STUDY OF THE EMMET COUNTY METEORITE, THAT FELL NEAR ESTHERVILLE, EMMET COUNTY, IOWA, MAY 10, 1879. Amer. Jour. Science, xix, 1880, pp. 459-463. The fall of this meteorite is in all its attendant circumstances one of the most remarkable on record. I therefore visited the region, on my return to America some months after its fall, and saw the two large masses which are the main representatives. Several short notices have already appeared on the subject; among them, one each by Professor Shepard, Professor Peckham, and Professor Hinrichs; and in describing the physical and chemical characteristics of the original masses I shall be obliged to repeat some details that have been brought out. Locality. The place of fall is near Estherville, Emmet County, Iowa, just on the boundary of the State of Minnesota, latitude 43° 30', longitude 94° 50', within that region of the United States which has become remarkable for falls of meteorites, and of which I gave an outline map in my article on "The Three Meteorites that fell at Rochester in Indiana, Cynthiana in Kentucky, and Warrington in Missouri, within the space of one month.”* The State of Iowa has become particularly conspicuous in recent years as the landing place of these celestial messengers; and I now have under examination still another remarkable one with some peculiar physical characters, but about which I have not yet obtained the historic details. The phenomena accompanying the fall were of the usual character, but on a grander scale. It occurred about five o'clock in the afternoon, under a clear sky, with the sun shining brightly. In some places the meteorite was plainly visible in its passage through the air, and looked like a ball of fire with a long train of vapor or *See page 528. cloud of fire behind it; and one observer saw it one hundred miles from where it fell. Its course was from northwest to southeast. The sounds produced in its course are referred to as being "terrible" and "indescribable," as scaring cattle and terrifying the people over an area many miles in diameter. At first they were louder than that of the largest artillery; these were followed by a rumbling noise, as of a train of cars crossing a bridge. The concussion when it struck the ground was sensible to many persons, and it is reported that the soil was thrown into the air at the edge of a ravine where the largest of the masses was found. Two individuals were within two or three hundred yards of the spots where the two larger masses fell. There were distinctly two explosions. The first took place at a considerable height in the atmosphere, and several large fragments were projected to different points over an area of four square miles, the largest mass going farthest to the east. Another explosion occurred just before reaching the ground, and this accounts for the small fragments found near the largest mass. Impact with the earth.-A remarkable fact connected with the fall, besides that of the local disturbance of the earth alluded to, is the depth to which the mass penetrated. Had the fall taken place during the night, I doubt if the largest fragment would have been found. It struck within two hundred feet of a dwelling house, at a spot where there was a hole (previously made) six feet deep and over twelve feet in diameter, filled with water, and hav ing a bottom of stiff clay. This clay was excavated to a depth of eight feet before the meteorite was discovered, and two or three days elapsed before it was reached. Its total depth below the general surface of the ground was hence fourteen feet. The second large mass was found imbedded in blue clay about five feet below the surface, at a place two miles distant from the first. The third of the three largest masses was not discovered until the 23d of February, 1880, more than nine months after the fall, and its locality was four miles from the first. A trapper on the prairies, who had witnessed the original occurrence, observed a hole in a dried-up slough; on sounding it with his rat spear, he detected a hard body at the bottom, and on digging found the stone at a depth of five feet. Some small fragments were doubtless detached when the large mass approached the ground, as they were discovered near to it. The fragments thus far ob tained weighed respectively, 437, 170, 92, 28, 10, 4, and 2 pounds. Height and velocity.—A railroad engineer who observed it before the report, estimated its height to be forty miles, but at the time of the explosion much less; from an imperfect computation, he considered its velocity to be from two to four miles per second. External characters.-The masses are rough and knotted like large mulberry calculi, with rounded protuberances projecting from the surface on every side; the black coating is not uniform, being most marked between the projections. These projections have sometimes a bright metallic surface, showing them to consist of nodules of iron; and they also contain large lumps of an olivegreen mineral, having a distinct and easy cleavage, which is more distinct where the surface has been broken. The greater portion of the stony material is of a gray color, with this green mineral irregularly disseminated through it. The two minerals are mixed under various forms; sometimes the green mineral is in small rounded particles intimately mingled with the gray, at other times it is in small cavities in minute crystalline fragments, without any distinct faces, and almost colorless. The masses are quite heavy and vary much in specific gravity in their different parts; but the average can not be less than 4.5. When broken, one is immediately struck with the large nodules of metal among the gray and green stony substances, some of which will weigh one hundred grammes or more. In this respect this meteorite is unique, differing entirely from the mixed meteorites of Pallas, Atacama, etc., or the known meteoric stones rich in iron; for in none of these has the iron this nodular character. Another striking feature in the relation of the iron and stony matter is, that the larger nodules of iron appear to have shrunk away from the matrix; an elongated fissure of from one to three millimetres sometimes intervening, separating the matrix and nodules to the extent of one half the circumference of the latter, and appearing as if the iron had contracted from the stony matrix during the process of cooling. There are numerous small cavities of various sizes, where there are not any iron nodules, and where the minerals appear more crystalline, indicating an irregular shrinkage during the consolidation. The minerals. At first sight I expected to find more than two earthy minerals. The microscope gave, as with most meteoric stones, unsatisfactory results. I therefore tried to separate the stony minerals mechanically; the only mineral that I was enabled to obtain pure in sufficient quantity has an olive-green color, and occurs in masses of from one half to one inch in size, having an easy cleavage, especially in one direction; this is proved to be olivine. The same mineral occurs also in minute rounded concretions in other parts of the meteorite; and minute, almost colorless crystalline particles in the cavities I take to be olivine. Nickeliferous iron, as already stated, is very abundant. Troilite exists in small quantity. Chromite was also found. That the stony part of this meteorite consists essentially of bronzite and olivine will be seen from the chemical investigation, which found only three essential constituents, viz., silica, ferrous oxide, and magnesia. Another silicate will be referred to beyond, consisting of the same oxides, but in different proportions from either bronzite or olivine. Chemical constitution.-The stony part, pulverized and freed as far as possible from metallic iron by the aid of the magnet, when treated with chlorhydric acid on a water-bath for several hours, is resolved into soluble and insoluble parts, the proportions varying very much with different fragments, and ranging from sixteen to sixty per cent for the soluble part. This soluble part consists of silica, ferrous oxide, and magnesia, and without a trace of lime, thus indicating the absence of anorthite. 1. Insoluble portion.-The insoluble portion was carefully analyzed by fusion with carbonate of soda, and found to contain The oxygen ratio clearly indicates the mineral to be SiR, being virtually Si(MgFe), or the common form of bronzite contained in meteorites. 2. Soluble portion.-On testing the green mineral already referred to I found that this was the soluble portion, and it was readily detected in a pure state from the stony part of the meteorite. Its cleavage in one direction is very perfect; its specific gravity 3.35; hardness almost 7; pulverized, it is readily and completely decomposed by hydrochloric acid. Two analyses were made, one by decomposing it directly with hydrochloric acid over a water-bath, and the other by first fusing it with carbonate of soda-the two analyses agreeing perfectly. The above analysis gives the formula SiR2, or that of olivine. 3. Opalescent silicate.-In some parts of this meteorite, a silicate occurs that is opalescent, of a light greenish-yellow color, and cleaves readily. In one instance I observed it making a notable. projection on the surface. Although I had a number of fragments of the meteorite for examination, amounting to ten or twelve pounds, I did not obtain enough of the mineral to establish posi tively its true character, but I hope to obtain more. was made with about one hundred milligrammes of the eral with the following result: Silica.... Ferrous oxide. An analysis Oxygen ratio. Equivalent to SiŘ2+S12Ř, one atom of bronzite plus one atom of olivine, a form of silicate that we might expect to find in meteorites. 4. The nickeliferous iron.—As already stated this iron is abun dant in the meteorite, and sometimes in large nodules of fifty to one hundred grammes; on a polished surface the Widmannstättian figures are beautifully developed by acid. On analysis it was found to contain 5. Troilite. The proportion of troilite is not large, and it could be detached only in small fragments. 6. Chromite. When small pulverulent fragments of the meteorite are heated with hydrochloric acid for some time and the |