68 ILLINOIS ACADEMY OF SCIENCE 
The electric power for rotating the sphere and the light 
for illuminating the interior are controlled from within the 
Sphere. The electric current necessary for representing the 
Sun is received at the north pole at a rotary contact, and 
carried by an insulated wire to the ecliptic, about which there 
is a wire on the inside of the sphere. 
The Fixed Stars 
The stars are represented by tiny perforations in the 
sphere. Different sized perforations have been made to repre- 
sent stars of different magnitudes. The size and location 
of each star in the sphere has been determined with great 
care by using an instrument especially constructed for this 
purpose, so that the sphere is an accurate miniature represen- 
tation of the heavens. 
The Planets 
The shifting positions of the planets Jupiter, Saturn, 
Mars and Venus among the constellations have been provided 
for by a number of openings made to represent the different 
positions of each of these planets at different times of the 
year. The openings not in use are very readily covered. 
The Sun and Moon 
The Sun is represented by a small electric light which 
may be moved from place to place along the ecliptic and thus 
be kept in its appropriate place among the stars. The Moon 
will be represented by a series of small discs cut to represent 
discs may be moved from point to point along the orbit of the 
Moon and thus represent that body in its appropriate position 
in the heavens. 
Each star in the sphere has been numbered and a series 
of star tables have been prepared so that it is perfectly simple 
for one to identify a particular satr observed in the sphere 
or to locate a given star or constellation . 
This appartus should prove to be of great practical value 
in educational work. The public and private school children 
should make frequent visits to the sphere and the students in 
Astronomy in the neighboring Universities will find it well 
worth their time to arrange excursions with their instructors 
to the Academy to make use of this apparatus in their studies. 
