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PART II.-Accounts of Aerolites and Aërolitic Meteors, and Abstracts of recent Researches on them. By W. FLIGHT.

1875, February 12th, 10.30 г.M. (Chicago time).-Iowa Co., State of Iowa*.

The conclusions arrived at by Wright, on examining the gases occluded by the iron of these meteorites, have been referred to in the Report (B.A.) for 1875, p. 240. He considered that the stony meteorites were distinguished from the iron ones by having the oxides of carbon, chiefly the dioxide, as their characteristic gases instead of hydrogen. This theory has been called in question by Mallet, who refers to his examination of the gases of the iron of Augusta Co., Virginia, where the ratio of the oxides of carbon to hydrogen is 4:3, and to his having pointed out in 1872 that hydrogen could no longer be regarded as the characteristic gaseous ingredient of meteoric iron. In his paper of that date he stated that although it might be assumed that carbonic oxide would be the original form in which the gaseous carbon-compounds existed in the iron, and that it broke up at the temperature of the experiment into carbon retained by the iron and into carbonic acid, yet in view of the steady decrease of the quantity of the latter gas which was evolved as the experiment proceeded, it seems more likely that a larger amount of carbon originally existed in the higher state of oxidation. Mallet considers that, when all the circumstances of the experiment are considered in each case, Wright's conclusion cannot be sustained.

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In a paper dated some months later, Wright replies to Mallet's criticism. He states that he only meant this expression of opinion to be tentative, but that the results of further work completely justify the conclusion at which he had arrived. He has re-examined the gases of the iron of this meteorite, and examined those of the iron of some other stony meteorites, such as Ohio, Pultusk, Parnallee, and Weston, and finds that not only do the stony metcorites give off a much larger volume of gas at low temperatures, but the composition of the gas in all the cases studied is quite different from that evolved from meteoric iron. In no case among the results obtained with the alloy is the amount of carbonic acid greater than 20 per cent. at 500°, than 15 per cent. of the whole quantity evolved, while in every case but one the volume of carbonic oxide is considerably larger. In the chondritic meteorites, on the other hand, the percentage of the latter gas is conspicuously small, while the carbonic acid constitutes more than half the total gas evolved below a red heat, except in the case of the meteorite under consideration which fell at Iowa, and here the percentage is not much less, especially if we reject the numbers representing the amount obtained by a second and longcontinued application of a red heat. At a temperature of about 350° it constitutes from 80 to 90 per cent. of the gaseous products, and at 90° it forms more than 90 per cent. of the gas evolved. The hydrogen, on the other hand, progressively increases in quantity with the rise of temperature, and is the most important constituent of the first portions removed at a red heat. The form in which the carbonic acid is occluded is a problem which he cannot at present solve. That it is actually absorbed appears to be certain.

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* J. W. Mallet, Amer. Journ. Sc.' 1875, vol. x. p. 206; N. R. Leonard, ib. vol. x. p. 357; A. W. Wright, Amer. Journ. Sc.' 1876, vol. xi. p. 253; "An Account of the Detonating Meteor of February 12, 1875," by C. W. Irish, Iowa City, 1875, Daily Press Job Printing Office, Dubuque Street; M. Delafontaine, Bibliothèque Universelle,' October 1875, p. 188; G. A. Daubrée, L'Institut,' 1875 (Nos. 105-122), p. 138; C. W. Gümbel, 'Sitzungsber. Ak. Wiss. München,' 1875, vol. v. p. 313,

That it has been taken up from the atmosphere has been proposed. He finds, however, that the iron of the Iowa meteorite contains no more carbonic acid now than it did at the time of its fall.

Leonard gives a detailed account of the appearance presented by the meteor, which is stated to have been seen throughout a region 400 miles from S.W. to N.E., and 250 miles in breadth. The stones vary in weight from a few ounces to 74 lbs., and the aggregate weight is 500 lbs. ; the area over which they were scattered appears to be 7 miles in length, and 4 miles at its greatest breadth. A plan of the townships included in this area is given in Leonard's paper, and it shows where the chief stones fell. By reason of the frozen condition of the ground at the time of the fall, and the low angle of descent, it appears probable that almost all the fragments which fell have been secured. The velocity of the meteor has not been satisfactorily determined; it appears probable that during the last 60 or 70 miles of its course it travelled at the rate of from 6 to 7 miles per second.

An interesting pamphlet by Mr. Irish, C.E., deals with the appearance presented by the meteor. He has incorporated in his paper a number of letters received from observers stationed over a wide area, describing their impressions as to its altitude, velocity, and appearance; and he has given a drawing of the meteor, and prepared a map of the district, showing the projection of its path through the air. I learn by a recent letter from Mr. Irish that two blocks, one weighing 72 lbs., the other 48 lbs., which evidently formed one and the same mass which was disrupted during the descent, have since been found; and the aggregate weight of the stones now collected cannot be less than 700 lbs. I am also indebted to Mr. Irish for six excellent photographs of the Iowa stones, sixty-seven in number, which form the collections of Prof. Hinrichs, Mr. J. P. Irish, and himself. They were taken by Mr. Thomas James, of Iowa city, and are in the very best style of photographic art.

Prof. Gümbel, of Munich, has recently published an interesting paper on the characters of this meteorite. He finds the crust to possess a deep bottlegreen or brownish-red colour, and to possess in polarized light all the characters of an amorphous glass-like mass. When a fragment is heated it turns of a dark brown colour, like that noticed by him in the eruptive rocks of the Fichtelgebirg, and he regards this change as a safe indication of the presence of olivine.

The composition of the stone is found to be:

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The silicate decomposed by acid is an olivine, having the formula.

2 (MgO, FeO), SiO,; and the insoluble silicate, which has been regarded

by Dr. Lawrence Smith as pyroxene, gave the oxygen ratios-silicic acid = 29.68; bases = 10.29. It appears not improbable that in this case the silicate was not completely decomposed during analysis.

The paper is illustrated with an interesting plate of a microscopic section showing olivine, augite, meteoric iron, chromite, troilite, particles of a reddish hue which resemble garnet but which doubly refract light and exhibit optical characters which will not allow of their being identified with nosean, and chondra showing fibrous, radiate, and granular structure, as well as others

which evidently consist of olivine, and some which are opaque and finely granular. The meteoric iron has a hackly angular structure, and has the appearance which it would present if reduced to the metallic state in the position which it at present occupies.

1875, December 27th, 9 P.M.- -Kansas.

I have to thank Mr. Irish, C.E., of Iowa City, for two cuttings from newspapers (the Kansas Chief of December 30th, and the Kansas Evening Post of December 29th) recording the fall of a detonating meteor of the above date. It traversed the heavens in a direction from N.W. to S.E., leaving a lurid streak in its wake. The whole heavens were lighted up, and "made all out of doors almost as light as full moonlight." The meteor was of the usual whitish-red colour, and when it exploded the fiery fragments were scattered in all directions. "Perhaps two minutes later, and after all appearance of the meteor had disappeared, the sound of the explosion came like the discharge of a heavy cannon; or rather one loud explosion, immediately followed by a lighter one like an echo. The explosion jarred houses and rattled windows. The size of the meteor and the terrible force of the explosion may be imagined from the fact that the distance was so great that it required about two minutes for the sound to reach the earth, and the concussion was so plainly felt and heard at that distance. The phenomenon was witnessed over a large extent of country." An observer, writing from Fort Leavenworth, states that it appeared to have its origin in the constellation Cassiopeia, and its course was due east. Mr. Irish states that he has made every effort to secure possession of the meteorites which must have fallen, but has been unsuccessful. The time of flight is estimated to have been from 12 to 15 seconds.

1875, December 27th, 9.20 P.M.-State of Missouri, U.S.A.

I am indebted to Mr. Irish, C.E., of Iowa City, for an interesting description of this detonating meteor, as well as for a map, on which he has traced its course. The point where it was first seen in the zenith is at Thayer, in Nebraska, near the borders of Kansas, and about 120 miles W. of the Missouri river. It was seen by him at Iowa City first as a small meteor, which rapidly became brighter, and was hidden from view when at an altitude of about 40° by a building; at this moment it gave out a very brilliant quivering flash of light, which illuminated the whole heavens. It appears from Mr. Irish's map to have been seen over a wide area, from Stillwater in Minnesota on the north, to Buffalo in Missouri on the south, and as far west as the shores of Lake Michigan. Near the termination of the flight sounds were heard: over Archer, in Nebraska, a rushing roaring sound, as of a mighty wind, was noticed; at St. Joseph, in Missouri, the first distinct explosion was remarked, and between that town and Livingstone Co. frequent and very heavy detonations occurred. In the last-mentioned district, and at places as far as 60 miles distant, numerous red fragments were seen to fall. He says, "I have had several persons looking for the meteorites where the fall must have taken place; but the whole district is covered with dense forest, and is mountainous and broken, and the ground was very soft from the long-continued rains preceding the fall, so that no fragments have been found. All the observers of the final explosion agree that the great bulk of the material was thrown upward and backward upon the course of the meteor, as the arrow-pointed dots in my sketch indicate. The luminous appearance continued in sight for

15 minutes."

As

D.E. 62

G.H.

97

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