VIU 



CONTENTS. 



Pace. 

 83 



83 



84 



Orifrin and composition of trap, 



Trap dykes compared with mineral 

 veins, 



2. Porphyry, " * 



Nature, origin and period of formation 



of porphyry, 



Varieties of porphyry, 



3. Magnetic oxide of iron, •- ' 



Geological position of the magnetic 



oxide of iron, 



Original formation of masses of ore, . 

 Veins, their structure, etc. • 



4. Specular oxide of iron, 



Geological position of the specular 

 oxide, 



Serpentine breccia, ^^ 



Topographical position of the specular 

 oSde, 56 



Origin of the magnetic and specular 

 oxides of iron, -' ' 



85 

 8G 



88 

 90 

 91 

 92 



92 



CHAPTER V, 



99 



99 

 102 



New- York Transition system, 



Sedimentary rocks of the northern coun- 

 ties; lithological characters; fossils; dif- 

 ferent members of the group; thick- 

 ness of the whole mass, 



Champlain group, 



1. Potsdam sandstone, '02 



2. Calciferous sandrock, 105 



3. Chazy limestone, 107 



4. Birdseye limestone, • • • 107 



Black marble of Isle la Motto, 110 



Trenton limestone, 1 12 



Utica slate, 1 16 



Equivalent of the Utica slate in the Si- 

 lurian system, 118 



7. Lorainc shales, 119 



Varieties, 1-1 



8. Grey sandstone, 123 



Varieties 124 



5. 

 6. 



CHAPTER VI. 



Tertiary, its name, lithological character, 

 arrangement, fossils, era of deposition, 



and thickness, ^^' 



Denudations of the tertiary, 128 



Extent of the tertiary of Lake Champlain, 130 

 Geological reasoning founded upon the 

 tertiary under consideration, 133 



CHAPTER VII. 



Taconic system, its name and extent, 135 



Position and relations of the Taconic sys- 

 tem, ^^^ 



General strike and dip, 141 



CHAPTER VIII. 



Rocks composing the Taconic system, their 

 order of superposition, and their general 

 strike and dip, 1^4 



CHAPTER IX. 



Individual rocks of the Taconic system, their 

 characters, mineral products, and ab- 

 sence of fossils, 150 



1. Sparry limestone, 151 



2. Magnesian slate, 152 



3. Stockbridge limestone, 154 



Valleys of Berksliire, 156 



4. Granular quartz, 158 



Mineral products of the slates and lime- 

 stones of the Taconic system, .... 161 

 Conclusion of the Taconic system, .. 163 



CHAPTER X. 

 Geographical geology, or an accoimt of the 

 rocks of each county in the Second Geo- 

 logical District, 165 



General remarks, 165 



Warren COUNTY, 170 



Ranges of mountains, 170 



Lakes, water courses, valleys, drainage, 171 



Granite, , 173 



Primitive limestone, 175 



