CONTENTS 
Page. 
Letter of transmittal, by George F. Becker ._ . 9 
Introduction 11 
The average composition of rocks 14 
Analyses 22 
Igneous and crystalline rocks 22 
Maine 22 
1. Kocks from Aroostook County 22 
2. Litchfieldite and associated minerals 24 
New Hampshire 26 
Vermont 26 
1. Rocks of Mount Ascutney 26 
2. Miscellaneous rocks ' 30 
Massachusetts 31 
1. Magnesian rocks 31 
2. Amphibolite 34 
3. Miscellaneous rocks 37 
Connecticut 42 
New York 44 
1. Rocks of the Adirondack region '. 44 
2. Miscellaneous rocks 46 
New Jersey 47 
Pennsylvania 48 
Delaware 49 
Maryland, District of Columbia 50 
1 . Peridotite and py roxenite 50 
2. Gabbro and diorite 52 
3. Granite and gneiss 54 
4. Miscellaneous rocks 59 
Virginia 61 
North Carolina 62 
Georgia 65 
Kentucky 66 
1. Elliott County dike. 66 
2. Crittenden County dike 68 
Tennessee 69 
Missouri 69 
Arkansas 70 
Texas 70 
Lake Superior region 76 
1 . Marquette region, Michigan 76 
2. Crystal Falls district, Michigan 78 
3 
