XXXVl 
TABLE OF CONTENTS. 
Page, 
(F) . List of minerals observed in Orange county by Dr. W. Horton.'577 
Opinions of Dr. Horton on superposition, age, etc. 580 
(G) . Diary of the geological survey of New-York island by Prof. L. D. Gale. 681 
Examinations on 10th avenue. 581 
9th avenue. 585 
8th “ 586 
7th, 6th and 5th avenues. 591 
4th avenue. 592 
3d « 594 
2d “ 596 
North part of the island. 599 
Statistics and other details. 602 
Building materials. 602 
Manure. 602 
Borings for water. 603 
CHAPTER X. 
DIP AND STRIKE OF ROCKS, AND GENERAL INFERENCES FROM FACTS, 605 
1. Axes of elevation. 605 
Strike and dip, tables of. 606, 622 
Transverse axes of elevation. 622 
Longitudinal axes of elevation. 623 
2. Joints and veins. 625, 626 
Table of joints. 625 
Causes of joints unlmown. 626 
Queries. 626 
3. Ages of rocks, and periods of elevation and of metamorphic agency. 626 
(A) . Ages of the rocks. 626, 628 
(B) . Periods of elevation and disturbance. 628, 629 
(C) . Periods of metamorphic agency. 629, 631 
4. Causes of disturbances and change of characters considered. 631 
Additional cause of tangential force suggested. 631 
Cause a general one. 631 
Analysis of this cause. 632 
Phenomena of physical geology referred to three causes. 632 
Effect of a change in the day on longitude. 632 
Either secular or paroxysmal. 633 
Effects the same but varied in quantity. 633 
Day not varied for 2,000 years... 633 
Geological evidence of variation at more distant periods. 633 
Effects of almost inappreciable changes. 633 
Subject for investigation by mathematicians. 633 
