Principal forms of the isometric system: octahedron.

Octahedron

Principal forms of the isometric system: octahedron.

A combination of octahedron and dodecahedron.

Octahedron and dodecahedron

A combination of octahedron and dodecahedron.

"Combiantion of pyritohedron and octahedron." — Ford, 1912

Octahedron and pyritohedron

"Combiantion of pyritohedron and octahedron." — Ford, 1912

"A combination of pyritohedron and octahedron." — Ford, 1912

Octahedron and pyritohedron

"A combination of pyritohedron and octahedron." — Ford, 1912

"A combination of a trisoctahedron and an octahedron. It will be noted that the faces of the trisoctahedron bevel the edges of the ocrahedron." — Ford, 1912

Octahedron and trisoctahedron

"A combination of a trisoctahedron and an octahedron. It will be noted that the faces of the trisoctahedron…

"When a corner or an edge of one form is replaced by a face of another form, the first is said to be trunctuated by the second." — Ford, 1912

Cube trunctuated by octahedron

"When a corner or an edge of one form is replaced by a face of another form, the first is said to be…

A distorted octahedron.

Distorted octahedron

A distorted octahedron.

"A contact twin, since the two individuals lie simply in contact with each other upon a certain plane." — Ford, 1912

Twinned octahedron

"A contact twin, since the two individuals lie simply in contact with each other upon a certain plane."…

A spring is a point where groundwater flows from the ground, and is thus where the aquifer surface meets the ground surface

Origin of Springs

A spring is a point where groundwater flows from the ground, and is thus where the aquifer surface meets…

"Unit orographic blocks in granite, near the knife works, Hotchkissville. a Area over downthrown block." -Walcott, 1901

Orographic Blocks

"Unit orographic blocks in granite, near the knife works, Hotchkissville. a Area over downthrown block."…

A mollusk radiate from the Paleozoic time, Orthis testudinaria.

Orthis Mollusk

A mollusk radiate from the Paleozoic time, Orthis testudinaria.

A mollusk radiate from the Paleozoic time, Orthis occidentalis.

Orthis Mollusk

A mollusk radiate from the Paleozoic time, Orthis occidentalis.

A mollusk radiate from the Paleozoic time, Orthis varica of the Niagara group.

Orthis Mollusk

A mollusk radiate from the Paleozoic time, Orthis varica of the Niagara group.

"Orthoceras, upper part showing perforated chamber." -Taylor, 1904

Orthoceras

"Orthoceras, upper part showing perforated chamber." -Taylor, 1904

A curved orthoceras, common in limestone (Cyrtoceras Murchisoni).

Curved Orthoceras

A curved orthoceras, common in limestone (Cyrtoceras Murchisoni).

Orthoclase

Orthoclase

Orthoclase

Orthoclase.

Orthoclase

Orthoclase.

"Monoclinic. Crystals are usually prismatic in habit and have as prominent forms, clinopinacoid, base, prism, with often smaller orthodomes." — Ford, 1912

Orthoclase

"Monoclinic. Crystals are usually prismatic in habit and have as prominent forms, clinopinacoid, base,…

"Monoclinic. Crystals are usually prismatic in habit and have as prominent forms, clinopinacoid, base, prism, with often smaller orthodomes." — Ford, 1912

Orthoclase

"Monoclinic. Crystals are usually prismatic in habit and have as prominent forms, clinopinacoid, base,…

"Monoclinic. Crystals are usually prismatic in habit and have as prominent forms, clinopinacoid, base, prism, with often smaller orthodomes." — Ford, 1912

Orthoclase

"Monoclinic. Crystals are usually prismatic in habit and have as prominent forms, clinopinacoid, base,…

"Outcrop showing faults, spur south of Deadwood." -Walcott, 1901

Outcrop

"Outcrop showing faults, spur south of Deadwood." -Walcott, 1901

"Diagram to illustrate crescentic offsetting of outcrops due to progressively increasing tilting of orographic blocks." -Walcott, 1901

Outcrop Diagram

"Diagram to illustrate crescentic offsetting of outcrops due to progressively increasing tilting of…

"Diagram to illustrate crescentic offsetting of outcrops due to progressively increasing throw of orgaraphic blocks." -Walcott, 1901

Outcrop Diagram

"Diagram to illustrate crescentic offsetting of outcrops due to progressively increasing throw of orgaraphic…

"Diagram to illustrate crescentic offsetting of outcrops due to progressive decrease in width of orographic blocks." -Walcott, 1901

Outcrop Diagram

"Diagram to illustrate crescentic offsetting of outcrops due to progressive decrease in width of orographic…

"Fish, trilobites, brachiopods, corals, and graptolites of the Palaeozoic epoch." -Taylor, 1904

Paleozoic Animals

"Fish, trilobites, brachiopods, corals, and graptolites of the Palaeozoic epoch." -Taylor, 1904

"Pentamerus Knightii." -Taylor, 1904

Pentamerus

"Pentamerus Knightii." -Taylor, 1904

When the outlet tube of the reservoir is siphon-shaped, the discharge of the spring becomes <em>periodical</em>. The spring continues to discharge its waters for a time, and then stops flowing, even during wet weather. After a certain interval it again charges. The times during which the spring continues to discharge are always practically the same. Hence the spring is called a periodical spring.

Periodical Spring

When the outlet tube of the reservoir is siphon-shaped, the discharge of the spring becomes periodical.…

"Microscopic Section of Pitchstone, showing dendritic crystals." -Taylor, 1904

Pitchstone

"Microscopic Section of Pitchstone, showing dendritic crystals." -Taylor, 1904

The great low plain of North America lies between the Atlantic system on the east and the Pacific system of the west.

Plains

The great low plain of North America lies between the Atlantic system on the east and the Pacific system…

"A crystal has a center of symmetry if an imaginary line is passed from some point on its surface through its center, and a similar point is found on the line at an equal distance beyond the center." &mdash; Ford, 1912

Symmetry plane

"A crystal has a center of symmetry if an imaginary line is passed from some point on its surface through…

A mollusk radiate from the Paleozoic time, Platyceras angulatum from the Niagara group.

Platyceras Mollusk

A mollusk radiate from the Paleozoic time, Platyceras angulatum from the Niagara group.

A Radiate Polyp coral, Dendrophyllia.

Polyp

A Radiate Polyp coral, Dendrophyllia.

A Radiate Polyp, an Actinia.

Radiate Polyp

A Radiate Polyp, an Actinia.

"Microscopic Section of artificial Porphyrine." -Taylor, 1904

Porphyrine

"Microscopic Section of artificial Porphyrine." -Taylor, 1904

"The dietetragonal prism is a form consisting of eight rectangular vertical faces, each of which intersects one horizontal crystallographic axis and is parallel to the other two axes." &mdash; Ford, 1912

Ditetragonal prism

"The dietetragonal prism is a form consisting of eight rectangular vertical faces, each of which intersects…

"The dihexagonal prism has twelve rectangular vertical faces, each of which intersects all three of the horizontal crystallographic axes at different lengths." &mdash; Ford, 1912

Dihexagonal prism

"The dihexagonal prism has twelve rectangular vertical faces, each of which intersects all three of…

"The prism of the first order consists of four rectangular vertical faces, each of which intersects the two horizontal crystallographic axes equally." &mdash; Ford, 1912

First order prism

"The prism of the first order consists of four rectangular vertical faces, each of which intersects…

"Crystal faces are described according to their relations to the crystallographic axes. A series of numbers which indicate the relative distances by which a face intersects the different axes are called its parameters." &mdash; Ford, 1912

Orthohombie prism

"Crystal faces are described according to their relations to the crystallographic axes. A series of…

"The prism of the second order consists of four rectangular vertical faces, each of which intersects one horizontal crystallographic axis and is parallel to the other two axes." &mdash; Ford, 1912

Second order prism

"The prism of the second order consists of four rectangular vertical faces, each of which intersects…

A mollusk radiate from the Paleozoic time, Pterinea emacerata from the Niagara group.

Pterinea Mollusk

A mollusk radiate from the Paleozoic time, Pterinea emacerata from the Niagara group.

"Huge fossil Crustacean (Pterygotus Anglicus). Old Red Sandstone, Forfarshire." -Taylor, 1904

Pterygotus anglicus

"Huge fossil Crustacean (Pterygotus Anglicus). Old Red Sandstone, Forfarshire." -Taylor, 1904

"An orthorhombic pyramid has eight triangular faces, each of which intersects all three of the crystallographic axes." &mdash; Ford, 1912

Pyramid

"An orthorhombic pyramid has eight triangular faces, each of which intersects all three of the crystallographic…

"The dihexagonal pyramid is a form of twenty-four isoceles triangular faces, each of which intersects all three of the horizontal axes differently and intersects also the vertical axis." &mdash; Ford, 1912

Dihexagonal pyramid

"The dihexagonal pyramid is a form of twenty-four isoceles triangular faces, each of which intersects…

"The ditetragonal pyramid is a form composed of sixteen isoceles trianglular faces, each of which intersects all three of the crystallographic axes, cutting the two horizontal axes at different lengths." &mdash; Ford, 1912

Ditetragonal pyramid

"The ditetragonal pyramid is a form composed of sixteen isoceles trianglular faces, each of which intersects…

"The pyramid of the first order is a form consisting of eight isoceles triangular faces, each of which interesects all three crystallographic axes, the intercepts upon the two horizontal axes being equal." &mdash; Ford, 1912

First order pyramid

"The pyramid of the first order is a form consisting of eight isoceles triangular faces, each of which…

"Crystal faces are described according to their relations to the crystallographic axes. A series of numbers which indicate the relative distances by which a face intersects the different axes are called its parameters." &mdash; Ford, 1912

Orthorhombie pyramid

"Crystal faces are described according to their relations to the crystallographic axes. A series of…

"The pyramid of the second order is a form composed of eight isoceles triangular faces, each of which intersects one horizontal axis and the vertical axis and is parallel to the second horizontal axis." &mdash; Ford, 1912

Second order pyramid

"The pyramid of the second order is a form composed of eight isoceles triangular faces, each of which…

"The symmetry of the Pyritohedral class is as follows: The three crystal axes of binary symmetry; the four diagonal axes, each of which emerges in the middle of the octant, are axes of trigonal symmetry." &mdash; Ford, 1912

Symmetry of pyritohedral class

"The symmetry of the Pyritohedral class is as follows: The three crystal axes of binary symmetry; the…

"This form consists of twelve pentagonal-shaped faces, each of which intersects one crystallographic axis at unity, the second axis at some multiple, and is parallel to the third." &mdash; Ford, 1912

Pyritohedron

"This form consists of twelve pentagonal-shaped faces, each of which intersects one crystallographic…

Principal forms of the isometric system: pyritohedron.

Pyritohedron

Principal forms of the isometric system: pyritohedron.

"A combination of pyritohedron and octahedron." &mdash; Ford, 1912

Pyritohedron and octahedron

"A combination of pyritohedron and octahedron." — Ford, 1912

"A cube trunctuated with pyritohedron and octahedron." &mdash; Ford, 1912

Pyritohedron, cube, and octahedron

"A cube trunctuated with pyritohedron and octahedron." — Ford, 1912

Pyroxene

Pyroxene

Pyroxene

Pyroxene

Pyroxene

Pyroxene

"Terminated usually by a combination of a positive and negative rhombohedron, which often are so equally developed as to give the effect of a hexagonal pyramid." &mdash; Ford, 1912

Quartz

"Terminated usually by a combination of a positive and negative rhombohedron, which often are so equally…

"Terminated usually by a combination of a positive and negative rhombohedron, which often are so equally developed as to give the effect of a hexagonal pyramid. Sometimes one rhombohedron predominates or occurs alone." &mdash; Ford, 1912

Quartz

"Terminated usually by a combination of a positive and negative rhombohedron, which often are so equally…

"Terminated usually by a combination of a positive and negative rhombohedron, which often are so equally developed as to give the effect of a hexagonal pyramid. Sometimes one rhombohedron predominates or occurs alone. At times the prism faces are wanting, and the combination of the two rhombodendrons gives what appears to be a doubly terminated hexagonal pyramid, known as a quartzoid." &mdash; Ford, 1912

Quartz

"Terminated usually by a combination of a positive and negative rhombohedron, which often are so equally…

Thin section of quartz sandstone shown under the microscope. The original rounded quartz grains are surrounded by new quartz, forming quartzite.

Quartz Sandstone

Thin section of quartz sandstone shown under the microscope. The original rounded quartz grains are…

"The quartz crystals are said to be right or left handed, depending upon whether these faces are to be observed trunctuating the edges between prism and rhombohedron." &mdash; Ford, 1912

Left-handed quartz

"The quartz crystals are said to be right or left handed, depending upon whether these faces are to…

"The quartz crystals are said to be right or left handed, depending upon whether these faces are to be observed trunctuating the edges between prism and rhombohedron." &mdash; Ford, 1912

Right-handed quartz

"The quartz crystals are said to be right or left handed, depending upon whether these faces are to…