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Til E GUIDE TO NATURE 



The 100-Inch Telescope at Mount Wilson. 



By Jennie B. Lasby, In Popular Astronomy. 



After nearly nine years of continuous 

 work the mirror for the ioo-inch tele- 

 scope has been finished and is in its 

 mounting' at the summit of Mount 

 Wilson. Since this is the greatest 



old town with its huge glass factories 

 is now in ruins and what remains is 

 in the hands of the Germans. The 

 glass was packed just as it came from 

 the mold and shipped to Galveston by 



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triumph of the optician's skill it may be 

 of interest to the readers of this maga- 

 zine to review its history. 



The disc from which the mirror was 

 fashioned was cast, early in 1908, in the 

 factory at St. Gobain, France. This 



water and from there transported to 

 the workshops at Pasadena, where a 

 building had been erected especially 

 for the work of grinding and polishing. 

 The glass in its rough state weighed 

 about five and one-half tons, was 101 



