72 Dr. Walter Flight — History of Meteorites. 



be rhombic. It has a specific gravity of 3*42 and the following 

 composition : 



Oxygen. 

 Silicic acid 54-51 ... 29-07 



Iron protoxide 17-53 ... 3-89 



Manganese protoxide ... 0-29 ... - 06 



Magnesia 26-43 ... 10-57 



Lime 1-04 . ... 0-30 



Alumina 1-26 ... 0-59 



14-82 



101-06 



or that of a bronzite of the form (fFeOfMgO)Si0 8 . 



The pale grey very friable interstitial matter, freed as thoroughly 

 as possible from the grains of bronzite, was next examined. The 

 specific gravity is 340, and the mean composition of two analyses is 

 as follows : 



Silicic acid 



54-47 



Iron protoxide ... 

 Manganese protoxide ... 



17-15 

 0-28 



M agnesia 

 Lime 



26-12 

 1-39 



Alumina 



1-06 



Oxygen. 



29-05 

 3-81 

 006 



10-45 

 0-40 

 0-50 



14-72 



100-47 



It is seen, then, that the interstitial mineral and the grains have 

 the same composition, and that the constitution of the Ibbenbiihren 

 meteorite is one of the simplest of any meteorite yet investigated. 

 It not only consists essentially of a single silicate, but contains 

 neither chromite, magnetic pyrites, nor sulphur compound of any 

 kind. A trace of metallic iron was met with, and some reddish- 

 yellow grains with a brilliant surface, which have not been ex- 

 amined. Can they be the curious mineral found in the stone of 

 Busti, which appears to be a compound of zirconium (or titanium), 

 calcium, and sulphur ? The black crust is strongly magnetic, some 

 of the iron protoxide of the bronzite having been converted during 

 the passage of the stone through the atmosphere into the higher 

 and magnetic oxide. 



While this meteorite very nearly resembles that of Manegaum, it 

 approaches still more closely in composition to the bronzite of the 

 Shalka stone. It will be remarked that the meteoric bronzites far 

 exceed terrestrial bronzites as regards their per-centage of iron oxide. 



We now know four aerolites consisting of a single silicate : 

 Chassigny (1815, October 3rd) Olivine. 



Enstatite. 

 | Bronzite. 



Bishopville (1843, March 25th) 



Manegaum (1843, June 29th) 



Ibbenbiihren (1870, 17th June) 



Vom Eath's paper is illustrated with a drawing of the stone. 



In a short supplement in Poggendorjfs Annalen is given a brief 

 description of a microscopic section of this stone, prepared by 

 Buchner, of Giessen. The entire slice is seen to be made up of 

 rounded bronzite grains, without any heterogeneous ground mass unit- 

 ing them. By rotating the Nicols the most brilliant play of colours is 



