The Practical Astronomer / Comprising illustrations of light and colours--practical descriptions of all kinds of telescopes--the use of the equatorial-transit--circular, and other astronomical instruments, a particular account of the Earl of Rosse's large telescopes, and other topics connected with astronomy - Thomas Dick

For the revolution of Juno, the yearly axis C is furnished with a wheel of 54 teeth, which impels a wheel of 50 teeth on axis B, to which is made fast a wheel of 27 teeth which turns a wheel of 127 teeth on axis A, once round in 1590 days 17^h 35^m 2.7^s, and the tube of which ascends on that of Vesta, and supports a horizontal arm which carries a small ball representing this planet in the period named.

CERES’ PERIOD.

The revolution of Ceres is derived from the period of Juno, because wheel-work taken from the unit of a solar year was not sufficiently accurate for the purpose, therefore on Juno’s wheel of 127 teeth is fixed a wheel of 123 teeth, which drives a thick little bevel sort of wheel of 30 teeth on axis B: the reason of this small wheel being bevelled is to allow its teeth to suit both wheels ¹²³/₁₃₀; wheel 30 drives wheel 130, on axis A once round in 1681 days, 6^h 17^m 22.4^s and the tube of wheel 130 turns on the tube of Juno, and ascends in a similar manner with the rest and carries an horizontal arm supporting a small ball representing this planet, and is caused to revolve round the Sun in the above mentioned period (the period of Ceres to that of Juno is as 130 is to 123; hence the wheels used.)

PALLAS’S PERIOD.

The Period of Pallas could not be derived from the solar year with sufficient accuracy, and recourse was had to an engrafted fraction on the period of Ceres, thus. On wheel 130 of Ceres is made fast a wheel of 122 teeth, which drives a wheel of 81 teeth on axis B, to which is fixed a wheel 79 which impels a wheel of 119 teeth on axis A, and is furnished with a tube which ascends, and turns on that of Ceres, and supports a horizontal arm, which bears a small ball representing this planet, which by virtue of the above train of wheels is caused to complete a revolution round the Sun in 1681^d 10^h 28^m 25.1^s.

JUPITER’S PERIOD.

The motion of this planet is derived from the period of a solar year; from the ‘yearly axis’ thus, on this axis is made fast a wheel of 44 teeth which turns a wheel of 94 teeth on axis B, to which is riveted a small wheel of 20 teeth, which impels a wheel on axis A having 111 teeth, which is furnished with an ascending tube which revolves over that of Pallas, and bears an horizontal arm which supports a ball representing this planet, which by the said train of wheels is caused to revolve round the Sun in 4330^d 14^h 39^m 35.7^s.

SATURN’S PERIOD.

The periodic revolution of Saturn is also taken from the solar year—viz., a small wheel of 17 teeth is fixed to the ‘yearly axis’ near its top, and drives a wheel of 129 teeth on axis B, to which is made fast a wheel of 49 teeth, which turns a wheel of 190 teeth on axis A, whose tube ascends and revolves on that of Jupiter’s tube, and supports an arm, having a ball representing Saturn and its rings, and which by the train of wheels is caused to perform a revolution round the sun in the period of 10746^d 19^h 16^m 50.9^s.

URANUS’S PERIOD.