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"A small projection in machinery, used to impart motion. <em>C. wheel</em>, a wheel having cogs on its circumfrence." &mdash; Williams, 1889

Cog-wheel

"A small projection in machinery, used to impart motion. C. wheel, a wheel having cogs on its…

An illustration of cogging.

Cogging

An illustration of cogging.

"It is found preferable, therefore, when a great difference of velocity is required, to use a combination of wheels, of moderate size. In the following figure, three wheels are seen thusly connected." &mdash; Goodrich, 1844

Gears

"It is found preferable, therefore, when a great difference of velocity is required, to use a combination…

A pinion and spur gear meshed together.

Gears

A pinion and spur gear meshed together.

"2 wheels revolving in contact, but in different planes, so as to transfer motion from one plane to another." &mdash; Williams, 1889

Mitre-wheels

"2 wheels revolving in contact, but in different planes, so as to transfer motion from one plane to…

"Endless screw, a mechanical arrangement consisting of a screw the thread of which gears into a wheel with skew teeth, the obliquity corresponding to the angle of pitch of the screw." -Whitney, 1911

Endless Screw and Wheel

"Endless screw, a mechanical arrangement consisting of a screw the thread of which gears into a wheel…

"a, scroll-wheel, intermeshing with the pinion b, which, sliding by a feather on the shaft, c, imparts a gradually decreasing velocity to the latter as b is moved toward the center of a." -Whitney, 1911

Scroll Wheel

"a, scroll-wheel, intermeshing with the pinion b, which, sliding by a feather on the shaft, c, imparts…

"A wheel having teeth projecting radially from the circumference." &mdash; Williams, 1889

Spur-wheel

"A wheel having teeth projecting radially from the circumference." — Williams, 1889

"System of Wheels.&mdash;As the wheel and axle is only a modification of the simple lever, so a system of wheels acting on each other, and transmitting the power to the resistance, is only another form of the compound lever. The first wheel a, by means of the teeth, or cogs, around its axle, moved the second wheel, b, with a force equal to that of a lever, the long arm of which extends from the center to the circumference of the wheel, where the power p is suspended, and the short arm from the same center to the ends of the cogs. The dotted line c, passing through the center of the wheel a, shows the position of the lever, as the wheel now stands." &mdash;Comstock, 1850

System of Wheels

"System of Wheels.—As the wheel and axle is only a modification of the simple lever, so a system…