258 BULLETIN OF THE 



Walling, H. F. 



Some Indications of Recent Sensitiveness to Unequal Pressures in the 

 Earth's Crust. Amer. Assoc. Proc, XXVII., 1878, 190-197. 

 Whelpley, J. D. 



Trap and Sandstone of the Connecticut Valley, — Theory of their Relation. 

 Assoc. Amer. Geols. Proc, 1845, 61-64. 

 Wurtz, H. 



Progress of an Investigation of the Structure and Lithology of the Hudson 

 River Palisades. N. Y. Lyceum Proc, I., 1870-71, 99-105. 



3. OBSERVATIONS. 



The following observations were made in the summer of 1882. The 

 attempt has been made in recording them to keep inference distinct 

 from observed fact, though the two may come in the same sentence. 

 The observations have been reduced as far as possible to graphic form, 

 for ease of reading as well as for the convenience of those who may care 

 to repeat them. It should be remembered that they are mostly the 

 work of short excursions, made with the object of discovering the posi- 

 tion and condition of the rocks only at certain points, and not with any 

 idea of preparing complete geological maps of a district. The plans are 

 generally traced from topographical or geological maps ; none of the 

 sections are constructed accurately, but all are kept down near natural 

 proportions. In order to avoid too much assumption in these sec- 

 tions, all lines of contact not directly seen are drawn broken-dotted 



( ); the Hanging Hills section is an accidental exception to 



this rule. The scales of maps and sections are only approximate. The 

 observations are referred to in the text farther on by the letters at 

 their headings. 



Nomenclature. — The trap ranges are grouped according to Percival's 

 method : the largest of a system is called the wiam range; lateral ranges 

 on the outcrop side or face of the main range are called anterior; on the 

 back or dip side, posterior. These lateral ranges are numbered accord- 

 ing to their distance from the main range. In the case of overflows, 

 these terms have the unforeseen advantage of serving to denote the rela- 

 tive dates of eruption.^ Upper and lower contacts are between the trap 

 and the overlying and underlying sandstones. Dike (except in quota- 

 tions) is restricted to masses of igneous rock clearly of later date than the 

 rocks they intersect, and with a greater extension across the layers of 

 sandstone than parallel to them. Sheet is applied to interbedded masses 

 of trap, of intrusive or of overflow origin. Sandstone is sometimes used 



