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ALBERT V. G. JAMES 



the floor. The upper surface rapidly parts with its heat by air 

 convection currents and convection along the vertical joints. Heat 

 is only slowly lost from the bottom surface because convection in 



Fig. 8. — "The Organ Pipes." These basaltic columns are 102' high and are 

 found on Jackson's Creek, Sydenham, Australia. 



'js^fy '•vJ-.n^''. 



I lA 



^^Si'tSmS^s^ . -^-'-- - - vC*S^'-.Ai*^-«r ^ *>> ^ 



Fig. 9. — Chisel structure. Several basaltic columns are shown with character- 

 istic horizontal banding. In each band the chisel structure can be seen. ("Organ 

 Pipes," Sydenham, Australia.) 



