162 W. H. HOBBS REPEATING PATTERNS IN STRUCTURE OF LAND 



tions.^^ To the eastward of the dolomites the drainage betrays strikingly 

 the control by fractures which take especially the diagonal and the merid- 

 ional directions, as is true of the dolomites themselves (see figure 35).*'' 



THE AFRICAN FRACTURE SYSTEM 



Passarge in his great work Die Kalihari^^ has shown how "folds, faults, 

 and joints, with and without the pouring forth of eruptive rocks, follow 



in many cases definite 

 directions, which repeat 

 themselves many times, 

 and hence deserve spe- 

 cial names/^ These are : 

 (1) The Lombobo direc- 

 tion (north-south), (2) 

 the Cape direction- 

 (north 90 to 110 de- 

 grees east), (3) the Kaf- 

 fraria direction (north 

 40 to 60 degrees east), 

 and (4) the Damara 

 direction (north 35 de- 

 grees west). There are 

 represented, therefore, 

 two rectangular conju- 

 gate sets so oriented as 

 nearly to bisect each 

 other, as has been 

 shown above to be the 

 case for North America 

 and Europe. 

 In a valuable compilation and correlation of the voluminous but much 

 scattered scientific literature relating to the African continent. Simmer^'' 

 also has shown that the feature lines are very largely conditioned by frac- 



FlGURE 35, 



Showing the 



-Oriented Drainage of the Idrea River 



dominance of 

 directions. 



the diagonal 

 (After Stur) 



and meridional 



6« Karl Futterer : Durchbruchsthaler In den Siid-Alpen. Zeltsch. d. Ges. fur Erdkunde 

 BU Berlin, vol. 30, 1895, pp. 1-94, pis. 1-4. 



6'^ Dlomys Stur : II, Das Izonzothal von Flitsch abwarts bis Gorz, die Umgebungen 

 von Wlppach, Adelsberg, Planlna, und die V^'^ochein. Jahrb. d. k. k. geol. Relchsanst., 

 vol. 9, 1858, pp. 324-366, 1 pi. 



^^ Siegfried Passarge : Die Kallhari, Versuch einer physischgeographischen Darstellung 

 der Sandfelder des sudafrlkanlschen Beckens. Berlin, 1904, pp. 79-80 (C. Die Grund- 

 llnlen Im tektonischen Aufbau Siidafrlkas). 



^^ Hans Simmer : Der aktive Vulkanlsmus auf dem afrlkanlschen Festlande vmd den 

 afrlkanlschen Inseln. Gunther's Munchener Geographischer Studlen, No. 18, 1906, 

 p. 24. 



