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



lOI 



where no quarry is known to be near except the porcel- 

 lanite outcrop (Weston's Quarry) near Pontville, the 

 percentage of hornstone reaches the highest figure, and 

 that, though a porcellanite quarry was handy, the per- 

 centage of that rock is not more than 11.8 per cent, of 

 the total. This seems to prove more than anything the 

 preference for the hornstone. 



To me all this seems to show that though the horn- 

 stone was by far the most valued rock, and if possible 

 was used in preference to any other, porcellanite and 

 breccia were made use of only when the supply of horn- 

 stone was not ample. 



Now, if we compare 'how many specimens would be 

 lighter, equal, and heavier to flint, according to the 

 above figures for the frequency of occurrence we find 

 that 



In comparing this table with that on page 15, it 

 seems at the first glance that there is a great discrepancy 

 T^etween the ratio of lighter, equal, and heavier than 

 flint. It must be borne in mind that the 53 specimens 

 whose specific gravity was determined were not selected 

 ■according to the proper ratio of occurrence. In order 

 to bring the two tables in harmony I ought to have 

 •ascertained the specific gravity of 78 hornstones, 12 por- 

 cellanite, 5 breccia, and 5 others, or at the reduced 

 ratio of say 16 — 3 — i — i, while the actual determination 

 was made at the ratio of 



Hornstone. Porcellanite. Breccia. Others. 

 .2 III 



