Parent-Rock of the Diamond in South Africa. 95 



The general conclusions of the paper may be stated 

 thus : 



That the extreme depth of the lake is about one hun- 

 dred feet. 



That the temperature of the bottom is 42^ F., and that 

 the fall in the temperature between thirty feet and the 

 bottom is twenty-seven and a half degrees, most of this 

 fall taking place between thirty feet and forty-five feet. 



That the primary cause of the lake was probably a 

 widened fault in the Trenton limestone, the same force 

 giving rise at the same time, no doubt, to subterranean 

 crevices beneath, extending over a wide area, and enabling 

 distant waters to gradually find a passage to the lake. 



That the source of the waters of the lake is to be looked 

 for in the higher limestone area to the north eastward of 

 the Grand Trunk Railway as it passes through the 

 counties of Frontenac and Addington. 





(In view of the present situation in South Africa, the following 

 article will be found especially interesting, — apart from the inherent 

 scientific value of the paper. ) 



The Parent-Rock of the Diamond in South 

 Africa.^ 



By Professor T. G. Bo.vxey, D.Sc, LL.D., V.P.R.S. 



So much has been written on the occurrence of dia- 

 monds in South Africa that a very few w^ords may suffice 

 as preface to this communication. Eeferences to many 

 papers on the subject are given in " The Genesis and 

 Matrix of the Diamond" (1897), by the late Professor 

 H. Carvill Lewis,^ and others have been published since 



1 A Paper read before the Royal Society, June 1, 1S99. 



2 Edited by the present writer. 



