THE PROGRESS OF SCIENCE 



103 



museum. It was constructed, installed 

 and presented to the academy by Mr. 

 La Verne W. Noyes, president of the 

 board of trustees, in order to broaden 

 and to promote the educational and 

 scientific work of the academy. 



The material used in constructing 

 the sphere is light galvanized sheetiron, 

 which has been pressed to the proper 

 curvature and soldered to the equatorial 

 ring and to a smaller ring about the 

 entrance to the sphere. The platform 

 and horizon table are of wood and rest 

 upon a steel frame. The diameter of 

 the sphere is fifteen feet. The weight, 

 exclusive of the platform, is a little 

 more than 500 pounds. This weight is 

 caried by a 2$" tube attached to the 

 outside of the sphere along the line of 

 the equator and resting upon three 

 wheels as shown in the cross section 

 view. The two lower wheels carry the 

 greater portion of the weight, but the 

 third and upper wheel, above the door, 



resists a certain thrust due to the in- 

 clined position of the sphere. The sta- 

 tionary platform within the sphere is 

 supported in part by steel trusses rest- 

 ing upon the framework of the museum 

 balcony, and in part by two upright 

 pillars which rest upon the great I beam 

 of the main floor of the museum. This 

 platform carries a circular horizon table, 

 below which the sphere is obscured from 

 view, and above which there is a com- 

 plete hemisphere on which the stars are 

 represented. 



The observer in this sphere is located 

 on the surface of the earth at north 

 latitude 41° 50'. Celestial spheres con- 

 structed for localities having other lati- 

 tudes north or south would be placed at 

 other angles and certain other constel- 

 lations would be shown. The stars are 

 represented by tiny perforations in the 

 sphere, different sizes being used for 

 stars of different magnitudes. The size 



North-south Cross 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. Horizon Tabie. 9. Observers' Platform. 10. Switch Board. 11. Electric Wire. 

 12-13. Ecliptic or apparent path of the sun. 



