1 84 STUDIES FOR STUDENTS 



never characterize an entire mass, so far as I am aware, but 

 only portions, and occasionally but a small portion of a single 

 mass. The amount of curvature is not great, rarely if ever 

 exceeding io mm in 50. A single plate never has more than one 

 direction of curvature, though it is often straight for some dis- 

 tance at one end and curved at the other. With reference to 

 each other, however, the directions of curvature of individual 

 plates may be quite different. Like faults, the bending is 

 referred by Brezina to the result of the impact of the meteorite 

 upon the earth. 



Veins {Adern, Filons, Veines). — These occur in many stony 

 meteorites, in fact in a sufficient number to characterize seven 

 of the thirty-seven groups into which Brezina divides stony 

 meteorites. The veins may vary in width from a mere line to 

 19 millimeters (Mocs). An even greater dimension is indicated 

 by the size of single stones from the Pultusk and Mocs showers, 

 which seem to be of a substance like that of the veins. The 

 veins penetrate the stones now in a nearly straight direction and 

 now in a more or less tortuous one. Sometimes they are single, 

 then again branched, and again ramify to such an extent as to 

 form a network. They are rarely uniform in width for any 

 appreciable distance. On the contrary, they widen and narrow 

 very irregularly, often forking so as to enclose portions of the 

 mass and then meeting again. The Bluff meteorite shows two 

 systems of veins crossing one another at angles of about 45 . 

 The narrower of these is uniform in width and was observed 

 over a plane 4X15 inches in extent. The wider varies much in 

 width and is less extensive. 



In color, veins are dark, usually black. The substance 

 filling them is black, opaque, brittle, and of a semi-glassy char- 

 acter. In polarized light it appears amorphous and isotropic. 

 It often includes splinters of the adjoining stone and little 

 spheres of nickel-iron and troilite. Along the walls are often 

 seen delicate metallic foliae, lying parallel to the direction of 

 the veins. These appear in cross section like delicate threads. 

 From the nickel-iron grains threads often run out in a direction 



