1869.] 



Mineralogy. 



555 



for the most part, of iiickeliferous iron, chromite, and troilite. The 

 author gives his analyses of three meteorites, one of which fell at 

 Murcia, in Spain, on 24th Dec. 1858, and was exhibited in the 

 Paris Exhibition; the second fell at Tadjera, in the district of 

 Setif, Algiers, on the 9 th June, 1867, and is remarkable for the 

 absence of that crust, or varnish, which usually invests such stones; 

 whilst the third is a meteorite that fell on the 7th Sept. 1868, at 

 Sauguis-Saint-Etienne, in the departement of the Basses-Pyrenees. 

 To economize space, we place the analyses side by side, and give 

 only the mineralogical — not the chemical — composition. 



Silicates attacked by acids "I 



(oliviue) / 



Ditto not attacked (augite) 

 Nickeliferous iron 



Chromite 



Troilite 



In the class of metallic meteorites the general mass is not homo- 

 geneous, but consists of a number of alloys of iron and nickel, each 

 having a definite composition. Of these the most important are 

 tsenite, kamacite, plessite, and octibbehite. With these alloys are 

 associated certain carbides of iron, chiefly chalypite and campbeUite, 

 a sulphide of iron called troilite, a phosphide of iron and nickel 

 termed schreibersite, graphite or free carbon, and chrome iron-ore. 

 Certain stony grains are also occasionally present, and frequently 

 the surfaces are coated with a crust of oxidized matter. Add to 

 this the occluded gases sometimes met with — such as the hydrogen 

 found by Graham, and the nitrogen by Boussingault — and we have 

 what in the present state of our knowledge is a complete catalogue 

 of the constituents of meteoric irons. 



At about 6 o'clock in the evening of the 5th May, 1869, a 

 meteoric stone fell at Krahenberg, in the Bavarian Palatinate.* 

 It presented the form of a flattened spheroid, and weighed 31^ lbs. ; 

 its surface was covered with a black rind, and exhibited numerous 

 furrows. An account of this aerolite was read at the recent meeting 

 of the British Association. 



According to Dr. Sohncke, we can only hope to obtain an 

 insight into the nature of those recondite forces that produce 

 crystalline form, by determining with quantitative accuracy the 

 relative degrees of resistance which a crystal opposes in difl'erent 

 directions to the action of external mechanical forces. With this 

 view the learned Doctor has instituted a very elaborate series of 

 experiments on the manner in which the cohesion of rock-salt varies 



* Poggendorff's 'Annalen,' 5th May, 1869. 



