BY FRITZ NOETLING, M.A., PH.D., ETC. gg 



SPECIFIC GRAVITY. 



If calculated in per cents, this table can be condensed 

 to a little one, particularly if we assume three groups of 

 specific gravity in comparison to flint, viz., lighter, equal, 

 and heavier than flint. We have then 



This table is of the greatest interest, because it 

 proves that the majority of the rocks used for the manu- 

 facture of the tronatta were considerably heavier than 

 flint, from which the European eolithes and arohaeo- 

 lithes were made. 



These figures will be more illustrative still if we 

 compare the ratio of frequency of the different kind of 

 Tocks used in the manufacture of tronatta. The follow- 

 ing figures are arranged according to localities: — 



