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This figure shows a combination of forms sometimes observed on the silicate Scapolite, with the unit pyramid, (o); the prisms of the first and second orders, (M) and (b) respectively; and the pyramid of the third order, (s).

Scapolite

This figure shows a combination of forms sometimes observed on the silicate Scapolite, with the unit…

This crystal of Calcium Phosphate, Apatite, represents a complex combination of hexagonal hemihedral forms produced by the pyramidal selection. The nine forms comprise the basal pinacoid ,(P); the prism of the first order, (M); second order, (u); and third order, (h); three pyramids of the first order, (r), (x), and (y); one pyramid of the second order, (s); and one of the third order, (m).

Calcium Phosphate, Apatite

This crystal of Calcium Phosphate, Apatite, represents a complex combination of hexagonal hemihedral…

This is a crystal of Copper Silicate (Dioptase) with a rhombohedron of the third order, (s), in combination with the prism of the second order, (m), and the negative rhombohedron, (r). This crystal is an example of rhombohedral tetartohedrism in the hexagonal system.

Copper Silicate Showing Rhombohedral Tetartohedrism In the Hexagonal System

This is a crystal of Copper Silicate (Dioptase) with a rhombohedron of the third order, (s), in combination…

This crystal is mainly terminated by a rhombohedron of the third order, (x). With this form are associated the prisms of the first and the second order, (m) and (a); another rhombohedron of the third order, (s), and the two rhombohedrons of the first order, (r).

Phenacite

This crystal is mainly terminated by a rhombohedron of the third order, (x). With this form are associated…

This crystal of Tourmaline exhibits hemimorphism in the direction of the vertical axis. Its forms are the prisms, (g), which as a result of hemimorphism, appear as a trigonal prism, and (a); the scalenohedron, (s), and the two rhombohedrons, (R) and (r), at the antilogue pole, while only (R) occurs at the analogue pole.

Tourmaline

This crystal of Tourmaline exhibits hemimorphism in the direction of the vertical axis. Its forms are…

This is an orthorhombic crystal of olivine. It is formed by the orthorhombic prism in combination with two pinacoids.

Orthorhombic Crystal of Olivine

This is an orthorhombic crystal of olivine. It is formed by the orthorhombic prism in combination with…

This form shows the fundamental prism (p) on a crystal of topaz, in combination with another prism, (p'); the basal pinacoid, (c); the brachydome, (g); and the four pyramids, (o), (o'), (o''), and (x).

Orthorhombic Crystal of Topaz

This form shows the fundamental prism (p) on a crystal of topaz, in combination with another prism,…

This figure shows two twin rhombohedrons, symmetrical with reference to a prism of the first order, but without any composition face. There is a complete interpenetration of their substance, and the space common to both is very irregularly distributed between them, as may be shown by an examination in polarized light.

Twin Rhombohedrons

This figure shows two twin rhombohedrons, symmetrical with reference to a prism of the first order,…

This crystal of Aragonite shows a method of twinning where the twinning plane may change its direction, as when the two symmetrical faces of a prism successively serve as twinning planes.

Cyclic Twinning

This crystal of Aragonite shows a method of twinning where the twinning plane may change its direction,…

The tetragonal rutile grows upon the rhombohedral titanic iron, so that its prism of the second order, ∞ P ∞ (100), coincides with the basal pinacoid of the latter mineral, while its vertical axis has the direction of one of the intermediate lateral axes of the iron ore.

Rutile Growing Upon Titanic Iron

The tetragonal rutile grows upon the rhombohedral titanic iron, so that its prism of the second order,…

This image shows one of Friedrich Froebel's divided cube (this one divided into many smaller cubes and prisms). Froebel's cubes were used to encourage creativity in kindergarten-age children. The children could rearrange the smaller shapes into combinations that showed life, knowledge, and beauty.

Froebel's Divided Cube (Complex)

This image shows one of Friedrich Froebel's divided cube (this one divided into many smaller cubes and…

These Hargrave box kites are named so after their inventor, Lawrence Hargrave of Sydney. These kites generally have two rectangular cells covered with nainsook cloth, except at the top and bottom, and one is secured above the other by four or more sticks. Some of these kites stand 9 ft. high, have 70 sq. ft. of lifting surface, and weigh only eleven pounds.The kites can be flown singly or in tandem.

Hargrave Kite

These Hargrave box kites are named so after their inventor, Lawrence Hargrave of Sydney. These kites…

Changing from polar to rectangular coordinates.

Rectangular Coordinates

Changing from polar to rectangular coordinates.

Transforming from one set of rectangular axes to another with the same origin, but different direction.

Rectangular Axes

Transforming from one set of rectangular axes to another with the same origin, but different direction.

"An instrument used chiefly to measure the angular deviation of light rays in passing through a prism, and hence to determine the refractive indices of the substance of which the prism is formed." &mdashWhitney;, 1889

Spectrometer

"An instrument used chiefly to measure the angular deviation of light rays in passing through a prism,…

"...a tube with a slit at the further end through which the light enters, and at the other end a collimating lens which brings the rays into a parallel beam (the slit is formed between two parallel edges the distance between which can be varied at will)..." —Whitney, 1889

Prism Spectroscope from the Late 19th Century

"...a tube with a slit at the further end through which the light enters, and at the other end a collimating…

"...an instrument which gives a spectrum when the source of the light is in a straight line with the eye—that is, which gives dispersion without deviation—is called a direct vision spectroscope..." —Whitney, 1889

Direct Vision Spectroscope

"...an instrument which gives a spectrum when the source of the light is in a straight line with the…

This divider has leaves and small round kernels featured in a design on the sides. The center area has rays coming out from a blank, rectangular center. It can be used as a divider or banner.

Divider with Leaves and Sun Rays

This divider has leaves and small round kernels featured in a design on the sides. The center area has…