343 All Astronomical Machine, the Tellurium. 



round the sun. The wheel A contains 293 teeth, and the pin- 

 ion which belongs to the wheel B contains 8 leaves, consequently 

 B must make 36f turns during one turn of the wheel A. The 

 wheel B contains 80 teeth, and the pinion C contains 8 leaves ; 

 consequently C must make ten turns during one turn of the wheel 

 B, and ten times 36| or 366^ turns during one revolution of the 

 wheel A, that is, in one year. The little wheel upon the upper 

 end of the axis of the pinion C contains the same number of 

 teeth as the pinion o, therefore the earth must turn on its axis in 

 the same time as the pinion C ; it must make 366^ diurnal rota- 

 tions in a year, each rotation being performed in a sidereal day or 

 23h. 56m. 4s. The wheel E contains 167 teeth, and the wheel 

 O contains 25 teeth. Consequently O, and also the wheel P, 

 must make 6|| turns during one turn of E. The wheel P con- 

 tains 72 teeth, and the wheel D contains 36 teeth, consequently 

 D must make two turns during one turn of P, and twice 6i| or 

 1^2% turns during one turn of the wheel E, or in one year. As 

 the circular brass plate c is fixed upon the socket of the wheel 

 D, this plate must turn with the wheel and carry the moon V 

 13/3- times round the earth U in a year, which is equal to the 

 number of the moon's sidereal revolutions in this time. The 

 teeth of the wheel G act upon the teeth of the wheel F, The 

 wheel G contains 20 teeth, and the wheel F contains 372 teeth, 

 consequently G must make 18 j% turns, while F turns once round. 

 As the wheel G makes but one turn on its axis in a year, the 

 wheel F must require IS/^ years to perform a revolution. The 

 oblique plate d, to which the moon's orbit is parallel, being fixed 

 upon the socket of the wheel F, the plate must turn with this 

 wheel and carry the moon's nodes round contrary to the order of 

 the signs, so as to perform a sidereal revolution in IS/^ years. 

 The teeth of the wheel I act upon the teeth of the wheel r, 

 which, as before stated, transmits motion to the wheel H. The 

 wheel I contains 20 teeth, and the wheel H contains 177 teeth, 

 consequently I must make 8|| turns in order to turn F round 

 once. As the wheel I makes only one turn in a year, the wheel 

 H must be 8^-^ years in performing a revolution. The index e, 

 which is fixed upon the socket of H, must turn with this wheel 

 and also perform a revolution in 8|^ years, which is the time in 

 which the moon's apogee performs a sidereal revolution ; there- 

 fore, this index will show the proper motion of the apogee. 



