232 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



distinguishes three species — those containing much, little, or but very little iron, so that it can only be recognized by a 

 magnifier or a microscope; these species he designates as "Poly-," "Oligo-," and "Krypto-Sporadosideres." Accord- 

 ingly the Iowa County meteorites are "Oligo-Sporadosideres." 



The following table gives the result of my analyses of the average composition of the Iowa County meteorites: 



Nonmetallic — Iron. Nickel. 



Troilite 1.1 



Hyalosiderite 



Hypersthene 



Loss, traces 



Sum 1.1 



Magnetic — 

 Nickelif erous iron 6.6 0. 9 



Total 7.7 .9 



The Iowa County meteorites are "Oligo-Sporadosideres;" that is, meteoric stones containing but little plainly 

 visible metallic iron in detached grains. They contain 7 per cent by weight of metallic iron. Specific gravity, 3.57. 



The fracture is very rough and uneven, showing the lustrous metallic iron and lighter gray chondri (the chondrites 

 of G. Rose). The grains of lighter color contain less of iron silicate, but are otherwise composed of the same minerals, 

 namely, olivine (soluble in HC1) and pyroxenes (insoluble in HC1) besides some troilite. 



fTroilite L 8 Wluble =54 7 



Nonmagnetic < Olivine 52. 9i 



(Pyroxene 44. 9 Insoluble =44. 9 



Magnetic Nickeliferous iron 7.5 



A trace of manganese remains with the ferrous oxide; also a small amount of alumina. The trace of sodium is 

 sufficient to give a brilliant line in the spectroscope; the lithium line, while quite distinct, is not brilliant. 



A detailed account of the meteor was given in November of the same year by Leonard, 1 

 as follows: 



On the evening of February 12, 1875, at about half past 10 o'clock, a very large meteor was seen passing from 

 southwest to northeast over northern Missouri and southern Iowa, and coming to the earth in a shower of stones a few 

 miles east of Marengo, Iowa County, Iowa. At this hour the sky seems to have been quite clear over the greater part 

 of the States named, though light clouds and a sort of haze are spoken of by observers in the counties adjoining the 

 place where the stones fell, so that the meteor was seen throughout a region extending at least 400 miles in length 

 from southwest to northeast and 250 miles in breadth. In their descriptions of the course it pursued the accounts of 

 observers varied with their positions relative to the place where it fell. Those east of this region thought the course 

 to be toward the west or northwest, those north described it as moving toward the south or the southeast, and in a few 

 cases the statements of the different observers in the same town are contradictory as to the direction of its motion. 



The brilliancy of its light and the concussion which accompanied its fall were such as to attract very general 

 notice considering the lateness of the hour, and the observations herewith presented will be found to determine the 

 path it pursued with a fair degree of accuracy. At Keokuk, Iowa, it is described as: "Oblong in figure, with a train 

 ten to twelve times the length of the body, giving an intensely brilliant light, of crystalline whiteness at the center, 

 fire-red on the border, and throwing out red sparks and purplish jets of flame; train less luminous than the body; 

 exploded like a rocket. Opinions were divided as to whether any detonation accompanied the explosion." These 

 observations were collected by L. C. Ingersoll, M. D., from a number of persons in Keokuk who witnessed the flight. 



At Washington, Iowa, Rev. E. B. Taggart, in a letter to the Free Press of that city, describes it as of a "horse- 

 shoe shape, greatly elongated. The outer edge very bright, then a narrow dark space, with a core of intense bril- 

 liancy, so vivid as to blind the eyes for a moment. It had not a comet-like train, but a sort of following jacket of flame. 

 Detonations heard so violent as to shake the earth, and to jar the windows bike the shock of an earthquake." 



At Iowa Agricultural College, Professor Macomber says: "In form it was like an immense rocket with streamers 

 flowing from the hinder part, the front being smooth and curved like a saber. Its color was at first brilliant white, 

 illuminating the sky like a flash of lightning, then fading^gradually into yellow, then a deep rich orange, almost scarlet, 

 when it burst." 



At Sigourney, almost directly under the path of the meteor, Mr. J. A. Donnell, writing to the Sigourney News, 

 speaks of it as "a globe of fire with pale lines of light radiating from it. The light of the globe very vivid. It appeared 

 to be falling toward the earth from about 10° west of the zenith." He says he could see it dropping through a suc- 

 cession of clouds until it came inside the dome above him, where it apparently stood still for a moment and then 

 passed over toward the northeast. The detonation was compared to the discharge of a 40-gun battery which he had 

 heard in the army. 



At Amana, about 5 miles northeast of the middle region where the meteor fell, Mr. F. Christen says that "Its 

 light was at first dazzling white, then changed to red. Threw distinct shadows of objects on the street. Fragments 

 seemed to separate, not with violence, but simply as if falling apart; the separation was speedily followed by the dis- 

 appearance of the meteor." 



