378 J. D. Dana — Archcean axes of Eastern J¥. America. 



minerals and sulphohalite, 3Na 2 S0 4 , 2NaCl ; Caracolite Na 2 S0 4 , 

 Pb[OH]Cl and Kainite MgS0 3 , KC1, 3H 2 are the only min- 

 eral occurrences of sulphate and chloride in combination. The 

 occurrence of small quantities of alumina in a copper mineral, 

 although not unknown, is certainly very unusual. It is also 

 interesting to note that the alumina in the formula, one atom, 

 is just sufficient to satisfy the quantivalence of the total acids 

 [A1C1]S0 4 , leaving six molecules of cupric oxide basic. 



Before closing the author desires to express the hope that 

 some one living in the neighborhood of Tombstone, Arizona, 

 will take an interest in examining both the collections and ores 

 of that region so as to secure, if possible, an abundant supply of 

 this mineral. 



Mineralogical Laboratory of the Sheffield Scientific School, 

 New Haven, March, 1890. 



Art. XLVII. — Archcean axes of Eastern North America', by 



James D. Dana. 



In my paper read before the Geological Society of America 

 at its Toronto meeting in August last, and since published by 

 the Society, after speaking of the Archaean range or series of 

 ridges along the course of the Appalachian Chain from Canada 

 through Vermont to Georgia as the Appalachian protaxis, I 

 briefly mentioned the parallel ranges east of the protaxis in 

 New England and Canada, and referred to the geological im- 

 portance of the included troughs or basins. I return to the 

 subject to make some additional explanations. 



The Appalachian protaxis, the earliest line of heights in the 

 history of the mountain chain, extends, with interruptions, 

 after a long course between the New England boundary and 

 the river St. Lawrence, through the eastern half of Vermont, 

 eastern Berkshire, northwestern Connecticut, Putnam, Orange 

 and Rockland counties in New York, northwestern New Jer- 

 sey, South Mountain in eastern Pennsylvania, and thence south- 

 westward through Virginia and beyond to South Carolina and 

 Georgia — in all over 1250 miles. The parallel eastern ranges, 

 having a general N.E.-S.W. trend, are continued into New- 

 foundland, range succeeding range quite to the farthest ex- 

 tremity of this great continental promontory. These ranges, 

 it should be understood, like that of the protaxis, are not sim- 

 ple continuous lines, but broken lines, with often parallel sub- 

 divisions, they having the composite style of all mountain 



ranges. 



