368 



THE GUIDE TO NATURE 



sional demonstrator was kept on duty came with an instructor or by special 



day and night. Visitors in groups of arrangement with the secretary of the 



twenty or thirty were taken into the Academy. This has resulted in a 



sphere and after the demonstration, thoughtful, educational use of the 



which took about twenty minutes, an- sphere, and today many of the teach :rs 



NORTrr-SOUTH SECTION OF SPHERE. 



1-2. South Polar Ring at entrance. 



3. Upper Wheel supporting sphere. 



4. One of two lower wheels which support the 



sphere and are propelled by motor. 



5. Electric Motor. 



6. North Pole of the heavens. 



7-8. Horizontal Table. 

 9. Observers' Platform. 



10. Switch Board. 



11. Electric Wire. 



12-13. Ecliptic or apparent jiath of the 



other group was admitted. This popu- in Chicago make regular pilgrimages to 



lar, general demand was however, not the Academy, and with the help of the 



what the Academy desired to encour- sphere demonstrate to their chil 'ren 



age. Therefore, the use of the sphere their simple lessons in descriptive as- 



was limited to student parlies that tronomy. 



