CONTENTS. 
Pace 
Part I. Origin, Composition, and Structure of Slate 5 
Definition and classification 5 
Origin 6 
Petrographic characters 9 
History of research 9 
Spotted slates 15 
Igneous slates 18 
Structure 18 
Bedding 18 
Slaty cleavage 22 
Slip cleavage ( "false cleavage " ) 24 
Grain 25 
Joints 27 
Faults 29 
Shear zones (hogbacks) 29 
Cleavage bands 31 
Veins 32 
Nodules 33 
Dikes '. 33 
Geological relations 34 
Chemistry of slate 34 
Chemical composition 34 
Chemical changes in weathering 37 
Chemical composition of New York and Vermont slates 39 
Economic geology of slate , 42 
Difficulties in slate quarrying 42 
Bedding and cleavage — how distinguished 42 
' ' Flints " — their nature and cause . 43 
Relations of joints, dikes, and shear zones 44 
Use of geological map and compass in prospecting for slate 44 
Methods of testing slate 45 
Technical description of a slate quarry 50 
Part II. Slate Deposits of the United States 51 
Arizona 51 
Arkansas 51 
California 56 
Georgia 59 
Maine 60 
Maryland 67 
Minnesota 70 
New Jersey 70 
New York 70 
Pennsylvania 75 
Pennsylvania and Maryland ( Peach Bottom ) 85 
Tennessee 88 
Utah '. 89 
Vermont 89 
Virginia Ill 
West Virginia 119 
3 
