THE CONVEX SURFACE 101 



tings and is there also deeply furrowed in directions nearly radial. The 

 lobate side recedes in more gradual curves, is marked by small and 

 irregularly distributed pittings, and is covered with a thin film of oxide. 

 Through this coating of oxide the nearly radial furrows and ridges 

 which characterize the opposite margin can be followed without difficulty, 

 though they are much less distinct, and the effect produced is altogether 

 like that which would be expected if this side had lain in a moist soil 

 while the other had received greater protection. The margin not covered 

 by the oxide (that of the shallow pittings) shows a steely, metallic luster. 

 Near the ends of the front the surface resembles that of the margin where 

 the shallow pittings are found. The end opposite the saw section, how- 

 ever, projects to the front from the margin of the central boss before its 

 surface recedes in the regular curves characteristic of other parts of the 

 front (see plate 6, figure 1). This suggests that the meteorite may have 

 been bent in about its geometric center by a force acting normal, to its 

 surface. 



The central boss of the front shows even under the lens little trace of 

 the radial furrows, and then only in circumferential portions. On the 

 straighter side, where the surface slopes away rapidly from this boss, 

 the furrows begin with great distinctness at the line where the flat boss 

 gives place to the backward slope. 



Drift ridges and furrows. — The radial markings could perhaps better 

 be described as ridges than as furrows ; they are in reality the material 

 left in sharp, knife-edge lines between very shallow furrows having 

 nearly flat bottoms. The ridges have a basal thickness of a fifth to a 

 tenth of a millimeter, and where best developed the intervening furrows 

 widen from about a millimeter at the margin of the central boss to two 

 millimeters at the present circumference of the meteorite. Approxi- 

 mating to right lines the ridges appear to have been modified in their 

 direction to some extent by the crystalline structure of the meteorite, 

 but even where deviated from their initial direction the tendency to 

 maintain rectilinear directions is apparent. They sometimes cross one 

 another at extremely acute angles (see plate 5). Interesting radial drift 

 phenomena have been described by Tschermak and Doll on the meteor- 

 ite from Mocs.* 



While at first sight the ridges would appear to be strictly radial, 

 closer examination, especially when made by stretching a fine thread 

 along them, reveals the fact that they are in reality slightly curved in a 



♦Tschermak : Ueber die Meteoriten von Mocs. Sitzungesber. Akad. Wissensch., Wien., vol. 85, 

 1882, p. 195. 



Doll: Zwiei neue Kriterien fiir die Orientirung der Meteoriten. Jahrb. d. k. k. geol. Reich- 

 sanst., vol. xxxvii, 1887, pi. vi. 



