magnitude and the Milky Way. The stars are rendered luminous by 

 the action of the Alpha particles of Radium upon a responsive base 

 of sulphide of zinc. The prepared material is cemented to small cel- 

 luloid disks of varying diameters, mounted in their respective places 

 on black mats. With little study of these maps the well known stars 

 and the Constellations can be readily located in the heavens. 



The other section contains a large collection of photographic 

 transparences, the finest results of the Mt. Wilson Observatory. They 

 are framed and illuminated by electric lights prepared with special 

 dies and reflectors. The photographs of the Moon are shown with 

 white light; those of the Sun have a yellow tint and those of the 

 nebulae, stars, clusters, spirals and comets have a soft blue light, giv- 

 ing them the exact appearance seen through a large telescope. 



There is also in this underground vault a cabinet upon which are 

 mounted three stereoscopes presenting beautiful astronomical stereo- 

 scopic photographs of the Moon, comets, meteors and other bodies 

 of the heavens. 



Upon the ground floor is neatly shelved a large and valuable 

 geological library, and upon exhibit, a collection of siderites or iron 

 meteors. The largest weighs 357 pounds and another turns down the 

 scales at seven and one-half pounds. These were obtained at Meteor 

 crater near Canon Diabolo, Arizona. The others are fragments from 

 that greatest known meteor, brought by Admiral Robert E. Perry 

 from Cape York, Greenland, and now deposited in the National His- 

 tory Museum, New York City. 



Upon the second floor are the Astronomical library of about 100 

 bound values of recent publications, perhaps 200 pamphlets and 

 magazines, maps and atlasses, over 500 photographic prints covering 

 many departments of astronomical work and more than 1100 lantern 

 slides, the finest results from the Mt. Wilson, Yerkes, Lick, Lowell 

 and Harvard Observatories. 



Suspended from the ceiling are models of the planets of our Solar 

 system made to a scale v/ith a circular ring upon the floor, almost 41 

 feet in circumference, representing the Sun. Mercury appears by a 

 small globe less than half an inch in diameter and the distance 

 across the rings of Saturn is more than 30 inches. The model of the 

 Earth is less than an inch in diameter and that of the Moon less 

 than a quarter of an inch. The models are painted in colors and they 

 appear as realistic as the planets themselves, seen through a good 

 telescope. 



A planetarium, showing the weekly positions of the planets and 

 demonstrating many astronomical facts relating to the Earth, Sun 

 and Moon, their positions and motions, and models of the double- 

 star systems, are seen on the floor. The walls, as well as those of 

 the other floors are covered with the very finest of astronomical 

 photographs and apparatus for demonstration. 



The third floor supports the observing room and the Dome. LTpon 



49 



