Sept. 6, 1888] 



NATURE 



457 



(8) The crust or varnish. This has been found to be due 

 entirely to the oxidation of the metal. The formula of the crust 

 of the Toluca meteorite is Fe 2 3 (FeNi)0, according to Meunier. 



The quantities of occluded gases vary considerably. Hydro- 

 gen is the first to come out when a vacuum is produced, and in 

 the cold — that is, when the tube containing the meteorite is not 

 heated. 



Thus, Graham found in the Lenarto meteorite, and in a 

 comparative experiment with clean horse-shoe nails made of 

 iron : — 1 



Mallet subsequently found in the meteorite picked up in 

 Augusta County — 2 



Dr. A. Wright subsequently determined the composition of 

 the gases given off at different temperatures, using the Iowa 

 meteorite. The results were as follows : — 



Nitrogen 



As regards the so-called occluded gases, iron and stony meteor 

 ites, according to Wright, show a marked distinction. While 

 the gases of the Lenarto iron contained 85-68 per cent, of 

 hydrogen, those obtained from cosmical masses of the stony kind, 

 such as the Iowa meteorite, are characterized by the presence of 

 carbonic acid, which constitutes nine-tenths of the gas evolved 

 at the temperature of boiling water, and about one -half of that 

 given off at a low red heat. 



This view of Wright's 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 hydro- 

 gen 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. 3 



In the siderites, the iron varies from 80 to 98 per cent., and 

 the nickel from 6 to 10 per cent. Sometimes the nickel is found 

 in larger quantities, as in the iron of d'Octibbeha Co., Mississipi, 

 found in the year 1854, which contained as much as 59 per cent., 

 while the iron was only 37 per cent. 



There is a singular circumstance connected with the varnish of 

 stony meteorites which was observed by Reinsch in the meteorite 

 of Krahenberg. The grains of metallic iron and troilite con- 

 tained in the varnish show no signs of oxidation. In the meteorite 

 of Morbihan, also, grains of nickel-iron project not only through 

 the smooth inner but also the rough outer crust. It has been 

 suggested that the surface of these meteorites was vitrified before 

 it entered our air, or at all events those lower strata of it in 

 which oxygen is abundant. 4 



In many cases minute chemical analysis has been most useful 

 in showing that meteorites which have been found in different 

 localities really belong to the same fall. 



Prof. Nordenskjold, on examining the Stalldalen meteorites 

 (Sweden, June 28, 1876), found that they resembled some eight 

 or nine others which he had before examined, although they 

 were entirely unconnected as regards their date of appearance ; 

 and that together they would form a well-marked group, but 

 which, he observes, will probably be found to be only one 

 among many similar groups of aerolites which will hereafter be 

 detected. 



The following short table brings together in a compact form 

 the chief substances met with in meteorites. It will indicate the 



1 Graham, "Chemical and Physical Researches," p. 283. 



2 Chemical News, June 21, 1872. 



3 Flight, op. cit p. 80. 



4 Flight, Geol. Mag., January 1875. 



(B) Carbonaceous 



Non-chondritic- 



cause of the continued reference to the speetra of magnesium 

 iron, and manganese in what follows. 



Siderites. 



Nickel-iron, manganese, copper. 



Troilite = FeS. 



Graphite. 



Schreibersite = iron and nickel phos- 

 phide, with which magnesium is- 

 always associated. 



Daubreelite = iron and chromium 

 sulphide. 



Siderolites. 



.. Olivine = chrysolite = peridot = 

 (MgFe) 2 4 Si = Si0 2 41-3, MgO 

 50-9, FeO 7-7. 



Enstatite Mg0 3 Si = Si0 2 60, MgO 

 40. 



Bronzite = enstatite, in which some 

 magnesium is replaced by iron. 



Nickel-iron, manganese. 



Troilite. 



Chromite = iron protoxide 32, 

 chromium sesquioxide 68, + alu- 

 minium and magnesium. 



Augite = pyroxene, Si0 2 55, CaO 

 23, MgO 16, MnO 0*5, FeO 4. 



Silicate of calcium, sodium, and 

 aluminium. 



Carbon in combination with H and O. 



Sulphates of Mg, Ca, Na, and K. 



Troilite. 



Olivine. 



Enstatite. 



Bronzite. 



Augite. 



Anorthite 



Spectral Analysis. 



It is imperative that we should know what spectroscopic 

 phenomena are presented by meteorites when they are exposed 

 to temperatures either high or low, such that luminous effects 

 are produced, however the heat which is associated with 

 luminosity is caused. 



To this end a great many investigations have been made, and 

 one method of investigation has been the following. 



A small portion of any particular meteorite, or still better 

 some dust or filings is inserted in an end-on tube, which is 

 placed in front of a spectroscope, so that a spectroscopic record 

 of the luminosity may be obtained. The tube is at the same 

 time attached to a Sprengel pump, so that in this way a vacuum 

 can be obtained, and is supplied with poles, so that an electric 

 current can be sent through it. Supposing that such bodies as 

 meteorites exist in free space, we must understand that they 

 exist practically in a vacuum, so that it is a fair thing to begin 

 the laboratory work by getting as nearly a vacuum as possible. 

 The next thing to do is to try the effect of the lowest tem- 

 perature, and for that purpose the central part of the tube 

 containing the little fragments is heated by a Bunsen burner. 



If any effect is produced by this application of heat it will 

 after some little time be evidenced by the commencement of a 

 spectrum or by some change in the pre-existing one. What has 

 been found is that there is scarcely any meteorite which can be 

 examined in this way which does not give off a sufficient quantity 

 of hydrogen to allow the hydrogen spectrum, when a feeble 

 electric current is made to travel along the tube, to be very 

 beautifully visible. 



If the temperature of the meteoric particles is kept sufficiently 

 low, we see practically the spectrum of hydrogen alone. That 

 is a demonstration of the very well known fact that with those 

 bodies generally acknowledged to enter into the composition of 

 meteorites, hydrogen is always associated. 



If under these same conditions the temperature is increased, 

 the spectrum of carbon begins to be visible, indicating that 

 associated with the hydrogen there is some compound or com- 



