Cl CO 
vill 
CONTENTS. 
Page. 
Origin and composition of trap,. 83 
Trap dykes compared with mineral 
veins,. 83 
2. Porphyry,. 84 
Nature, origin and period of formation 
of porphyry,. 85 
Varieties of porphyry,. 86 
3. Magnetic oxide of iron,. 87 
Geological position of the magnetic 
oxide of iron,. 88 
Original formation of masses of ore,. 90 
Veins, their structure, etc.*. 91 
4. Specular oxide of iron,. 92 
Geological position of the specular 
oxide, . 92 
Serpentine breccia,. 96 
Topographical position of the specular 
oxide,. 96 
Origin of the magnetic and specular 
oxides of iron,. 97 
CHAPTER V. 
New-York Transition system,. 99 
Sedimentary rocks of the northern coun¬ 
ties; lithological characters; fossils; dif¬ 
ferent members of the group; thick¬ 
ness of the whole mass,. *.... 99 
Champlain group, . 102 
1. Potsdam sandstone,. 102 
. Calciferous sandrock, . 105 
. Chazy limestone,. 107 
4. Birdseye limestone,. 107 
Black marble of Isle la Motte,. 110 
5. Trenton limestone,. 112 
6. Utica slate,. 116 
Equivalent of the Utica slate in the Si¬ 
lurian system,. 118 
7. Loraine shales,. 119 
Varieties, . 121 
8. Grey sandstone,. 123 
Varieties, .. 124 
P.AGE. 
CHAPTER VI. 
Tertiary, its name, lithological character, 
arrangement, fossils, era of deposition, 
and thickness,. 127 
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, . 137 
General strike and dip,. 141 
CHAPTER VHI. 
Rocks composing the Taconic system, their 
order of superposition, and their general 
strike and dip,. 144 
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 Berkshire,. 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 account 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 
