1885.] 40 J IFrazer. 



Note 6. The following is an analysis by Dr. Genth of the Trap 

 (Dolerite) clyke, which crosses Beeler's farm two miles S. "W. of York. 



P. C. 



Silicic oxide 52.53 



Phosphoric oxide 0.15 



Titanic oxide 0. 32 



Alumina 14.35 



Ferric oxide 5.93 



Ferrous oxide 5.45 



Manganous oxide (trace) 



Magnesia 7.99 



Lime 10.27 



Lithia (faintest trace) 



Soda 1.87 



Potash 0.92 



Copper (t race) 



Sulphur 0.08 



Ignition 1-23 



101.04 



By a mineralogical analysis of the results (C, p. 123 &) it appears that 

 there are two molecules of labradorite and one of pyroxene which to- 

 gether essentially make up this rock. 



Note 7. In a volume entitled " The Azoic system and its proposed sub- 

 divisons," by J. D. Whitney and M. E. Wadsworth, printed as a Bulletin 

 of the Museum of Comparative Zoology at Harvard College in August, 

 1884, but which might well serve as a type of all that a scientific memoir 

 ought not to be, the authors are pleased to dispose of the work on the 

 Archaean rocks of this State as if it were entirely due to four persons 

 representing all grades of experience, and various dates of activity from 

 1858 to 1880. The two elder and better known of the lour are waved 

 aside osfensibly because they are unreliable, in that they have modified 

 their views, or did not feel justified in drawing sharp divisions on the 

 map which were supported only by a high degree of probability. The 

 younger and less generally known of these, though nowhere claiming 

 to have solved the problem of sequence, are given a prominence which 

 contrasts strangely with their own modest words. The mystery is, how- 

 ever, explained when we observe that the views of Prof. Rogers and Dr. 

 Hunt do not accord with those of the authors of the volume, whereas Mr. 

 Charles E. Hall leans towards the view that the mica schists of the Phila- 

 delphia group, the South Valley Hill rocks, &c, are well within, if not 

 high up in the Palaeozoic column ; and Prof. Prime's merit in the eyes 

 of these authors appears to be that he has differed with Dr. Hunt as 

 to the age of the rocks in a certain mine in Berks county. The 



PROC. AMER. PHILOS. SOC. XXIII. 123. 2z. PRINTED JUNE 11, 1886. 



