An Astronomical Machine, the Tellurium. 341 
plate d by means of its own gravity, and slides along this plate 
as ¢ turns round, the wire alternately rising and falling in its ~ 
socket ; consequently the orbit in which the moon V moves must 
always be parallel to the plate d, and form an angle of 54 degrees 
with the plane of the ecliptic. ‘The index e, which points to the 
moon’s apogee, is fixed upon the socket of the wheel H. The 
axis g carries four wheels A, EK, G, and I, which all turn as one 
wheel. Next to the wheel A is placed the pinion of a wheel B, 
whose teeth act upon the teeth of a small wheel p, which trans- 
mits motion to the pinion C. The teeth of the wheel E act 
upon the teeth of the wheel O, whose axis also carries a wheel 
P, which gives motion to the wheel D. The teeth of the wheel 
G act upon the teeth of the wheel F'; and lastly, motion is trans- 
mitted from the wheel I to the wheel H by means of an inter- 
vening wheel r. 
When the winch m is turned by a steady hand, the leaves of 
the pinion N act upon the teeth of the large circular wheel M, 
and turn it and the elliptical L on their common axis with an 
equable motion. The teeth of Lat the same time act upon those 
of the wheel K. As K turns, the arms # and # both move in the 
same direction and carry the movable frame 567 8 parallel to 
itself, over and over the top of. the large stationary frame 1 2 3 4. 
The earth U is carried along with the moving frame, and has the 
parallelism of its axis also rigidly preserved. As the ends of the 
axes f and g slide round in the elliptical grooves, in the board 1, 
it is apparent that the orbit described by the earth U, must be an 
ellipsis of the same size and eccentricity as either of these grooves. 
When the earth is in its perihelion, as represented in the draw- 
ing (Plate V,) that part of the circumference of the elliptical 
Wheel L, which is farthest from its axis and has the greatest ve- 
locity, is applied to a part of the circumference of K which is 
nearest to the axis of the latter wheel, consequently the earth 
must have its quickest motion. When the earth comes to its 
aphelion, these elliptical wheels have a reverse position with re- 
Spect to each other, which gives the earth its slowest motion. 
These elliptical wheels working together in this manner, give the 
earth U the same unequable motion in its orbit, that the real 
earth has in nature. 
The wheels A, E, G, and I, all make one complete turn on 
their common axis g during an entire revolution of the earth 
