370 Maury — Calcium Carlonate ConGretionanj Growth, 



Pure concretions like that at Hermon, differing from the 

 surrounding rock, are characteristic of shales. The fact that 

 the Malmesburj shales contain a low percentage of lime might 

 seem an objection to this theory of the concretionary origin of 

 the lime dome they inclose, but Professor R. B. Young of the 

 Johannesburg School of Mines assures me that his observations 

 have shown that particles may segregate from astonishingly 

 great distances. 



The slickensided plane of contact between the Hermon dome 

 and the Malmesbury shales is also v-ery suggestive of the con- 

 cretionary orig^in of the dome, since Professor Harris tells me 

 that this is commonly seen in the case of concretions in the 

 Southern States. The pressure causing the motion is appar- 

 ently chieily due to the increasing bulk of the growing con- 

 cretion. 



At Piquetberg, north of Hermon, is what may be a similar 

 dome, but Mr. Dahse had not then exploited it. In the vicinity 

 of Worcester, Cape Province, are a number of lime deposits, 

 but they lack the purity of the Hermon deposit and their ori- 

 gin is doubtless different. 



In conclusion, the writer believes that the Hermon deposit 

 represents a dome of calcium carbonate formed by the segre- 

 gation and crystallization of lime particles from the surround- 

 ing and underlying Malmesbury shales, and corresponds in its 

 mode of origin to the sodium chloride domes of Southern 

 Louisiana and Texas, and the conical "salt mountains" of Rhang 

 el Melah, Ain Hadjera and Djebel el Melah in Algeria. 



Hastings-on-Hudson, N. Y. 



