existence of nickel, phosphorus, tin, cobalt, and chromium in 

 this meteorite. 



Its specific gravity, taken with much care, was found to be 7.952. Its hardness that of the softest malleable iron, 

 except on the exterior of the columnar portions, which were as hard as case-hardened iron, resisting the saw and causing 

 a sharp cry under the file. No carbon was found. 



The quantitative analysis was effected on two separate pieces, sawed from two of the columns, and the proportion 

 of nickel was twice determined, the iron in both cases being removed as a succinate by the well-known processes. 



By blowpipe examination, tin in metallic grains was obtained, and the presence of small proportions of cobalt 

 and chrome were proved. Phosphoric acid was found by molybdate of ammonia, and was in the analysis separated 

 in the state of pyrophosphate of magnesia. 



Although the analysis is not quite complete, yet it is enough so for our present purpose in demonstrating the 

 meteoric nature of this metallic mass under examination. 



The following are the percentage results of my analyses, executed on a gram in each trial: 



1 2 



Metallic iron 91. 735 91. 735 



Metallic nickel 6. 532 7. 080 



Tin 0. 063 0. 063 



Phosphorus 0. 010 0. 010 



98. 340 98. 888 



The cobalt was proved by the blue color the nickel gave with the borax bead; chrome, as shown by the bead of 

 the nickel oxide in microcosmic salt, the green color being persistent in the reducing flame and coming out as the red 

 color produced by the nickel in the hot bead faded. Chlorine was searched for in a solution of 53.7 grains of the 

 meteorite, but none was discovered. 



