GH. SZ. GH*. T. (? radiant elongated). Clark, 1872. Denning, 1876. Confirmed GH*. Dn. 148°, +2°. Denning, 1876. GH* (=Ga of 1867 B.A. Atlas G. & H.) gives swift S. (41°,+12° and 57°,+12°.) Clark at 59°, +1°. SZ. 3. For Gruber's observations on October Meteor-showers, see Brit. Assoc. Report, vol. 1875, pp. 220-223. Prof. A. S. Herschel's comet accordances with meteoric showers at page 229, ibid. Note.-Mr. Denning has lately furnished Mr. Greg with well-determined meteor epochs and radiants, deduced chiefly from his own recent and from IV. AEROLITES. Several falls of meteorites (one of them of much importance) have recently occurred, detailed accounts of which, and of recent researches on aërolites and on aërolitic meteors, have been collected during the past year by Dr. Flight, and form in this Appendix (see Part II.) a continuation of the similar abstracts contained in last year's Report. PART I.-A Review of recent Stonefalls and of Papers relating to Meteorites. By A. S. HERSCHEL. The following falls of meteorites have been placed on record since the date of the last of those which were there described : A.D. 1814, Gurramconda, near Chittoor, North Arcot, Madras, 1875, Sept. 14, 4" P.M. Supino, circ. Frosinone, Italy. 1876, Apr. 20, 3h 40m P.M. Rowton, near Wellington, Salop, England (Ironfall). 1876, June 28, 11h-12h A.M. Ställdalen, Dalecarlia, Sweden. (See account of this aerolite at the end of this Appendix.) The following descriptions have also been given of meteoric appearances, presumably aërolitic, of which no further corroborations have hitherto been received. 1875, Feb. 10th, Isle d'Oléron, and March 9th, Orleans, France. (See these Reports, vol. for 1875, p. 206.) In the French weekly scientific journal Les Mondes,' vol. xxxvi. p. 458 (March 25th, 1875), these meteors are described as falls of aërolites. It appears probable from this description that they were detonating fireballs; but of this, and of their possible aërolitic characters, no other evidence has been produced of which the Committee has yet received intelligence. The following notice of large meteors seen in America in December and January last, by Mr. C. W. Irish, of Iowa City, U.S., although affirming them to have both been of the detonating class, does not distinctly pronounce them to have been accompanied by falls of aërolites; but one at least of these fireballs produced a very loud explosion. "In the last week (the 27th) of December, 1875, at 9h P.M., and also in the first week of January, 1876, large meteors traversed the air near the south boundary of this (Iowa) State. One passed near Ringold Co., south-easterly; the other passed over St. Joseph, in the State of Missouri, travelling eastwards; and both came to the earth, I think, very brilliant and noisy. It is stated, in the Kansas Chief' of December 30th, that after a lapse of 2 minutes after the disappearance of the meteor of the 27th, a sound like the discharge of a heavy cannon was heard, or rather one loud explosion followed by a lighter one. It jarred houses and rattled windows." 6 From the Scientific American' of August 12th, 1876 (p. 98), Mr. Wood communicates the following apparently authentic record of a recent fall of an aërolite in Kentucky, U.S., no meteor, however, being described, and no other details of the occurrence having yet been received:-"The Louisville' Courier Journal' states that on July 18th (1876), at 4" A.M., Mr. White, watchman of the Whiteford engine-house, whilst on duty, was startled by a loud report, like that of a pistol, and instantly following some heavy substance fell into the street a few feet distant. Mr. White searched, and found imbedded in the ground a stone of the appearance of dark flint, weighing about two pounds. The stone was broken to pieces, and examined during the day by several scientific gentlemen, who pronounced it genuine meteoric substance. The probable solution is that the explosion occurred at a greater distance than was supposed, and that this was but a small fragment of a large aërolite." To the many valuable essays on the physical characters of aërolites with which Professor Maskelyne has from time to time enlarged the extent of our knowledge of the real nature of these bodies, and to the unremitting zeal with which he has collected in the British Museum a series of authentic specimens of meteorites not excelled in any other national mineralogical collection, we owe many of the most interesting discoveries and conclusions of scientific importance regarding the probable history of meteorites which have been arrived at in recent years. Some outline of the progress that has been made in these investigations was given in the concluding paragraphs of last year's Report; but a very valuable summary of the existing state of knowledge on the composition, structure, and probable history of meteorites has appeared in a series of papers*, published during the past year by Professor Maskelyne, entitled "Some Lecture Notes on Meteorites," to which, as they contain a most instructive review of the many points of information accumulated during a prolonged period of successful and diligent research, the Committee has especial satisfaction (while noticing in this Report the principal contributions to aërolitic science during the past year, notable additions to which were made in our own country) in being able to refer. These useful Lecture Notes contain in a few condensed and readily accessible pages the mature results of almost numberless scattered treatises and memoirs ; and besides the certain basis of instruction which they offer on the ordinary features of composition, structure, and typical characters of meteorites, and of the circumstances which attend their fall, a store of useful hints and germs of future theories are thrown out regarding the extra-terrestrial conditions of rock-formation on distant astronomical bodies from which these strange fragments are derived. In connexion with the discoveries (and especially with the views advanced by Mr. Lockyer to explain them) of the spectroscope regarding the selective arrangement and definite elevations of certain elements forming the ordinary ingredients of terrestrial rocks in the outer layers of the sun's atmosphere, the low degree of oxidation which invariably characterizes the constituent minerals of meteorites appears, among the conjectures to which Professor Maskelyne draws attention, no longer to be a singular peculiarity of the parent bodies from which they were projected, but a condition. of their surfaces which corresponds exactly with the common assumption of their small dimensions, usually regarded as a necessary supposition to account for the projection and liberation of aerolites from the attraction of those distant spheres by forces of ordinary eruptive violence. Such views of the arrangement and concentration of the elements by gravity in condensing cosmical masses, tending, in the order of superposition of their densities, to eliminate as much oxygen and other light-atomed elements as they contain towards the surfaces, if, as appears very probable, they should soon be confirmed by a more perfectly discriminating scrutiny of the sun's atmosphere with the spectroscope, will link together more closely than before the evidence. which the spectroscope affords, and which has independently been gathered * 'Nature,' vol. xii. pp. 485, 504, 520 (September 30 and October 7, 14, 1875). from a minute examination of meteorites, that the materials and the laws of aggregation of the elementary substances constituting the largest and the smallest suns and planets are essentially the same, only differing very strikingly from each other in their scale. Conditions which we notice on the sun and on our own globe we may regard as having in all probability once presided over the process of condensation of every planet from a state of vapour, and as having notably collected on the surfaces of the small meteorite-yielding planetoids, in exact proportion to their size, less oxygen than we find existing on the surface of the earth. Passing over many valuable pages of descriptive matter in the Notes,' containing exact accounts and appropriate discussions of many new as well as formerly narrated particulars and observations, it should be stated that the explanation given in one of the first paragraphs of the first article in Nature' (loco sup. cit. p. 487) of the characteristic pittings of the surfaces of meteoric stones and irons, supposing them to arise from exfoliation of pieces of the stone or iron by the sudden expansion of the material produced by heat, is set aside in a later paper by Professor Maskelyne in favour of a far more natural and more probable hypothesis, the leading points of which will be presently described. The meteoric fall of the greatest interest during the past year was that of an aërosiderite, or piece of metallic iron, which fell in Shropshire, eight or ten miles north of the Wrekin, on the 20th of April, 1876. Rain was falling heavily, unaccompanied by lightning or thunder, and the sky was thickly overcast for some time before and after the hour, 3h 40m P.M., when the event took place. At that time a strange rumbling noise was heard, followed by a startling explosion like a discharge of heavy artillery, audible over an area several miles in extent among the neighbouring villages of Shropshire. The meteorite was found about an hour after this occurrence by the tenant of a grass field, near the town of Wellington, Mr. Brooks, who had occasion to visit the spot, and observing the ground to have been disturbed, probed the hole which the meteorite had made, and discovered it at a depth of 18 inches below the surface. Some men at work at no great distance had heard the noise of its descent, but without being able to indicate the exact place or its direction. The hole was nearly perpendicular, the meteorite having entered the ground almost vertically in a north-west to south-easterly direction, and when found it was still quite warm. It weighs 73 lbs., and is a mass of metallic iron irregularly angular, although all its edges appear to have been rounded by fusion in its transit through the air, and, except at the point where it first struck the ground, it is covered with a thin black pellicle of the magnetic oxide of iron. The surface is somewhat pitted or marked with slight depressions, one of which occurring in a fissure of the mass affords some instructive evidence of the causes of their formation. The exposed metallic part of the surface exhibits crystalline structure very clearly when it is etched. The meteorite was first exhibited publicly at a local bazaar, held in Wolverhampton, and afterwards at a meeting of the Natural History Society of Birmingham, by whose representations to the agent of the Duke of Cleveland, and by the Duke's consent, in whose property it fell, it was presented to the British Museum. It is only the seventh aerosiderite, or meteoric iron, of which the fall has been witnessed*, although upwards of a hundred iron masses have been discovered in different parts of the globe, which are un * For a list of the earlier known examples of such ironfalls, see these Reports (vol. for 1875, p. 246). doubtedly meteoric, and two such have been found in Great Britain. The falls of eight stony meteorites have been recorded in this country, of which the last happened at Killeter, in Ireland, on the 29th of April, 1844. A Section of the Rowton siderite for analysis will shortly be made; and the foregoing description of the meteorite, and of the circumstances attending its fall, are extracted from an account of the occurrence of the aerosiderite by Professor Maskelyne, in Nature' of July 27th, 1876 (vol. xiv. p. 472). Regarding the origin of the remarkable pittings of the surfaces of aerolites and aërosiderites, an opinion was lately expressed and advocated by Daubrée that in their flight through the air they undergo erosion and excavation by joint effects of fusion and combustion, assisted mainly by air vortices attacking most violently certain portions of their surface. An important paper on this subject, by Professor Maskelyne, was published more recently in the Philosophical Magazine' of August 1876. It is true that pittings identical in appearance with those of meteorites are found on the surfaces of certain large grains of powder blown unconsumed from the mouths of the large modern rifled ordnance (excellent specimens of this kind received from Professor Abel and Major Noble having been shown by Professor Maskelyne to Mr. Daubrée in the summer of 1875); but two important grounds for exception, in regard to this explanation, are pointed out by Professor Maskelyne, which must not be overlooked. The closest examination of the molten glaze with which, like other parts of their surfaces, the pittings or depressions of meteorites are coated over, shows no indications of vorticose action of the air, although stream-lines of the glaze from front to rear are of frequent and conspicuous occurrence. The process of atmospheric combination, or combustion, is also rare, if not entirely absent, during the period of most intense operation of the heat, as is shown by particles of metallic iron which are occasionally found imbedded in the glaze, and even by cases where the highly oxidizable mineral Oldhamite (calcium sulphide), occurring in spherules in the Bustee meteorite, is glazed over equally with the Augite, without offering any signs of combustion or of the production of cavities where they are exposed. On the other hand, the readier fusibility of some constituent minerals of meteorites appears to determine the formation of depressions of the surface where they present themselves; and among the magnesian silicates which form the principal materials of stony meteorites, it appears that the more ferruginous varieties are somewhat more fusible than the more purely magnesiferous silicates, which, with minor assemblages of other minerals, enter, in very various proportions, into the composition of the stony masses of acrolites. If the entire process of surface-melting and abstraction which meteorites undergo is thus correctly represented, the question of the amount of fracture and division into separate parts which they may suffer by their collision with the atmosphere is one which is yet undecided; and many difficulties beset the inquiry if meteorites are single bodies, or if, as numerous examples appear to testify, they sometimes enter the atmosphere in swarms. An important dissertation on this question by F. Mohr appeared during the past year in Liebig's Annalen't; and a paper by Von Tschermak (of which a brief abstract was presented in last year's Report), on the same subject of the probable origin and of the original forms of aërolites, is now translated in extenso in the Supplementary No. for June 1876 of the Philosophical Magazine.' 6 *Comptes Rendus,' April 24th, 1876. |