1274 



INDEX. 



Page. 



Placer deposits, metals derived from . . 1038 



sea-beach deposits so designated 1038 



Plagioclases, alterations and alteration products of. 374 

 Plagioclase feldspars, character, occurrence, forma- 

 tion, and alterations of 259-265 



Plants, abundance of, favorable to decomposition. 503-501 



chemical work of, in soils 453-456 



disintegrating effects of, on rocks - 444-447 



geological work of 504-506 



ground-water circulation affected by 417,422-423 



material abstracted from soil by _ 537-538 



sparseness of, favorable to rock disintegration 



without decomposition 500 



work of, in maintaining soils 505-506 



Plateau, J., on molecular attraction between water 



and walls of its container . . 144 



Pleonaste, chemical and physical constants of. 200 



Poiseuille, J., laws of water fiowage formulated 



by 139,140 



Polar regions, disintegration of rocks in 498-499 



Pore space of rocks, amount of 124-128 



form of openings constituting, diagrams show- 

 ing 132,133 



influence of amount of, on effects of freezing. .. 441 



size of openings constituting 134-146 



Porosity of rocks, effect of, as regards metamor- 



phism 40-41,641-642 



effect of, in cases of igneous intrusions 649-650 



influence of, on ore deposition 1201 



variations in 1200-1217 



Porphyritic chloritoid, thin section of 704 



Porphyritic minerals in rocks, development of... 699-705 



occurrence of , in schists, significance of 697 



Porphyritic schists, dissemination of 910-911 



Porphyritic textures, development of 699-705 



Portland mine, Cripple Creek, Colo., ground water 



in 1064-1065 



Posepny, P., on copper deposits of Australia. 1087 



on crustification _ 1134-1135 



on ore classification 1073 



on ore deposits, genesis of __ 1060, 



1065, 1076, 1128, 1160, 1181, 1235 

 on production of sulphide ores by ascending 



waters 1235 



Potash, percentage of, in grain and straw 454 



percentage of, in salts of sea water 942 



Potassa, amount of, in original and sedimentary 



rocks 1000 



See also Potassium carbonate; Potassium oxide. 



Potassium, in earth's crust. 934, 936, 999-1001 



inlithosphere-.-u 933,934 



in ocean 944 



in sea salt 943 



minerals and rocks containing 1000 



occurrence of 999-1002 



Potassium-bearing minerals, deposition of _ 627 



Potassium carbonate, chemical composition of and 



other data concerning 20(3 



Potassium carbonate, quartz, and diaspore, altera- 

 tion products of 382,407 



Potassium carbonate, gibbsite and quartz, altera- 

 tion products of 383,407 



Potassium carbonate, quartz, and corundum, altera- 

 tion products of 381,408 



Potassium feldspar, equation showing production of 



kaolin from 1070 



Potassium minerals, order of decomposition of, in 



rock weathering 536 



Page. 



Potassium oxide, in earth's crust _ 934, 937, 938 



in salts of sea water 942 



Potassium sulphate in the ocean _ 943 



Potassium sulphide in salts of sea water 943 



Potentialized energy resulting from strain, discus- 

 sion of ... 96-97 



Potsdam sandstone, ground water in, rate of flow 



of 585-586,587 



Potter, W. B., on preservation of original structure 



in decomposed rocks _ 526 



Powell, J. "W., on fourfold structural character of 



the earth 31 



on proportion of run-off to rainfall 414 



on springs of Grand Canyon of the Colorado 411 



on temperature required for aqueo-igneous fu- 

 sion 729 



Pratt, J. H., onchromite ores 1047 



Precht, H., on amounts of magnesium salts mined 



atStassfurt 994 



Precipitates, organic, formation of 792-793 



Precipitation, ascending waters favorable to 115,116 



by change of pressure, phenomena of 114-115 



by change of temperature, phenomena of 79-81, 



115-116 

 by reactions between aqueous solutions, phe- 

 nomena of 116-119 



by reactions between aqueous solutions and 



gases, phenomena of... 119 



conditions governing 116-118 



cycles of, influence of on ground-water level . . . 424 



heat effect in 105-106 



laws of 116-123 



likeness of , to freezing 113 



of abundant compounds in a solution, law of _ . . 539 



of cementing material, principles of. 629 



of material in belt of weathering, discussion 



of 539-554 



of metals, methods of 1081-1088 



of minerals from solutions, causes of 1078 



ores f ormed by 1037 



phenomena of 113-123 



selective, discussion of _. 634-636 



supersaturation necessary to , 113-114 



Prehnite, alterations and alteration products of ... 324, 



374,390,404 



chemical and physical constants of 200,324 



occurrence of 324 



sourcesand modes of formation of. 260, 263, 324, a33, 334, 

 335, 371, 376, 377, 386, 387, 388, 391, 401, 404, 625 

 Pressure, decrease of, precipitation of metals 



by 1081-1082 



effect of, on chemical reactions 100-104, 168 



on crystallization 103 



on metamorphism by igneous intrusion 652 



on ore deposition 1073,1074 



on production of minerals 363- 365 



on solution 77-78,101 



importance of, in chemical work in belt of weath- 

 ering 460-461 



increase of, effect of, on chemical reactions 89 



of gases, importance of, in metamorphism 70-71 



osmotic, character of 72-74 



precipitation by change of 114-115 



range of, at which work of water solutions is 



done 603 



relation of, to rapidity of deformation of rocks. 741 



to solubility. 77-79 



See also Strain; Stress. 



