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This figure shows two tetrahedrons with parallel axes, and symmetrically placed with reference to the faces of the cube. The example given is a tetrahedrite crystal.

Tetrahedrite

This figure shows two tetrahedrons with parallel axes, and symmetrically placed with reference to the…

Transformation of coordinates to new axes.

Transform Coordinates

Transformation of coordinates to new axes.

"One of the most important of astronomical instruments, consists of a telescope fixed to a horizontal axis, so as to revolve in the plane of the meridian, and is employed, as its name denotes, in the observation of the meridian transits of the heavenly bodies. The axis, which is the most important part of the instrument, and thus demands the utmost care in its construction, consists of a hollow sphere or cube, to opposite sides of which are tightly fastened the bases of two cones in whose apices the pivots are screwed; the sphere or cube is pierced for the admission of the telescope, which is firmly soldered at right angles to the axis." — Chambers, 1881

Transit Instrument

"One of the most important of astronomical instruments, consists of a telescope fixed to a horizontal…

"The wheel and axle consists of two cylinders of different diameters, rigidly connected, so that they turn together about a common axis." — Hallock, 1905

Wheel and Axle

"The wheel and axle consists of two cylinders of different diameters, rigidly connected, so that they…

"Considered as a lever, the fulcrum is at the common axis, while the arms of the lever are the radii of the wheel and of the axle. The usual arrangement is to take ac, the radius of the wheel, as the power arm, and bc , the radius of the axle, as the weight arm." -Avery 1895

Wheel and Axle

"Considered as a lever, the fulcrum is at the common axis, while the arms of the lever are the radii…

"The whole length of the tube of the wheel barometer, from C to A, is 34 or 35 inches, and it is filled with mercury, as usual. The mercury rises in the short leg to the point a, where there is a small piece of glass floating on its surface, to which there is attached a silk string, passing over the pulley p. To the axis of the pulley is fixed an index, or hand, and behind this is a graduated circle, as seen in the figure. It is obvious, that a very slight variation in the height of the mercury at o, will be indicated by a considerable motion of the index, and thus changes in the weight of the atmosphere, hardly perceptible by the common barometer, will become quite apparent by this." —Comstock, 1850

Wheel Barometer

"The whole length of the tube of the wheel barometer, from C to A, is 34 or 35 inches, and it is filled…

"Rotation of a Wheel. The same force which throws the wire away from the mercury, will cause the rotation of a spur-wheel. For this purpose the conducting wire, instead of being suspended, as in the former experiment, must be fixed firmly to the arm. A support for the axis of the wheel may be made by soldering a short piece to the side of the conducting wire, so as to make the form of a fork, the lower end of which must be flattened with a hammer, and pierced with fine orifices, o recieve the ends of the axis." —Comstock, 1850

Wheel Rotation

"Rotation of a Wheel. The same force which throws the wire away from the mercury, will cause the rotation…