18 CONTENTS. 



Chapter VII. — The Belt of Cementation — Continued. Pace 



Condition of -water in belt of cementation 566 



Amount of water in belt of cementation 569 



Circulation of water in belt of cementation 571 



Vigor of circulation 571 



Character of circulation 572 



Limiting formations 576 



Gravity 578 



Increase of temperature with depth 578 



Relative lengths of vertical and horizontal components 579 



Preferential use of large channels 580 



Resultant circulation 582 



General statement 589 



Temperature of entering and issuing water, and transfer of heat 589 



Variable materials and conditions of belt of cementation _ 594 



Work in belt of cementation 594 



Mechanical work 594 



Consolidation 595 



Strain within elastic limit 597 



Strain beyond elastic limit 599 



Chemical work 602 



Chemical changes 602 



Oxidation 604 



Carbonation 608 



Hydration 612 



Solution and deposition 612 



Quantitative relations between solution and deposition 61 3 



Resultant processes 617 



Cementation 617 



Cementing substances 621 



Oxides 622 



Silica 622 



Iron oxides 623 



Aluminum oxides 624 



Carbonates 624 



Calcite and dolomite 624 



Siderite 625 



Silicates 625 



Sulphides 627 



Distribution of elements in cementing minerals 627 



Distribution of cementing minerials 628 



Causes of cementation 629 



Expansion reactions 631 



Contributions from igneous rocks 634 



Selective precipitation 634 



Diffusion 636 



Conclusion 639 



